Experimental progress with ultracold atoms has allowed the study of many-body systems far from thermal equilibrium in accessible timescales when compared with solid state systems [1–5]. Moreover, atomic gases offer unique advantages for the control of many of relevant parameters, like the tuning of interactions and the change of internal state, those that have allowed the experimental...
Optical atomic clocks are the most precise and accurate measurement devices ever constructed, reaching fractional systematic uncertainties below one part in $10^{18}$ [1]. Their exceptional performance opens up a wide range of applications in fundamental science and technology. The extreme properties of highly charged ions (HCI) make them highly sensitive probes for tests of fundamental...
Neutral atom arrays, trapped and arranged using optical tweezers and interacting with each other when excited to Rydberg states, constitute a rapidly evolving platform for quantum simulation and quantum computation. QuEra Inc. presents Aquila: a 256-qubit cloud-accessible machine, with a connectivity that is programmable by the user via their arrangement in 2D, enabling the encoding of...
If a resonant photon traverses a medium and is transmitted on the far side, does it excite any atoms along the way? Previous work (PRX Quantum 3, 010314) provides evidence that it does. Since this work was limited to measurements using only broadband pulses of light, it cannot distinguish between recent theories that make strikingly different predictions in the case of excitation with...
Luis. A. Peña Ardila
Institut für Theoretische Physik, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover, Germany
Breakthrough experiments have newly explored the fascinating physics of dipolar quantum droplets and supersolids. The recent realization of dipolar mixtures opens further intriguing possibilities. We show that under rather general conditions, the presence of a second...
Can one detect a tunneling particle inside of a barrier? Traditional quantum measurement of the position of a tunneling particle inside a barrier transfers significant energy to the particle, precluding observation of a tunneling particle while it is in the ‘forbidden’ region. Instead, one might probe a tunneling particle ‘weakly,’ so as to prevent energy transfer, as envisioned by a weak...
My poster will present a cavity QED experiment where we use $^6$Li atoms to perform quantum simulations of random spin models.
The atom-cavity system realizes a spin chain with random transition frequencies coupled to an extended photon mode, with controlled disorder realized by a local light-shift of the excited state of the atoms. We study the competition between the collective many-body...
Laboratory measurements of cold ion-molecule collisions help to develop understanding of the dynamics and kinetics of interstellar chemistry. In our linear Paul ion trap, we trap ions at cold temperatures and react them with neutral molecules in an isolated environment. The products and branching ratios of these reactions are measured with high resolution with a time-of-flight mass...
We experimentally and theoretically investigate collective effects in a one-dimensional array of cold atoms coupled to a single-mode optical nanofiber [1]. Our analysis unveils the microscopic (i.e., atom per atom) dynamics of the system, showing that collective interactions gradually build-up along the atomic chain in the direction of propagation of the excitation light pulses. Our...
Rydberg atom arrays are a promising platform for quantum information and quantum computation. However, they lack a photonic link, such as an optical cavity, which could be used for fast non-destructive readout for error correction or for remote entanglement of distant arrays, thus extending the computational capabilities of the platform. The integration between an optical cavity and Rydberg...
The detection of phase transitions in quantum many-body systems with lowest possible prior knowledge of their details is among the most rousing goals of the flourishing application of machine-learning techniques to physical questions. Here, we train a Generative Adversarial Network (GAN) with the Entanglement Spectrum of a system bipartition, as extracted by means of Matrix Product States...
Cooling of positronium (Ps), an electron-positron bound state, leads to important research such as precision measurements of energy intervals or realizing Bose-Einstein condensation. The current coldest limit of Ps, which was achieved by thermalization with cooled solid, is still over 100 K [1]. Laser cooling and other cooling methods are under intense research to give a breakthrough in this...
Positronium (Ps), a bound state of an electron and a positron, is a purely leptonic and anti-particle system. Preparing a cold gas of Ps leads to precision spectroscopy and a realization of Bose-Einstein condensation of exotic atoms. Owing to the nature of the particle-antiparticle pair, Ps has a finite lifetime of 142 ns. Therefore, developing a rapid cooling method is the key to cool Ps...
We describe our progress in developing a proof-of-principle hybrid quantum repeater based on laser-cooled caesium ensembles and a semiconductor quantum dot. The atoms here can be used as a quantum memory or as a non-linear medium whilst the quantum dot can be used as a bright source of entangled photon pairs. The laser cooled atoms are loaded inside a hollow-core fiber to achieve an optical...
Recently, the formation of heteronuclear quantum droplets has been observed in an attractive bosonic mixture of $^{41}$K and $^{41}$Rb. [1], with increased lifetimes with respect to the homonuclear mixture of $^{39}$K. In order to enable fruitful comparison with experiments, we have performed a study of the $^{41}$K and $^{41}$Rb mixture using the diffusion Monte Carlo method and the Density...
The blackbody radiation (BBR) Stark shift currently limits the performance of many atomic frequency standards. It constitutes the largest uncancelled shift and the leading uncertainty in the most accurate optical lattice clocks [1,2]. One attempt to tackle this limitation has been to create a well-characterized BBR environment at room temperature [3]. However, the uncertainty on the atomic...
With a specially designed coil [Rev. Sci. Instrum. 92, 093202 (2021)], we quench the interaction strength of an ultracold cloud of $^6$Li atoms instantaneously, i.e. faster than the Fermi time. In the short time dynamics following the quench we observe first indications of an oscillation in the condensate fraction reminiscent of the Higgs-mode.
The...
Two-component Fermi gases with imbalanced spin populations feature mismatched Fermi surfaces which can lead to a range of novel behaviours. Here, we produce and study spin-imbalanced Fermi gases following a quench which removes a fraction of the atoms in one spin state, from an initially balanced spin-mixture. We apply this approach to harmonically trapped lithium-6 gases and measure the...
Improved measurements of the electron electric dipole moment (eEDM) will strongly constrain the parameter space of new physics theories. Over the last decade, polar molecules have become established as the most promising systems for eEDM searches, due to the large internal electric fields experienced by an eEDM in these molecules. The sensitivity of eEDM searches is determined by the coherence...
On-demand sources of non-classical light play an important role in quantum information and metrology [Ref. 1], and semiconductor quantum dot (QD) sources promise high-quality and efficient single and entangled photons [Refs. 1, 2]. At the same time, other states of light have been observed in the QD emission [Refs. 3, 4, 5, 6] as the nature of the emitted light relates with the dynamics of the...
Arrays of ultracold polar molecules exhibit long-range, long-lived dipole-dipole interactions that can be harnessed for the quantum simulation of matter, quantum computation, and precision measurements. Crucial to many of these proposals is the ability to produce adjacent pairs of molecules whose quantum states we can individually control. To that end, we detect vacancies in arrays of...
The time evolution of a quantum system can be strongly affected by dissipation. Although this mainly implies that the system relaxes to a steady state, in some cases it can make new phases appear and trigger emergent dynamics. In our experiment, we study a Bose-Einstein Condensate dispersively coupled to a high finesse resonator. The cavity is pumped via the atoms, such that the sum of the...
Dynamic transients are a natural ingredient of out-of-equilibrium quantum systems. One paradigmatic example is Dicke superradiance, describing the collectively enhanced population inversion of an ensemble of two-level atoms coupled to a single mode of the electromagnetic field.
Here, we present a new approach exploiting superradiance to engineer dynamical tunneling in a synthetic lattice...
Radical polyatomic molecules can be produced from gas-phase atomic metal precursors in the presence of a reagent gas. Previous work with YbOH [1] and CaOH [2] has shown that molecular production in a cryogenic buffer-gas cell can be enhanced more than ten-fold by populating metastable triplet electronic states of metal atom precursors. These demonstrations, while highly effective, required...
At the National Research Council Canada (NRC), an optical frequency standard based on a single trapped strontium ion has been developed. The optical clock uses the 5s $^2S_{1/2}$ – 4d $^2D_{5/2}$ electric quadrupole transition of the $^{88}\mathrm{Sr}^+$ ion at 445 THz as its reference transition. This clock transition of the $^{88}\mathrm{Sr}^+$ ion has been recommended as one of the...
Quantum electrodynamics (QED) is one of the most stringently tested theories underpinning modern physics. Nevdertheless, recent precision atomic spectroscopy measurements have uncovered several small discrepancies between experiment and theory. One particularly powerful experimental observable that tests QED independently of traditional energy level measurements is the tune-out frequency,...
The measurement of the electron electric dipole moment (eEDM), $d_e$, is a powerful probe of physics beyond the Standard Model. The current most stringent limit of $|d_e|<1.1\times10^{-29}\ \textrm{e}\cdot\textrm{cm}$ was reported by the ACME II experiment (Nature, 562(2018), 355). ACME III aims to improve this experimental limit by an order of magnitude. Progress has been made in...
In the vicinity of a Feshbach resonance only a hand full of length scales, such as the scattering length and the effective range, determine the observed physics. Few-body observables, such as recombination loss maxima and minima, are related to the underlying length scales via universal theories. In particular, the Efimov-van-der-Waals universality relates the position of the first three-body...
Arrays of neutral atoms have recently emerged as a competitive platform for quantum simulation and computation with many properties favorable for scaling. Rydberg states of atoms are often used because the strong Rydberg-Rydberg interactions can facilitate two-qubit gate operations and simulate many-body systems. However, for most schemes, readout of a Rydberg qubit is a destructive process...
Ultracold atomic gases can be used to simulate phenomena from condensed matter physics, such as the formation of polaron quasiparticles. However, at strong coupling a Bose polaron formed by an impurity atom in a Bose Einstein condensate (BEC) displays fascinating behavior quite distinct from the common condensed matter scenario. This is due to the possibility of bound state formation and the...
We are interested in the problem of light scattering by a dense ensemble of two-level atoms in a regime close to the Dicke regime, in which many atoms are trapped in a volume whose dimensions are smaller than the wavelength of the atomic transition. When the medium is dense and the frequency of the light is close to that of an atomic transition, the light-induced dipoles interact with each...
Dynamical Casimir effect (DCE) designates a plethora of phenomena characterized by generation of photons (or quanta of some other field) from vacuum due to time-dependent variations of the geometry (dimensions) or material properties (e.g., the dielectric constant or conductivity) of some macroscopic system. The circuit QED architecture is a handy platform for the implementation of DCE and its...
Atomic masses with high precision can be determined by Penning-trap mass spectrometry. The LIONTRAP experiment is one such high-precision mass spectrometer that can achieve relative mass uncertainties of the order of 10$^{−12}$ and is dedicated to light ions. Measurements on light ions are challenging due to the relatively large ratio of kinetic energies compared to the low rest mass.
The...
The development of novel quantum technologies ultimately depends on the ability to generate non-classical states. In this regard, the so-called "NOON states" - "all or nothing" superpositions - have been shown to enable interferometry at the "Heisenberg sensitivity" (with a scaling that is limited by nature itself). Much effort has been made to generate such states on several platforms, with...
I will present our activity on the realisation of atom interferometry with an optical clock transition beyond the standard quantum limit (SQL) with strontium atoms. An interferometer can be injected with entangled atoms to improve its phase resolution $\Delta \phi$, where the entanglement is created between momentum state superpositions by performing cavity-enhanced quantum non-demolition...
Laser-cooled molecules promise access to a diverse range of research directions from quantum simulation to controlled ultracold chemistry. Today, inefficient slowing of cold molecular beams remains a key barrier preventing molecular magneto-optical traps (MOTs) from trapping large, dense samples of ultracold molecules with properties similar to their atomic counterparts. Our experiment aims to...
We present our recent results on the fast loading of a dense magneto-optical trap (MOT) of Cd atoms from a pulsed cryogenic helium buffer gas beam. We can load more than $10^7$ atoms of each Cd isotope in less than 10 ms from a single atomic pulse and reach densities well above $10^{11}$ cm$^{-3}$ by using the strong transition in the deep ultraviolet near 229 nm. The Cd MOT serves as a...
In our group, we are interested in $^6$Li$^{40}$K molecules at their rovibrational ground-state, which posses a large $3.6~\text{Debye}$ absolute dipole moment. This makes them suitable for the quantum many-body simulation of anisotropic and long range interactions. In order to transfer the molecules from a weakly bounded Feshbach-state to their ground-state, the method to be used is...
The field of waveguide QED, where atoms (real or artificial) are coupled to one-dimensional waveguides, has attracted immense theoretical and experimental interest recently. However, despite the huge body of research, our understanding of the many-body regime consisting of many atoms and photons remains limited. This stems partly from the usual challenge of many-body systems – the...
Quantum machine learning (QML)---machine learning on quantum computers---is a rapidly developing, promising application of near-term quantum devices. Most present hardware implements the unitary circuit model of quantum computation. However, recently also measurement-based quantum computation (MBQC) has become technologically relevant, and progress is made towards MBQC with atomic systems. So...
Motivated by the extensive studies of measurement-only entanglement phase transitions in 1D, we implement a simple model of random non-commuting two qubit XX and ZZ measurements in 2D. We tune the probability of measuring XX and ZZ on horizontal and vertical bonds and use long range spin correlations as the order parameter. We find that when the system has subsystem symmetries, we get a second...
Resonance fluorescence spectrum of a two-level system consists of a single peak that evolves into a triplet structure, known as Mollow triplet , when it is driven by a radiation field above its saturation intensity. Particularly, photons originated from different peaks of the triplet show distinct photon correlations, which allows the fluorescence to be engineered as a useful light source for...
Our purpose is precision measurement of the 1S-2S energy interval in Muonium, which is an exotic hydrogen-like atom consists of a positive muon and an electron. This purely leptonic system enables a precise calculation of the energy interval with the Standard Model without any concerns of the uncertainty from the charge radius of the nucleus, unlike the hydrogen-atom. This advantage motivates...
Electric field sensors based on warm vapors of atoms excited to Rydberg states have distinguishing features that offer new application possibilities. A single sensor can operate over a wide spectrum of frequencies, from DC to THz, with a consistent instantaneous baseband bandwidth of approximately 10MHz. The sensor head containing the vapor is highly transparent and can also be small relative...
Recent experimental and theoretical works have reignited long-standing debates over the time taken for certain quantum transitions, such as tunneling, to occur. This is important, as tunneling is a common quantum phenomenon in molecular systems where nonadiabatic couplings are significant, and certain simulation methods struggle to accommodate its effects. Here we propose a new type of quantum...
The performance of optical atomic clocks has improved tremendously over the last two decades. The fractional frequency uncertainties of the best optical clocks reach the $10^{-18}$ level and currently outperform cesium fountain clocks, the current primary frequency standards defining the SI second, by two orders of magnitude. Redefinition of the SI second based on optical clocks is expected to...
Ultracold neutral atoms are an excellent test-bed for novel quantum control techniques due to their stability, and efficient coupling to fields in the radio, microwave, and optical regimes. Various control protocols which could be used in quantum information processing (QIP) may first be investigated in ultracold atoms to prove their efficacy before being generalized to other more established...
Spinor BECs are Bose-Einstein condensates (BECs) where all the spin states {$m_F=+1,0,-1$} of the atom are accessible [1]. These novel ultracold atomic systems can exhibit both ferromagnetic and antiferromagnetic order and thus offer enhanced opportunities for exploring phenomena beyond those accessible in scalar BECs, such as new classes of topological defects [2]. The polar core vortex (PCV)...
Molecules with optical cycling centers (OCCs) are highly desirable in the context
of fundamental studies as well as applications (e.g., quantum computing) because they can be effectively cooled to very low temperatures by repeated absorption and emission (hence, cycling). Charged species offer additional advantages for experimental control and manipulation. We present a systematic...
We study the Ramsey-type spectroscopy and the production of spin-squeezed states with ultra-cold atomic fermions described by the Fermi-Hubbard model in the Mott insulating regime. We show activation of two twisting mechanisms by a position-dependent laser coupling between internal degrees of freedom of atoms. A single laser coupling simulates the one-axis twisting model with the axis and...
Spin-polarized samples, spin mixtures and Feshbach molecules of quantum degenerate fermionic atoms are prepared in selected excited Bloch bands of an optical chequerboard square lattice. For the spin-polarized case, extreme band lifetimes above 10 s are observed, reflecting the suppression of collisions by Pauli’s exclusion principle. For spin mixtures, lifetimes are reduced by an order of...
Quantum gases of bosons and fermions behave as superfluids, and for parametric excitations, the sample exhibit Faraday Waves, which obey a Mathieu equation. Therefore, to generate them, we need to consider a periodic modulation in a parameter of the system, e.g., the trap frequencies or contact interaction. From the experimental point of view, these excitations are manifested in trapped gas...
Motional modes of trapped ions have been shown to be a useful tool for quantum sensing as well as a potential platform for performing continuous variable quantum computing (CVQC) [1,2]. Both applications require the ability to prepare well-defined motional states with high fidelity. These states can be generated without the use of laser fields which could reduce the experimental overhead in...
The Standard Model as we know contains insufficient sources of charge parity (CP) violation to explain the observed baryon asymmetry of the universe (BAU). Heavy polar molecules are a sensitive, tabletop platform for precision searches of CP-violating electromagnetic moments originating from Beyond the Standard Model (BSM) physics. The polyatomic molecule YbOH is a promising platform to...
Trapped ion devices make some of the best candidates for quantum information processors as they provide naturally identical qubits with long coherence times. One approach to scaling these systems is using large registers of ions. This can be achieved through implementing qubits in multiple atomic species, where each qubit type is insensitive to the others' light fields, eliminating scattering...
We report on the creation of sodium-cesium (NaCs) molecules in their rovibrational ground state [1], assembled from ultracold clouds of Na and Cs atoms [2,3]. Via one- and two-photon spectroscopy we have identified a pathway that allows us to produce the first ultracold ensembles of NaCs ground state molecules via stimulated Raman adiabatic passage (STIRAP). In the ground state we explore the...
The coupling of a two-level system with a field mode, whose fully quantized field version is known as the quantum Rabi model (QRM), is among the central topics of quantum physics and recent quantum information technologies. When the coupling strength reaches the field mode frequency, the full QRM Hamiltionian comes into play, where excitations can be created out of the vacuum.
We...
Lanthanide atoms provide a rich platform for a number of ultracold atom experiments due to their variety of available optical transitions, strong anisotropic interactions and the large spin space of their fermionic ground states [1]. Leveraging these properties alongside the large, programmable defect-free arrays of qubits that can be realised using optical tweezer arrays of Rydberg atoms...
Optically-pumped magnetometers (OPMs) are widely used for their scalar sensitivity, accuracy, and compact sensor packages, but require additional mechanical references for vector magnetometry. These mechanical references, such as a coil system, often limit the vector accuracy due to machining tolerances and drifts. Current approaches to improve vector accuracy are calibrations that involve...
Quantum sensing and quantum information processing use quantum advantages such as squeezed states that encode a quantity of interest with higher precision and generate quantum correlations to outperform classical methods. In harmonic oscillators, the rate of generating squeezing is set by a quantum speed limit. Therefore, the degree to which a quantum advantage can be used in practice is...
Although radio-frequency (r.f.) traps have been widely used in trapped-ion quantum information and simulation, they face some inherent challenges in scaling up the number of qubits. Precise alignment of static and r.f. field nulls is necessary to achieve confinement of the ions without r.f. driven motion. As the r.f. null is inherently 1-dimensional, attempts at scaling into 2-d are beset by...
Quantum simulations of lattice gauge theories in qubits require a truncation of the infinite dimensional Hilbert space. This alters the behavior of the model. However, recent progress in the control of bosonic qubits, which naturally host a large dimensional Hilbert space, points the way to efficient simulation of lattice gauge theories in $1+1$d that generalizes well to higher dimensions. We...
We present the design, implementation and characterization of a new dual-species cold atomic mixture of $^{39}$K and $^{23}$Na with a large number of atoms. The dual species Magneto Optical Trap (MOT) has more than 10$^{10}$ $^{39}$K atoms and 5$\times$10$^9$ $^{23}$Na atoms, which are simultaneously loaded using two independent 2D$^+$MOT with high cold atomic beam flux. The dual cold atomic...
A universal relationship between scaled size and scaled energy was explored in few-body systems$^{1,2,3}$. Ground-state self-binding energies were obtained by the diffusion Monte Carlo method. Obtained energies support generalized Tjon lines. Structural properties were extracted by pure estimators$^4$, which proved successful in evaluating theoretical predictions of distribution functions$^5$...
Ultracold atoms confined in optical lattices are a powerful platform for quantum simulation of complex many-body systems. We confine spin-1/2 atomic fermions ($^6$Li) to one dimension and realize the Yang-Gaudin model, the low-energy behavior of which is expected to be that of a Tomonaga-Luttinger liquid [1]. Such liquids exhibit bosonic collective low-energy excitations and spin-charge...
High-precision experiments to measure parity (P), and parity and time-reversal (P, T) violation using paramagnetic molecules are a promising route to look for physics beyond the Standard Model of particle physics. Using close-lying opposite-parity molecular states enhances the symmetry-violating experimental signals. This enhancement is purely relativistic and increases with the atomic number...
I will report on the first realisation of a very long and controllable synthetic dimension of atomic harmonic trap states [1]. To create this, we couple trap states by dynamically modulating the trapping potential of the atomic cloud with patterned light. By controlling the detuning between the frequency of the driving potential and the trapping frequency, we implement a controllable force in...
Arrays of neutral atoms offer a promising platform for building controllable and scalable quantum many-body systems. Atoms of the same species have identical transitions and are practically unlimited in supply. Given the maturity of the field of atomic physics, a large toolbox of advanced techniques for cooling and manipulating atoms is available. Atoms in ultra-high vacuum systems are also...
Ultracold atoms provide a unique playground for exploring many-body phenomena emerging in strongly correlated systems, owing to an exceptional control over Hamiltonians, their long coherence times, and recently established single-atom microscopy techniques. Here, I will report on the ongoing development of a new atom experimental apparatus in Trieste, aiming to control and detect ytterbium...
An optical atomic clock based on a single aluminum ion is holding the current world record for accuracy with a fractional frequency uncertainty below $10^{-18}$ [1]. This outstanding precision allows for novel applications like relativistic geodesy [2,3] on the cm level and helps to tighten the bounds for physics beyond the standard model [4]. But single ion clocks are impeded by their low...
Superradiant lasers are suitable as light sources with an ultranarrow linewidth. Superradiant emission can exhibit a linewidth, which is narrower than the natural decay on the same transition [1]. Like conventional lasers, superradiant lasers usually incorporate a cavity to mitigate the atom-light interaction. In the conventional case the emission frequency is strongly dependent on the cavity...
Cold atoms in lattices have appeared as good candidates to mimic the properties of electrons in solid-state systems and to simulate quantum materials. However, experimental techniques currently use optical lattices in the far-field. This limits the lattice spacing to λ/2 and gives an upper bound to the relevant energy scale (tunneling and interaction), making it difficult to enter deeply into...
Long-range Rydberg molecules are molecules in highly-excited electronic states where the binding results from the scattering of an almost free electron of a neutral atom within its orbit. In our lab, we have in recent years developed a detailed experimental and theoretical understanding of the binding in homo- and heteronuclear long-range Rydberg molecules [1]. Our experimental techniques...
Rydberg atoms, with their giant electronic orbitals, exhibit dipole-dipole interaction reaching the GHz range at a distance of a micron, making them a prominent contender for realizing ultrafast quantum operations. However, such strong interactions between single atoms have never been harnessed so far because of the stringent requirements on the fluctuation of the atom positions and the...
The energy of ultra-dilute quantum many-body systems is known to be a
universal function of the gas parameter $x = n a_0^d$, where n is the density,
a0 the s-wave scattering length, and d the dimensionality of the space (d =
1, 2, 3) [1]. The universal regime typically holds only at small x and
extends up to values no larger than 0.001 [2,3]. Beyond that point, specific
details of the...
Vacuum is one of the most interesting phenomena of the real world. A two-level atom, frequently treated as a qubit, when unavoidably touched by vacuum, is unstable on its excited level, even if it does not interact with any other system. All states except the ground state suffer from decay due to interaction with vacuum radiation modes. The atom falls to the ground state in asymptotic time...
Techniques to directly laser cool and trap molecules at ultracold temperatures have revealed a new path towards the full quantum control of a diverse range of species with a variety of internal structures. Our experiment will capitalize on this generality by directly laser cooling and trapping CH radicals for tests of ultracold organic chemistry. The low mass and blue optical transitions in...
Confined quantum gases in a toroidal-like potential can be studied by a variational method using the like-Gross-Pitaevskii equations. The variational approach determines the dynamics of the quantum cloud, as the evolution of the aspect ratio during the free expansion of the cloud and the collective modes. We adapted the variational method to parametrize on a curved surface and effective...
Trapped-ions are one of the most mature platforms for quantum computation and quantum simulation. In trapped-ion quantum simulators the spin-spin interactions are mediated by the collective motion of the ions in the crystal (phonons). We show that additional optical tweezer potentials can be used to engineer the phonon spectrum, and thus tune the interactions and connectivity of the ion...
Out-of-equilibrium atomic systems may be used to develop quantum thermal machines which operate continuously at steady state. At such small scales, the energy currents characterizing work and heat exchange with thermal reservoirs exhibit fluctuations large enough to play a significant role in evaluating machine performance. I introduce here a novel set of bounds on the performance of...
I will present a new programmable quantum simulator based on Rydberg strontium atoms trapped in optical tweezers arrays at CNR-INO and LENS in Florence. This new experimental setup, supported by an infrastructural program of CNR, is now under construction in our laboratories as a joint effort of CNR and the University of Florence.
I will present the main features of the apparatus, including...
We have developed a relatively simple and compact Sr experiment designed for cavity QED with Sr atoms in a miniature ring resonator. The vacuum setup has a total length of 40cm including oven, Zeeman slower and glass cell, and routinely produces 2x10^7 87Sr atoms in the MOT with an oven temperature of 440°C. The slower does not require magnetic coils on its own as it exploits the far field of...
Single ions and atoms are interesting systems for single-photon detection due to their frequency selectivity and very low dark counts [2,3]. These capabilities are useful for any application in which a very low power signal must be detected against a broadband background. An example of such an application would be free-space quantum communication in daylight.
In this work, we present and...
Many sectors of society and the economy are now heavily reliant on Global Navigation Satellite Systems (GNSS). However, GNSS has several underlying vulnerabilities and cannot be used under- water or underground. In these situations, Inertial Navigation Systems (INSs) can act as a reliable alternative. These self-contained devices reconstruct the trajectory of a vehicle being tracked by...
Atomic data have received a great deal of attention, due to their need for the upcoming ITER project (International Thermonuclear Experimental Reactor). So, extensive spectroscopic studies both experimental and theoretical have been performed in the last years in order to estimate the power loss from the impurities in the forthcoming fusion reactors. Accurate values of wavelengths and their...
The standard model predicts that the electron’s electric dipole moment (eEDM, $d_e$) is too small to measure with current technology [1]. Theories that extend the standard model, however, predict much larger values, often exceeding $10^{-29}~e~\text{cm}$. With the current experimental upper limit set at $|d_e| < 1.1 \times 10^{-29}~e~\text{cm}$, [2] we can expect that improved measurements...
Free-space optical time transfer is a key enabling technology for intercontinental comparisons of optical atomic clock time scales and the eventual redefinition of the SI second. However, full realization of their potential for femtosecond-level intercomparisons requires ground-to-space (and possibly space-to-space) link operation. We present a series of long-range atmospheric channel...
In this theoretical work we describe the evolution of an atomic array driven by broadband squeezed light. Photons in a squeezed field are created as correlated pairs, thus leading to a phase-sensitive amplification and deamplification of fluctuations. These fluctuations depend on the squeezing mechanism and the spatial structure of the modes carrying the correlated pairs [1-3]. By spreading...
In a non-reciprocal optical amplifier, gain depends on whether the light propagates forwards or backwards through the device. Typically, one requires either the magneto-optical effect, a temporal modulation, or an optical nonlinearity to break reciprocity. By contrast, here, we demonstrate non-reciprocal amplification of fibre-guided light using Raman gain provided by spin-polarized atoms that...
Using a Rydberg atom-array quantum simulator, we experimentally demonstrate new applications which become possible through verifiable quantum evolution. At the outset, we show experimental benchmarking of system sizes with up to 60 atoms, and demonstrate new techniques in approximate verification beyond the classical simulation threshold. Further, we show how such benchmarking allows us to...
A theoretical analysis of the low energy surface excitations of quantum droplets formed by binary mixtures of ultracold dilute Bose gases is performed. Reliable expressions for the surface tension of the droplets are introduced based on the Thouless variational theorem. The Weber number can then be calculated as a measure of the relative importance of the inertia of the fluid in terms of...
Programming irreversible dynamical rules of cellular automata into non-unitary interactions of quantum systems appears to be a promising route to studying novel collective effects. Considering a master-equation embedding of classical cellular automata, we first investigate the unexplored area of computability aspects of Markovian quantum dynamics. We introduce a novel dynamical class of open...
Understanding how and at which speed information spreads in a quantum many-body system is a fundamental and intriguing question of quantum information science. Quantum metrology harnesses quantum entanglement for enhancing the precision of atomic sensors beyond the standard quantum limit. What do these apparently different fields of quantum mechanics have in common? We experimentally show that...
The development of fully controlled quantum systems in the laboratory has seen tremendous progress in recent years. One experimental platform which has shown to allow for an excellent level of control are trapped atomic ions, stored in linear radio-frequency traps. Here, one-dimensional chains of up to several tens of ions have already been employed successfully to carry out quantum simulation...
We apply correlation function analysis for a study of strong field ionization of atoms. We show that the study of the correlations of electron's coordinate and velocity reveals patterns which can be naturally interpreted as manifestations of the electron's barrier exit point (the spatial point where the electron exits the tunneling barrier). This analysis provides an unambiguous definition of...
Dipolar interactions are fundamentally different from the usual van der Waals forces in real gases. Besides the anisotropy the dipolar interaction is nonlocal and as such allows for self organized structure formation [1]. In 2015 we could observe the formation of a stable droplet crystal and found that this unexpected stability is due to beyond mean-field quantum corrections of the...
We present on various experiments utilizing quantum $^{39}$K gases trapped in a 3D optical box for investigations of few-body, many-body and far-from-equilibrium phenomena. The first result we present is a comprehensive characterization of F=1 manifold Feshbach resonances for magnetic fields up to 600G using loss spectroscopy and atom-dimer interferometry; these precision measurements enable...
The influence of inhomogeneous electric fields in ion clouds on high-angular-momentum Rydberg states is investigated. The fields follow from a superposition of macroscopic and random microscopic (Holtsmark) fields. The ion clouds are induced experimentally by photo-ionizing cold rubidium atoms in the $5D_{3/2}$ state near the focal spot of a near-concentric 1064-nm intracavity optical lattice....
Optically trapped polyatomic molecules are a promising platform for measurements of time-reversal symmetry violation due to their highly polarizable structure, co-magnetometer states, and long achievable coherence times [Kozyryev and Hutzler, PRL 119 (2017)]. For example, linear polyatomic molecules in the vibrational bending mode could be used to search for the electron’s electric dipole...
Building cold atomic quantum sensors with photonic structures promise to miniaturize the apparatus that could eventually lead to portable devices. To prepare atoms in photonic platforms to a temperature that can be applied as a sensor requires adopting free-space laser cooling in space-constrained photonic structures. Here, we demonstrate in-fiber Λ-enhanced gray molasses and delta-kick...
Assembly of rovibrational ground-state NaCs molecules in an optical tweezer array will allow for high-fidelity quantum computation and the exploration of rich dipolar exchange Hamiltonians. Currently, these systems are limited by a minimum tweezer separation, which sets a hard cap on the interaction strength and increases the characteristic time for interesting physics. Further, readout...
In resonance, pulse shapes have no effect on the population transfer; nevertheless, they affect the resonance response curves of the qubit. In this work, the experimental response curves of various pulse shapes were validated against the theoretical predictions. Furthermore, the effects of symmetrical cropping of the Lorentzian function at different heights were examined, using one of the...
We present detailed procedure and experimental setup to fabricate atomic vapor cell for atomic sensor application. A cell is 7.5 mm cubic with pyrex. The inner surfaces of the cell are coated with Aluminium Oxide. The cell is cleaned with distilled water, ethanol, and methanol respectively. The cell is baked in air at 550 degrees Celsius. The cell, then, is attached to high vacuum chamber with...
Laser cooling relies on photon cycling, which can be enabled in polyatomic molecules when an “optical cycling center” (OCC) is attached to an electronegative ligand. It was proposed that molecules with a (metal) alkaline-earth(I)-oxide-radical structure, would have good OCC properties and, thus, would be amenable to laser cooling [1]. More recent theoretical work has indicated that the...
In previous work, high precision eigenvalues for all states of
helium up to $n = 10$ and $L = 7$ have been obtained by the use of
double basis sets in Hylleraas coordinates [1]. In the present
work, we show that triple basis sets using three sets of
individually optimized nonlinear parameters for different distance
scales yield an order of magnitude improvement in accuracy for
basis sets...
THz imaging and THz technologies are of great interest for a variety of applications, including non-destructive testing and medical diagnosis. Here, we demonstrate a THz imaging setup that employs Cs Rydberg atoms as THz-to-optical photon converters to provide full field images at many thousands of frames per second, that can be captured with conventional optical cameras.1 The...
Rydberg ions have large dipole and quadrupole polarizabilities which makes them extremely sensitive to external electric fields [1],[2]. As a result, an ion in the Rydberg state experiences altered trapping potential which leads to motion-dependent Rydberg excitation energies [3]. Higher the Rydberg state more is the sensitivity to the electric quadrupole trapping fields. The oscillating...
Persistent currents in a ring are one of the most striking manifestations of a quantum system coherence. The periodic boundary constrains the wavefunction phase to wind in a loop of an integer multiple of 2$\pi$, which, when non-zero, gives rise to a current. Besides being a proxy of quantum phase coherence, persistent currents represent a cornerstone for many applications, from precision...
Cold antihydrogen, the bound state of an antiproton and a positron, is an ideal laboratory to test the fundamental CPT symmetry, one of the cornerstones of the Standard Model of particle physics, by comparing its energy levels to ordinary hydrogen. Hydrogen is one of the best studied atoms experimentally, among the two best-known transitions is the ground-state hyperfine transition...
Ultracold ground-state molecular quantum gases and mixtures yield highly complex and mostly unknown scattering behavior. In molecule-molecule collisions it ranges from the formation of long-lived four-body complexes to subsequent chemical reactions [1], photo-excitation [2] or spontaneous spin relaxation [3]. Atom-molecule collisions can give rise to tunable interactions such as Feshbach...
Generation of high power 121.6 nm light is vital for efficient laser cooling of antihydrogen. The nanosecond pulsed laser system developed for the ALPHA collaboration at CERN is presented here. It includes a high energy pulsed amplifier at 730 nm, followed by a doubling and subsequent gas phase third harmonic generation stage. We observe an anomalous frequency offset between the 730 nm seed...
Our experimental projects at the Laser Physics Institute (North Paris University) aim at characterizing entanglement for many-body systems made of large spin atoms. For this, we developed two experimental set-ups : one with large-spin strontium fermionic atoms, with spin-independent contact interactions; one with large-spin chromium bosonic atoms, with spin-dependent long-range dipole-dipole...
The electric quadrupole transition of the $^{88}$Sr$^+$ ion at 445 THz is one of 11 recommended optical transitions that can be used as secondary representations of the SI second. Progress towards the redefinition of the SI second using an optical clock indicates that a new definition will be based on either one atomic optical transition or an ensemble of such reference transitions, selected...
The Fermi-Hubbard model is an iconic model of solid state physics that is believed to capture the intricate physics of strongly correlated phases of matter such as High-Tc superconductivity. Such a state of matter is supposedly achieved upon doping a cold antiferromagnetic Mott insulator. Pairing of dopants (holes), in particular, is considered to be a key mechanism for the occurrence of...
Ultracold atomic gases play crucial roles in revealing nontrivial quantum transport phenomena. Especially, quantum transport of weakly-interacting Bose gases would be interesting in that the realizations with condensed-matter systems are difficult. In this poster, I focus on two-terminal transport systems with Bose-Einstein condensates. In spite of the formal similarity with fermionic...
The Ferdinand-Braun-Institute has been developing micro-integrated, high-power, narrow-linewidth semiconductor laser sources for precision spectroscopy applications for more than ten years. Starting with hybrid-integrated diode laser chips and micro-optics on a ceramic platform, we successfully enabled Bose-Einstein condensation experiments in a drop tower [1][2]. As the next step we now...
The ability to convert quantum signals between the microwave and optical domains is an important tool in quantum information processing. Here, we use a room-temperature ensemble of $^{87}{\rm Rb}$ atoms inside a microwave cavity to generate an optical signal whose frequency is the sum of an optical pump and a hyperfine microwave control field, using hybrid sum-frequency generation [1]. By...
We have developed a methodology for manufacturing alkali-metal vapour cells with internal confinement dimensions down to hundreds of nanometers (generally less than the probe laser wavelength). We envisage our nano-cells as a platform for fundamental atom-light interaction experiments, as well as for potential technological applications. Our manufacture process is versatile and our...
Nonclassical photon sources of high brightness are key components of quantum communication technologies. We here demonstrate the generation of narrowband, nonclassical photon pairs up to the ultimate limit of achievable generated spectral brightness at which successive photon pairs start to overlap in time.
Our biphoton source employs spontaneous four-wave mixing in an optically-dense...
A system of ultracold atoms can be brought in contact with a thermal bath by letting it interact weakly with a large cloud of another atomic species. We consider atoms in a time-periodically driven optical lattice in contact with an interacting Bose condensate and microscopically model them using Floquet-Born-Markov theory. The interplay of driving and dissipation will guide these systems into...
A fundamental tenet of quantum mechanics is that measurements change a system's wavefunction to that most consistent with the measurement outcome, even if no observer is present. Weak measurements produce only limited information about the system, and as a result only minimally change the system state. In this context, the interaction of a nearly closed quantum system with its environment can...
Ultracold atoms, made possible by laser cooling and trapping, are used as platforms for a wide range of applications such as observation of quantum degeneracy [1], quantum simulation [2], frequency standards [3] and ultracold collision studies [4]. While experiments using ultracold atoms of alkali metals and alkaline earth metals have made great progress, laser cooling has not been realized...
The calculations of different properties of the atoms and ions play a crucial role in many applications of various fields for instance, atomic physics, material science, astronomy, plasma, nanotechnology etc. An accurate description of different atomic properties is highly challenging with the standard approximations resulting in failure in providing the good data. Therefore, the surge for...
The The aim of CeNTREX (Cold molecule Nuclear Time-Reversal Experiment) is to search for the proton’s electric dipole moment by measuring the Schiff moment it induces in the $^{205}$Tl nucleus. We use the amplified energy shift from the Schiff moment that is present in the polar molecule thallium fluoride (TlF). To maximize the population of the science state, we employ rotational cooling on...
Recently, great progress has been made in direct laser cooling of molecules to temperatures close to absolute zero. However, experiments are limited by the number of molecules that can be captured from molecular beams using typical laser-based trapping methods. In Petzold et al. 2018, we proposed to transfer Zeeman deceleration to laser-coolable molecules and thus substantially increase the...
Measurements of heavy, polar molecules in the gas-phase are sensitive experimental probes of Parity (P) and Time reversal (T) violating new physics. The large internal fields and relativistic electron dynamics in these molecules amplify potential sources of P,T violating physics, such as the electron’s electric dipole moment (eEDM) or a nuclear magnetic quadrupole moment (NMQM). Molecular...
We theoretically investigate a bosonic Josephson junction by using the path-integral formalism with relative phase and population imbalance as dynamical variables. Starting from a Lagrangian of a Bose Josephson junction, we derive an action only in terms of relative phase by performing functional integration over the population imbalance. We then analyze the quantum only-phase action, which...
Alkaline earth atoms and optical tweezer arrays are naturally complementary technologies. The atoms provide convenient transitions for high fidelity optical cooling and imaging, well-controlled internal states with extremely high quality factors, and switchable interactions. The tweezers further provide programmable control over those atoms' motional states and positions. These capabilities...
Multi-messenger astronomy, the coordinated observation of different classes of signals originating from the same astrophysical event, provides a wealth of information about astrophysical processes. So far, multi-messenger astronomy has correlated signals from known fundamental forces and standard model particles like electromagnetic radiation, neutrinos and gravitational waves (GW). Many of...
Interactions in materials characterized by spin degrees of freedom play a crucial role in determining the magnetic properties both in the presence and in the absence of an external coherent drive. For instance, if the spin-dependent interaction is positive and strong as compared to the external drive the material behaves as a ferromagnet, otherwise it shows a paramagnetic response to external...
Two-photon transition rates are important in determining astrophysical quantities such as population balance in planetary nebulae. Our group recently calculated two-photon decay rates in heliumlike ions including the finite nuclear mass effects [1]. We have now perturbatively added relativistic corrections to these results, giving the most precise and accurate calculations to date for these...
In Point Source Atom Interferometry (PSI), a sequence of Raman laser pulses interact with an expanding ball of cold atoms, to split, redirect and recombine the matter-wave. It exploits the correlation between the position and velocity of the atoms to produce a spatially imprinted interference pattern across the atomic cloud. Since the phase of atoms contains information about inertial effects...
Highly-excited Rydberg atoms have been used for International System of Unit (SI)-traceable radio-frequency (RF) electric field and power measurements, but are limited in sensitivity to order 100 $\mu$V/m/$\sqrt{Hz}$ by noise and linewidth issues. These Rydberg atom-based sensors have far-reaching capabilities, ranging from SI-traceable measurements to receiving communication signals, even...
The pinning quantum phase transition can be observed in both weakly interacting quantum many-body systems described by a 1D Bose-Hubbard model and strongly interacting 1D systems modelled by Luttinger liquid theory. In both these cases an ultra-cold quantum gas can be driven to Mott-insulating state by imposing an infinitesimal small external lattice potential [1]
Recently an analogue to...
A measurement of the electron electric dipole moment (eEDM) is a powerful probe for the existence of physics beyond the Standard Model of particle physics. The ACME experiment searched for eEDM with the world's highest sensitivity using cold ThO polar molecules (Nature, 562 (2018) 355-360). One of the improvements for the next generation of the ACME experiment is using silicon...
In this poster, we report a quantum gas microscope of Lithium-7 atoms in a two-dimensional (2D) square lattice. Individual atoms in each lattice site are imaged by Raman sideband cooling in a hybrid potential of the 2D lattice and a single tightly focused optical sheet potential. With a high numerical aperture (NA=0.65) objective, we achieve a point spread function of 630nm (full width half...
Ultracold polar molecules are able to interact at long-range via electric dipole-dipole interactions, which can be used to generate entanglement between distant molecules by coherently coupling their rotational quantum states. This capability makes such molecules an attractive platform for simulation of quantum matter and for quantum computing. We present our recent work on coherent control of...
We investigate a system of dipolar atoms confined to move on a two dimensional plane. The dipole moments are all parallel and aligned in a direction that does not
necessarily coincide with the normal to the plane. As a result of the attractive and repulsive components of the dipole-dipole interaction, the system can form a self-bound system, which is stabilized by quantum fluctuations....
Understanding and tuning light-matter interactions at the level of single quanta is essential for numerous applications in quantum science. Such quantum control seeks to increase the small interaction cross section between single atoms and single photons. Exploiting cooperative response of subwavelength atomic arrays allows for realizing strong light-matter coupling even down to the level of...
A promising way to explore physics beyond the Standard Model of particle physics is doing high-precision measurements on molecules. One such measurement is the search for the P,T-violating electric dipole moment of the electron (eEDM). In diatomic molecules with one heavy atom, the effect of the eEDM is expected to be strongly enhanced, because of small rotational splittings and an enhanced...
We report progress towards a precise measurement of the isotope shifts in the $4^2$S$_{1/2} \rightarrow 3^2$D$_{3/2}$ 732 nm electric quadrupole transition in Ca$^+$. We perform correlation spectroscopy [1,2] on two co-trapped calcium isotopes. Simultaneous excitation of both ions using frequency sidebands derived from a single laser enables cancellation of common-mode laser phase noise and...
We study the dynamic response of bosons in a one-dimensional optical lattice and obtain the dynamic structure factor $S(k,\omega)$ for perturbations in the linear regime, as well as the non-linear response to strong density perturbations [1]. In our work, we use a continuous description of the system. Based on the time-dependent variational Monte Carlo method (tVMC) [2], we simulate the time...
Quantum phenomena that lead to the formation of long-lived collision complexes, such as scattering resonances play a central role in cold molecular collisions. These resonances are fundamental probes of the fine details of internuclear interactions and serve as a benchmark for current computational methods.
Here we present a joint experimental and theoretical study where we are able to...
Higher-dimensional topological phases play a key role in understanding the lower-dimensional
topological phases and the related topological responses through a dimensional reduction procedure.
In this work, we present a Dirac-type model of four-dimensional (4D) Z2 topological insulator (TI)
protected by CP-symmetry, whose 3D boundary supports an odd number of Dirac cones. A...
We report on experimental progress towards quantum gas microscopy of ultracold lithium-6 in low-noise optical lattices with tunable geometry. By overlapping a superlattice beam over a two-dimensional square lattice, our setup enables the site-resolved study of Fermi-Hubbard physics in triangular, hexagonal, dimerized and quasi-1D geometries. Such nonstandard bandstructures are believed to host...
We present a new approach to search for hadronic CP violation by measuring the $^{223}$Fr nuclear Schiff moment in ultracold assembled FrAg (francium silver) molecules. The $^{223}$Fr nucleus is known to have octupole deformation that leads to a factor of ~300 enhancement in the size of its Schiff moment for a given strength of CP-violating hadronic interactions [1]. The observable...
Ultracold quantum gases of atoms or molecules have become an outstanding tool to create and study various quantum many-body systems. Thanks to their high degree of controllability, they can be considered as quantum simulators - special purpose analog quantum computers - to address specific problems. An important example is optical lattice systems, which enable the implementation of the Hubbard...
Two-photon transitions in neutral atoms are attractive candidates for the development of compact and portable optical clocks. Such clocks can be used to search for dark matter and dark energy, to build a gravitational wave telescope, to perform ultra-precise surveys of the earth's gravitational potential, and to serve as the foundation for the new definition of the SI second. The Doppler- and...
Quantum degenerate gases of ultracold dipolar molecules present a promising platform for advances in quantum simulation, quantum chemistry, and searches for physics beyond the Standard Model. Direct laser cooling of dipolar molecules is one successful method for achieving ultracold temperatures. Currently, we use sub-Doppler $\Lambda$-enhanced gray molasses cooling to load SrF molecules into...
Trapping cold neutral atoms in close proximity to nanostructures has raised a large interest in recent years, pushing the frontiers of cavity-QED and boosting the emergence of the waveguide-QED field of research. Such platforms interfacing trapped cold atoms and guided light in nanoscale waveguides are a promising route to achieve a regime of strong coupling between light and atoms [1].
In...
Recent cold atom experiments have observed bad and strange metal behaviors in strongly-interacting Fermi-Hubbard systems. Motivated by these results, we calculate the thermoelectric transport properties of a 2D Fermi-Hubbard system in the weak coupling limit using quantum kinetic theory. We find that many features attributed to strong correlations are also found at weak coupling. In...
How much time does a tunneling particle spend in a barrier? A Larmor clock, one proposal to answer this question, measures the interaction between the particle and the barrier region using the spin degree of freedom of the particle to clock the dwell time inside the barrier. We report on precise Larmor time measurements of a Bose-Einstein condensate of 87Rb atoms tunneling through an optical...
Resonantly enhanced and controllable p-wave interactions in ultracold atomic systems are a promising test bed for realizing unconventional superconductors and superfluids with non-trivial transport properties. However, p-wave and other antisymmetric interactions are weak in naturally occurring systems, and their enhancement via the Feshbach mechanism has been limited by three-body loss. ...
Increasingly precise measurements of the permanent electric dipole moment of the electron (eEDM) probe physics beyond the standard model and shed light on open questions such as the baryon asymmetry and dark matter. Our measurement of the eEDM uses a thermal cloud of HfF+ ions held in an RF trap, allowing us to leverage second-scale coherence times and the large internal electric fields...
We report a microwave assisted optical vector magnetometer. Our method is based on the frequency difference and relative amplitudes of microwave-optical double resonances for different magnetic dipole transitions. Two hyperfine levels of $^{87}{\rm Rb}$ ground state are coupled strongly by a microwave field inside a cylindrical microwave cavity. A strong pump beam connects F = 2 [ground state]...
Turbulence is a multi-scale phenomenon, found in systems ranging from non-linear optics to the dynamics of the early universe. While turbulence escapes a complete microscopic understanding it is commonly associated with cascades, transporting system-specific conserved quantities, across different length scales.
Here, we employ a two-dimensional and homogenous ultracold Bose gas – a system...
Many sectors of society and the economy are now heavily reliant on Global Navigation Satellite Systems (GNSS). However, GNSS has several intrinsic vulnerabilities and cannot be used underwater or underground. In these situations, Inertial Navigation Systems (INSs) can act as a reliable alternative. These self-contained devices reconstruct the trajectory of a vehicle being tracked by measuring...
Scalable ultracold Rydberg atom arrays provide an intriguing platform for programmable quantum computation. We present a new system for a 2D Rydberg qubit array of 87Rb atoms embedded in a low-vibration cryostat. Cryopumping will improve the atom vacuum lifetime to fully leverage the scalability of Rydberg platforms, and a 30 K environment will extend the Rydberg lifetime to several times its...
Optical-tweezer arrays are a powerful platform for realising analog and digital quantum simulators. However, they share the scalability problem common to all quantum hardware. Here, we present a new experimental setup that integrates the tweezer technology in a cryogenic environment. At 4K, we are able to measure a vacuum-limited lifetime of more than 6000 seconds, which represents a...
Quantum gas microscopes are a powerful tool which can be used study particles confined to an optical lattice. By fluorescing trapped particles under an objective with a high numerical aperture it is possible to obtain single site resolution of the optical lattice. This has already been demonstrated with atoms and has paved the way for a novel platform for simulation experiments for lattice...
Optical lattice clocks have demonstrated fractional uncertainty and instability at the $10^{-18}$ level and beyond. At this performance level, such systems become useful for applications including tests of general relativity, searches for dark matter, time-resolved measurements of geophysical phenomena such as Earth tides, and remote comparisons between distant metrological institutes....
Accurate atomic data is considered to be the principal way to effectively solve the future energy problem as a clean and infinite energy resource and it is being developed internationally via the International Thermonuclear Experimental Reactor $(ITER)$ Project [1]. Then, extensive spectroscopic studies both experimental and theoretical have been performed in the last few years in order to...
Searches limiting the value of the permanent electric dipole moment on the electron (eEDM) are a sensitive probe of the Standard Model of particle physics and its extensions. Such searches have been performed in a number of different atoms and molecules, which resulted in the best current limit on the eEDM of $|d_e| < 1.1 \times 10^{-29}~\rm{e~cm}$ [1]. Our experiment has been setup with a...
$^{171}$Yb$^+$ ions feature two optical clock transitions: an electric quadrupole (E2) transition at 436 nm and an electric octupole (E3) transition at 467 nm. These two transitions have very different properties due to the different electronic structure of their excited states. In particular, they have a large differential sensitivity to the fine structure constant α, so that tight limits on...
We aim to develop a new kind of electromagnetic field sensor by combining the high metrological performance accessible thanks to the exaggerated Rydberg states properties with the high degree of control and tunability offered by cold atomic ensembles trapped in arrays of optical tweezers. We plan to probe EM-fields over a wide frequency range from few 100s of MHz to few THz, given by the...
In a cold-atom experiment with an optical tweezers array, a laser beam with a designed wavefront is focused through a high numerical-aperture objective lens to form an arbitrarily shaped light pattern on the focal plane in a vacuum chamber [1, 2, 3]. Accordingly, the pattern is often deteriorated by aberrations in optical components and thereby should be monitored and evaluated in situ....
Information inference from noisy systems is a focus of interest of various research and engineering disciplines. In 1960, Rudolf E. Kalman published a paper on an optimal filtering technique for systems described by linear dynamics and measurement models whose noise statistics is Gaussian [1]. In particular, this so-called Kalman Filter constitutes a way to construct an estimator that allows...
The Florida State University cryogenic Penning ion trap has previously produced the most precise values of the masses of heavier atoms required for several important atomic physics applications [1]. These include Rb and Cs for atom-interferometric measurement of h/m for the fine structure constant, and isotopes of Sr and Yb for King plot analyses. More recently we have focused on mass ratios...
A fair number of atomic sensors require a homogeneous B-field for long-lasting Larmor oscillation of atoms. On the other hand, various electronics used in the experients emit magnetic fields, destroying the homogeneity of the deliberately homogeneous B-field. We demonstrate a DBR laser-TEC packaging and a heater which self-cancel their emitted B-field by antiparallel current configurations....
The EDMcubed collaboration is working towards a measurement of the electric dipole moment of the electron (eEDM) using barium-monofluoride (BaF) embedded in an argon solid. The large numbers of embedded BaF in this measurement scheme [1] gives the potential for a very precise eEDM measurement. In this work, we present precise relativistic electronic structure calculations (all-electron, with...
We propose a scalable, modular, fault-tolerant architecture for quantum computing based on Rydberg arrays and Rydberg compatible optical cavities. While previous modular architectures have focused on very small modules containing 2-5 qubits, our architecture consists of large modules containing thousands of physical qubits, which form surface code patches that are linked together by optical...
The fate of topological transport in the strongly correlated regime raises fundamental questions on the role of geometry in quantum many-body physics. A paradigm of quantised transport is the topological Thouless pump, which represents the one-dimensional, dynamic analogue of the quantum Hall effect. A few experiments have explored the effects of interactions on Thouless pumping in two-body...
The collective absorption and emission of light by an ensemble of atoms is at the heart of many fundamental quantum optical effects and the basis for numerous applications. However, beyond weak excitation, both experiment and theory become increasingly challenging. Here, we explore the regimes from weak excitation to inversion with ensembles of up to one thousand atoms that are trapped and...
The investigation of propagation of pulses in optically dressed media is one of the most basic problems in optics. I will analyze a new superluminal propagation regime in the ladder-type three-level systems near a two-photon resonance where an anomalous dispersion appears accompanied by a small absorption. These conditions are necessary to achieve group velocities greater than the speed of...
We are realizing a new experiment for investigating and controlling ultracold chemical reactions. We plan to use mixtures of magnetic atoms and create molecular gases and atom-molecule mixtures with widely tunable interactions. Combining techniques from quantum optics and physical chemistry, we will develop new methods for shielding chemical reactions and stabilizing bosonic molecular gases.
Dicke superradiance is a phenomenon where atoms at an identical location synchronize and collectively emit photons in a short, bright burst. We investigate the many-body decay of an extended array of atoms coupled to a one-dimensional optical channel. We show that Dicke superradiance in waveguides is intrinsically different from superradiance in cavities and free space, as there are two...
Fermionic quantum systems with a tuneable atom number have proven to be a viable platform for exploring the emergence of many-body phenomena. In our experimental setup we can deterministically prepare few-body fermionic quantum systems in a two-dimensional harmonic potential with stable closed-shell configurations.
Using a time-of-flight expansion in combination with our imaging technique,...
Interactions form the basis for the experimental generation of entanglement between quantum objects. Using all-to-all interactions, numerous experiments with atomic ensembles have generated quantum states which provide a higher precision in sensing protocols compared to unentangled states. However, many envisioned applications in quantum sensing and computation require greater control over the...
Quantum entanglement has attracted much attention in the study of quantum many-body systems because it plays important roles in various phenomena such as thermalization of isolated quantum systems. Especially, it is remarkable that the 2nd-order Renyi entropy (RE), which is a measure of entanglement, has been successfully measured in the system of bosons trapped in a 1D optical lattice....
We investigate the driven-dissipative dynamics of 1D arrays of multilevel atoms interacting via photon mediated dipole-dipole interactions and trapped at subwavelength scales. In contrast to two-level atoms, we show that multilevel atoms in the low excitation (weak drive) regime can become strongly entangled. The entanglement arises from the action of a non-trivial effective Hamiltonian and...
We experimentally investigate the entanglement of two spatially separated many particle systems. Our experiments are based on a two component pseudo spin-$1/2$ Bose Einstein condensate of $^{87}$Rb on an atom chip. By engineering the interatomic interactions through state dependent trapping we are able to produce entangled spin-squeezed states in this system. Using coherent spin manipulations...
Cold Atom-based technology promises a new generation of navigation systems potentially suitable for Global Navigation Satellite System-denied environments. However, despite the promise of superior inertial navigation capabilities, a correct identification and quantification of the errors must be carried out to assess what and how system parameters affect the sensor performance. In this...
We propose and demonstrate a scalable scheme for the simultaneous determination of internal and motional states in trapped ions with single-site resolution. The scheme is applied to the study of polaritonic excitations in the Jaynes-Cummings-Hubbard model with trapped ions, in which the internal and motional states of the ions are strongly correlated. We observe quantum phase crossovers of...
The wide-ranging scientific applications of ultracold molecules have inspired significant efforts in cooling and controlling molecules in the single quantum state level. Many potential applications are still hampered by the finite temperatures experimentally achieved. As temperatures are reduced further, motional decoherence rates are suppressed and fidelities increase, opening new...
An interacting two-dimensional (2D) Bose gas becomes superfluid below a critical temperature through the BKT mechanism. In this phase, under hydrodynamic conditions where collisions keep the gas in local thermodynamic equilibrium, Landau's two-fluid model predicts the existence of two distinct sound-like excitations. These, so-called first and second sounds, have recently been observed in 2D...
Initially considered in the context of solid helium, the exotic supersolid phase is characterized by the spontaneous breaking of gauge and spatial translation symmetries. This implies acquiring the phase coherence of a superfluid and the crystalline structure of a solid. The long-sought regime has been recently observed for cavity-coupled atomic systems [1], dipolar gases [2-4] and spin-orbit...
The study of collective excitations in superfluids systems has been an active and important research topic since the very beginning of the exploration of quantum fluids. Their study offers the possibility of probing several important properties of these systems, such as the spectrum of excitations, or the equation of state.
Here we present our work on the observation and study of Faraday...
The most challenging problems from materials science and quantum chemistry involve strongly correlated states of mobile fermions. Mapping such itinerant systems to effective spin-1/2 systems realized on most quantum computing prototypes comes with a large computational overhead. New types of quantum processors based on inherently fermionic computation are therefore needed.
FermiQP will...
Spin-polarized Fermi gases in low dimensions offer a pathway to the quantum simulation of matter. Through a Feshbach mechanism the p-wave ($L=1$) interactions governing these systems, which are suppressed by a centrifugal barrier at low energy, may be tuned and enhanced by a magnetic field. In doing so one may realize phenomena as diverse as chiral superfluidity in two dimensions to...
Heat rectification, firstly observed in 1936 by Starr [1], is the physical phenomenon, analogous to electrical current rectification in diodes, in which heat current through a device or medium is not symmetric with respect to the exchange of the baths at the boundaries. In the limiting case the device allows heat to propagate in one direction from the hot to the cold bath while it behaves as a...
When a single photon traverses a cloud of 2-level atoms on resonance, how much time does it spend as an atomic excitation, as measured by weakly probing the atoms? It turns out that the answer, on average, is simply the spontaneous lifetime, multiplied by the probability of the photon being scattered into a side mode. It is tempting to infer from this that photons that are scattered spend, on...
The Air Force Research Laboratory (AFRL) has been developing atom chips for use with cold-atom sensing and atom interferometry. We detail numerous advances in processing and fabrication techniques. Design improvements support tighter traps and rapid prototyping. Development of vias allow atom chips to serve as vacuum-chamber walls, decreasing current demands. Fabrication innovations that...
With the evergrowing interest in quantum cooperativity, comes an ongoing
effort to study light-induced correlations in atomic media. In
these typically extreme dense regimes, with atomic distances below
the scattering lights wavelength, a direct matter-matter coupling is introduced
by electric and magnetic interactions. We intend to study
light-matter interactions in dense dipolar media...
Exact solutions for quantum many-body systems are rare, but provide valuable insights for the description of universal phenomena. Recently, specific solutions of the Bethe ansatz equations for 1D anisotropic Heisenberg models were found that can carry macroscopic momentum yet no energy on top of the ferromagnetically ordered "vacuum" state, dubbed phantom Bethe states. As a consequence of...
We consider computer generated configurations of quantized vortices in planar superfluid Bose–Einstein condensates. We show that unsupervised machine learning technology can successfully be used for classifying such vortex configurations to identify prominent vortex phases of matter [1]. The machine learning approach could thus be applied for automatically classifying large data sets of vortex...
We present a microscopic theory of thermally-damped vortex motion in oblate atomic superfluids that accounts for previously neglected number-conserving interactions between superfluid and thermal atoms. This mechanism causes dissipation of vortex energy due to mutual friction, as well as Brownian motion of vortices due to thermal fluctuations. We present an analytic expression for the...
Negative absolute temperature entails a situation where the entropy of a system reduces as the internal energy increases. As the idea was put forward by N. Ramsey in the 1950s [1], the concept of negative absolute temperature has been actively discussed, and has led to the eventual observation with cold atoms in a square lattice [2]. In this poster, we describe our experiment with K(39) atoms...
The matter-antimatter asymmetry of the universe suggests that new sources of time-reversal symmetry (T) violation lurk at energy scales beyond the reach of colliders. New particles or T-violating interactions coupled to nucleons can lead to nuclear Schiff moments or magnetic quadrupole moments, which result in measurable energy differences between the spin states of nuclei inside electrically...
Pairing is the fundamental requirement for fermionic superfluidity and superconductivity. To understand the mechanism behind pair formation is an ongoing challenge in the study of many strongly correlated fermionic systems.
On this poster, I present the direct observation of Cooper pairs in our experiment. We have implemented a fluorescence imaging technique that allows us to extract the full...
Since the 90's, many laboratories have developed atom interferometers to sense accelerations and rotations [1]. For many applications, small compact devices are desirable, and the atom chip [2] appears to offer a path towards miniaturization. Moreover, performing the interferometry sequence on-chip with trapped atoms decouples the sensitivity of the sensor from its size, allowing in principle,...
The complex structure of polyatomic molecules offers powerful features that can be exploited for applications in quantum simulation and precision measurement. One of these features is a plethora of ro-vibrational states. In the linear triatomic molecule SrOH, two vibrational states have a near-degeneracy that can be probed with microwaves (in contrast to typical vibrational splittings of...
Ultracold dipolar molecules are a promising system for interesting research in ultracold chemistry, novel interactions in quantum gases, precision measurements or quantum information.
Here we report on photoassociation spectroscpoy in an ultracold mixture of Yb and Rb near the $^1S_0 \rightarrow {}^3P_1$ intercombination line of Yb at 556 nm. While in previous work we have identified...
In cold and ultracold mixtures of atoms and molecules, Rydberg interactions with surrounding atoms or molecules may, under certain conditions, lead to the formation of special long-range Rydberg molecules [1, 2, 3]. These exotic molecules provide an excellent toolkit for manipulation and control of interatomicand atom-molecule interactions, with applications in ultracold chemistry, quantum...
In cosmology, the relativistic scalar fields that cause the universe to expand are damped by Hubble friction, which is due to the dilation of the underlying spacetime metric. Here, we have simulated the Hubble friction using a toroidal Bose-Einstein condensate (BEC) of 23Na atoms, in which the phonon fields can serve as an analogy to the cosmological scalar fields. We experimentally measure...
Control over the structure of interactions is essential for developing flexible quantum protocols. We couple an array of atomic ensembles to a driven optical cavity, creating an XY model. Using a magnetic field gradient and modulating the cavity field enables us to prune the naturally all-to-all connectivity of cavity-mediated interactions. We confirm these coupling graphs by direct...
Achieving ultracold temperature of neutral diatomic molecules is one of the pre-requested key steps for using them as a quantum platform. Owing to molecules' abundant internal structures and large electric dipole moments, a long coherence time and a long-range interaction could be achieved when we make an array of diatomic molecules trapped in optical tweezers.
To make an ultracold...
Ultracold molecules are a powerful platform for metrology, precision measurements and searches for new, beyond-the-Standard-Model physics. In particular, Sr$_2$, thanks to its simple structure, insensitivity to external fields and narrow optical transitions, provides an excellent testbed for the search for new interactions. Here, we present a detailed characterisation of our $^{88}$Sr$_2$...
Caustics are singularities arising from natural focusing and are well known in optics but also occur in any system that has waves including quantum waves. Caustics take on universal shapes that are described by catastrophe theory and dominate interference patterns in the semiclassical regime.
My group has been extending these ideas to quantum fields, such as those found in the sine-Gordon and...
Sub-wavelength arrays of atoms have been shown to have remarkable optical properties, like near perfect reflection and low diffraction loss. However, the collective effects resulting in these properties also serve to wash out the otherwise strong underlying nonlinearity of the atoms, rendering the arrays largely linear. We have found that by putting together two arrays we can recover a strong...
Realizing quantum speedup for solving practically relevant, computationally hard problems is a central challenge in quantum information science. Using Rydberg atom arrays composed of up to 289 coupled qubits in two spatial dimensions, we experimentally investigate quantum optimization algorithms for solving the Maximum Independent Set problem. We use a hardware-efficient encoding associated...
Plasmonic lattices of metal nanoparticles have emerged as an effective platform for strong light-matter coupling, lasing, and Bose-Einstein condensation. However, the full potential of complex unit cell structures has not been ex- ploited. On the other hand, bound states in continuum (BICs) have attracted attention, as they provide topologically protected optical modes with diverging quality...
Lasing in the superradiant or “bad cavity” regime has attracted interest in the optical clock community as it offers an alternative to conventional lasers limited by the thermal noise fluctuations of reference cavities. In our experiment, we investigate pulsed lasing on the 7.5 kHz clock transition of $^{88}$Sr atoms in an optical cavity. We continuously repump the lasing to achieve pulse...
In this poster we present the realization of ferromagnets (FM) and antiferromagnets (AFM) for square arrays up to 100 atoms realizing the dipolar XY model. Our platform is based on individual atoms of rubidium trapped in arrays of optical tweezers. We encode the effective spin on two Rydberg states. The coupling between the spins results from the resonant dipole-dipole interaction, varying as...
Cold Rydberg atoms have recently become a promising platform for quantum information processing and quantum simulations due to their specific properties. The Rydberg blockade regime allows us to entangle qubits and to make CNOT and CPhase gates. Optical nanofibers (ONFs) are an excellent tool to interact with such atoms. They are relatively easy to install into experimental setups because of...
Rydberg Atoms in highly excited electronic states with n=30-200 can be excited within Bose-Einstein condensates (BECs), and while lifetimes are shorter than in vacuum [1,2], these atoms live long enough to cause a response of the BEC mean field [3]. During this, thousands of ground-state atoms are present within the Rydberg orbit, allowing the study of atoms moving within atoms [4].
We...
We present experimental work performed in a cryogenic apparatus exploiting a segmented ion trap architecture for the implementation of quantum algorithms [1]. The quantum register consists of a linear string of 40Ca+ ions which are individually controlled by tightly focused laser beams perpendicular to the crystal axis. Light is delivered by a waveguide array allowing to individually feed each...
Point-source atom interferometry (PSI) offers a pathway for realizing compact inertial sensors with relatively low experimental complexity. Rotation sensing in PSI gyroscopes uses the velocity distribution in an expanding cold-atomic cloud to realize many parallel atom interferometers with velocity-dependent phase shifts. The scale factor relating the rotation rate to the observed atomic...
Atom interferometry as a tool for precision measurements opens up a broad field of application: from testing fundamental physics to geodesy or navigation. Since the sensitivity of an atom interferometer scales quadratically with the interrogation time, operating on a microgravity platform is highly beneficial. Extended times of flight of several seconds require low expansion rates of the...
The radiative properties of ions (Z= 2-53) belonging to the helium isoelectronic sequence are reported. Energy levels for the ground state and the lowest 1s2l singly excited states are considered. The effects of correlation effects are studied for the selected ions by increasing the active set (AS). Relativistic effects such as the Breit interaction and the QED corrections are also computed....
This work reports on the observation of superradiance decoherence caused by long-range dipole-dipole interactions between Rydberg atoms. A cold atom cloud is prepared in the mode volume of a weakly driven optical cavity, and excited to a Rydberg state. The cavity transmission monitors the Rydberg dynamics in real-time and detects superradiant enhancement of the transition rates between...
Raman interactions are a powerful tool for performing arbitrary rotations between two Zeeman levels of an individual ion or a neutral atom. Universality of the technique places it in a central role in many quantum technologies: single qubit gates in atomic quantum processors, mediating interactions in quantum simulators, and mapping quantum information into long-lived states in optical quantum...
Combining cold Rydberg atoms with an optical nanofiber (ONF) apparatus provides a platform for both investigating the generation and manipulation of Rydberg atoms, but also an ideal way for generating a 1D chains of Rydberg atoms using the strong interactions of atom-ONF hybrid systems combined with the ability to trap atoms at the surface of the fiber in a 1D chain.
The evanescent field...
Optical tweezer arrays of neutral atoms provide a controllable and scalable platform for quantum computing and quantum simulation. Neutral atoms in these arrays interact via long-range van der Waals interactions, when excited into Rydberg states. A dual species array adds to the toolbox of atom arrays and allow for schemes involving multiple species. For example, non-destructive measurement, a...
Nuclear Schiff moments (NSMs) present a powerful probe into new physics through their connection to CP-symmetry violation. We are investigating the application of molecular matrix methods to NSM searches of radioactive isotopes, particularly radium-225, which has an enhanced Schiff moment resulting from its octupole deformations. These methods involve trapping polar molecules in a noble gas...
Ultracold dipolar molecules offer an ideal platform for investigations in the fields of quantum simulation, precision measurement and quantum chemistry. The range of possibilities offered by ultracold molecules could be substantially extended by employing the previously unexplored class of open-shell molecules like RbSr. Thanks to its unpaired valence electron RbSr possesses both a magnetic...
Robust and accurate tracking of acceleration remains a challenging problem in many fields. For geodesy, geophysics or underground exploration, precise mapping of gravity requires the use of onboard gravimeters or gradiometers as well as inertial navigation systems to compute accurate positioning information from classical accelerometers and gyroscopes. Quantum sensors based on cold-atom...
State preparation often suffers from various sources of device-dependant noise. It is hard to characterise and let alone mitigate the noise. Machine learning can be used to automate the denoising task. Quantum computers are the ultimate machines to process quantum signals. As such, we propose to use machine learning on quantum computers to denoise quantum data.
For this, we design a...
Strontium optical lattice clocks (OLC) are a promising instrument for applications ranging from the redefinition of the second in the international system to geodesy and fundamental physics, for instance, dark matter detection, variation of fundamental constants, or general relativity tests. LNE-SYRTE, Observatoire de Paris operates two Sr OLCs with a systematic uncertainty on the order of...
We theoretically investigate interatomic interactions and ultracold collisions between chromium and lithium atoms. We use the coupled cluster and multireference configuration interaction methods to calculate the potential energy curves and the permanent and transition electric dipole moments for the quartet, sextet, and octet electronic states of the LiCr molecule correlated to the four lowest...
After laboratory optical atomic clocks have reached fractional frequency uncertainties in the 10$^{-18}$ regime, it is an ongoing task to miniaturize these complex clocks and make them transportable and in-field deployable, without compromising their performance. This effort is primarily motivated by promising prospects in geodesy. Together with accurate frequency transfer via fiber links,...
Optical forces on atoms derive from the momentum exchange between the atoms and an incident light field [1]. Atoms cannot absorb the linear momentum of light into their internal coordinates the same way as energy ($\hbar \omega_{\ell}$) and angular momentum ($\Delta \ell = \pm 1$), so absorption or emission must involve atomic motion, usually in the form of a recoil momentum $\Delta p \equiv...
Atom interferometry is based on the measurement of phase differences in coherent matter waves. As such, it is an ideal technique for measuring inertial forces caused by e.g. acceleration and rotation. The precision of the measurements is provided by the standing light wave imprinting its position-dependent phase onto the matter waves and therefore acting as a fine-spaced ruler.
Being based...
Rydberg quantum optics allows to create strong optical nonlinearities at the level of individual photons by mapping the strong dipolar interactions between collective Rydberg excitations onto optical photons. The interactions lead to a blockade effect such that an optical medium smaller than the blockaded volume only supports a single excitation which is collectively shared amongst all...
Polyatomic molecules can provide improvement over diatomic systems in cold chemistry, precision measurement of fundamental physics, and quantum information. Slowing these species to trappable velocities is a major limitation in realizing these applications. Over the past decade, radiative slowing methods have been successfully applied to diatomic and, recently, triatomic molecules with highly...
We use photoassociation of spin polarized ($F=3$, $m_f=3$), ultracold cesium atoms confined in a 1D optical lattice to confirm the existence of the two lowest lying vibrational levels in the $0^-_g$ pure long-range molecular potential of Cs$_2$. The observation of these two levels confirms the theoretical predictions of Bouloufa et al. [1] postulating that the numbering of vibrational levels...
We have shown that two-channel Feshbach theory works well to describe p-wave Feshbach resonances [1], however a peculiar result of a non-intuitive molecular magnetic moment led to the realization that an additional shape resonance was part of the scattering problem and unaccounted for.
We study how two shape resonances in separate hyperfine channels in Potassium-40 interact with a Feshbach...
Atom interferometers are sensitive to the signatures of gravitational waves, ultra-light dark matter and other fundamental physics phenomena. The development of this new class of quantum detector will complement traditional detection methods and extend measurement capabilities.
The Atom Interferometer Observatory and Network (AION) [1] is a planned series of atom interferometers operating...
A matter-wave Fabry-Perot (FP) for the generation of ultracold wavepackets could be implemented using an optical double barrier. Observation of the transmission spectrum of a single such FP becomes impractical for wavepacket temperatures above about 100pK. The resonances are washed out due to the velocity width of the incident wavepacket being larger than the width of the resonances. We...
The large asymmetry between matter and antimatter in the Universe is a mystery. The formation of this extra matter requires charge parity (CP) violation beyond that contained in the standard model, and therefore points towards new physics [1]. The electron’s electric dipole moment (eEDM) is sensitive to this new physics. Precision measurement of the eEDM tests physics beyond the Standard Model...
The old problem of the discrete spectrum of the hydrogen atom obeys a SO(4) symmetry, which is isomorphous to two subgroups that obey the algebra of angular momentum. The algebraic structure allows us to formulate a basis closely related to the properties of the wave function in parabolic coordinates. On the other hand, the properties of other angular momenta, such as electron spin and nucleus...
Discrete time crystals created in a Bose-Einstein condensate (BEC) bouncing resonantly on a periodically driven atom mirror can involve dramatic breaking of discrete time translation symmetry [1] with response periods up to s 100 times the driving period T [2]. This allows the creation of big time crystals having a large number of temporal lattice sites. By choosing suitable Fourier...
Quantum phase transitions occur at temperatures close to absolute zero and are driven by quantum fluctuations. One paradigmatic example is the change from a superfluid to a Mott insulator of ultracold bosons. This transition typically is continuous, i.e., the system undergoes a smooth change.
Using a resonantly shaken lattice, we could however turn the Mott transition into a discontinuous...
There has been a long-term effort in reducing inelastic losses in quantum gases, from dipolar relaxation in spin mixtures to reactive collisions in molecules. For the first time we show shielding between atoms via the dipolar interaction and strong confinement. This has been achieved with bosonic dysprosium and resulted in an order of magnitude suppression of dipolar relaxation. Theoretical...
The interplay of pairing with density wave order is one of the most prominent feature of strongly correlated electronics systems, such as high temperature superconductors. We have realized a Fermi gas with short and long range interactions, independently and simultaneously controllable. Starting from a quantum degenerate, unitary Fermi in a cavity [1-4], we pump the system from the side in the...
In quantum information and computation, very high fidelity of gate operations is required. Measuring tiny gate errors with high accuracy is a difficult task, which is traditionally done by randomized benchmarking.
In this work we present a new method which allows to determine the gate errors of Raman qubits, in which the qubit states are coupled in a Raman transition via another state,...
Using laser pulses to manipulate the internal quantum states of atoms and molecules provides new opportunities to create novel quantum devices. Coherent population transfer is the fundamental tool for many potential quantum applications such as atomic lithography, Rydberg arrays, and quantum information processing. We describe the Rydberg state excitation in a three-level system through...
The state-of-the-art optical atomic clocks rely on trapping, cooling and readout at the same point in space and the cooling stages are separated in time; however, they suffer from finite dead-time between measurements leading to additional noise, and complicated control sequences. The next generation of optical clocks should be continuous with inherently zero dead-time and steady-state...
Dipolar molecules in two dimensions are a powerful platform for the study of quantum many-body physics, thanks to their long-range, anisotropic dipolar interactions. We have developed key experimental capabilities required for the study of such systems, including layer-resolved state control and detection, field-tunable dipole orientation and strength, and control of both intralayer and...
Quantum gas microscopes have become a major element for quantum simulations using ultra-cold atoms in optical lattices. They are for example used to observe long-range order such as anti-ferromagnetic correlations in far field optical lattices using density and spin resolved microscopy. Decreasing the period of such lattice offer interesting perspective to increase atom-atom interaction...
Density-matrix simulations of an optical scheme for producing a large optical force on barium-monofluoride (BaF) molecules are presented. The scheme uses short laser pulses to induce excitation to the A Pi 1/2 state, with pulses from counter-propagating laser beams causing stimulated emission back to the ground electronic state. A magnetic field is used to remove degeneracies to avoid dark...
We investigate the physics of Dicke superradiance with multilevel atoms. Dicke superradiance is a dissipative many-body phenomenon where excited atoms collectively emit a short and intense burst of light. While this physics is well understood for two-level systems in a cavity, our work involves extended arrays of multilevel atoms in free space. In previous work, we showed that Dicke...
1. Introduction
To convert a femtosecond laser into a frequency-comb laser, it is frequently essential to use a costly atomic clock [1] to stabilize the repetition rate (f rep) and sophisticated nonlinear optics to lock the offset frequency (f ceo). In this report, we demonstrate that the mode frequencies of a comb laser can be directly referenced to two stepwise two-photon transitions...
"Ultracold molecules are poised to open many important applications, ranging from quantum information science to precision tests of fundamental physics. In the past decade, direct laser cooling of molecules has successfully achieved magneto-optical trapping, sub-Doppler cooling, and confinement in conservative optical traps. A key research direction for molecule-based quantum science requires...
We report realizations of various dynamical hybrid light-matter phases, as a discrete dissipative time crystal [1], dynamical bond density wave phase [2-4], and limit cycle phase [5], by strongly coupling an atomic quantum gas to the light field of an optical cavity. The key feature of the cavity is a very small field decay rate ($\kappa / 2\pi$ = 3.6kHz), which is in an order of the recoil...
Improved searches for the electron electric dipole moment (eEDM) require large numbers of polar molecules with long spin coherence times. We report trapping of BaF molecules in cryogenic neon ice, with trap lifetimes exceeding two weeks. Laser-induced fluorescence measurements indicate that the molecules are only weakly perturbed compared to previous studies on atoms in inert solids. Our...
The optical properties of a fixed atom are exquisitely well-known and investigated. For example, one important phenomenon is that the atom can have an extraordinarily strong response to a resonant photon, as characterized by a resonant elastic scattering cross section given by the wavelength of the transition itself, $\sigma_{sc}\propto\lambda^2$. The case of a tightly trapped ion, where the...
Polar symmetric top molecules offer a multitude of interesting research opportunities as their permanent electric dipole moment makes them interact strongly and anisotropically and allows manipulating them already with moderate static electric fields. This, together with their wealth of internal states, permits studies and applications ranging from cold dipolar collisions to quantum...
Realization of strongly interacting particles under the presence of a magnetic field can lead to novel phases of matter with topological order. Here, we demonstrate adiabatic preparation of the ground state of a two-particle Harper-Hofstadter system under different fluxes with ultracold bosonic 87Rb atoms in an optical lattice. A superimposed running lattice of two Raman beams and a magnetic...
Encoding quantum information in a harmonic oscillator offers a resource efficient method for quantum error correction, compared to the use of multiple two-level systems. The Gottesman-Kitaev-Preskill (GKP) encoding [1] is particularly promising and has recently been realized in both trapped ions [2, 3] and superconducting microwave cavities [4].
State preparation, readout, single qubit...
The past decade has seen astounding progress in the field of digital quantum computation (QC). Traditionally, QC circuits consist of a set of coherent qubit operations, quantum gates, that are by definition unitary and therefore reversible. Parallel to the familiar use of quantum gates, a new paradigm of quantum information theory is emerging in which hybrid quantum-classic algorithms are...
Trapped-ion systems are amongst the most promising approaches for realizing useful quantum computers and simulators. However, scaling up the qubit register size without compromising performance remains challenging. In the experimental setup presented here we work on realizing large registers of trapped barium-ion qubits.
Barium-ion qubits offer several features favourable for quantum...
Topological quantum states are associated with integer invariants and are thus protected from continuous small deformations of the system. Topological invariants ensure the robustness of various phenomena, e.g. the quantized Hall conductance in two-dimensional electron gases subjected to a magnetic field, and are promising tools in different fields of physics, such as quantum computation....
Topological phases with broken time-reversal symmetry and Chern number |C|>=2 are of fundamental interest, but it remains unclear how to engineer the desired topological Hamiltonian within the paradigm of spin-orbit-coupled particles hopping only between nearest neighbours of a static lattice. We show that phases with higher Chern number arise when the spin-orbit coupling satisfies a...
We have undertaken a series of measurements of atomic properties of group III and IV systems to test ongoing ab initio atomic structure calculations. These multi-valence systems have relevance to tests of symmetry violation and other fundamental physics searches. Prior work involved measurements of polarizability, isotope shifts, and hyperfine structure in various excited states of the...
We investigate the scattering of a high-spin spherical atom Cr ($^7$S) with a closed shell atom Yb ($^1$S). We evaluate the spin-spin interaction arising from the multiple unpaired electrons from the Cr atom perturbed by the Yb atom, and show this provides a substantial coupling. We perform calculations of the magnetic Feshbach resonances this causes, and show are guaranteed to exist at low...
We propose a theoretical scheme to study the Lee-Huang-Yang (LHY) quantum correction on the interference of two expanding Bose-Einstein condensates (BEC). The key is to consider a long-term expanding condensate whose wave function mimics the dynamic Gaussian wave. This enables to solve analytically the wave function at an earlier time when the LHY correction is active. Based on the GPE...
Vertical external-cavity surface-emitting lasers (VECSELs) augmented by intracavity nonlinear optical frequency conversion have emerged as an attractive light source of ultraviolet to visible light for demanding scientific applications, relative to other laser technologies. They offer high power, low phase noise, wide frequency tunability, and excellent beam quality
in a simple and...
Macroscopic mechanical devices in the quantum regime can play a key role in quantum communication, quantum sensing and fundamental tests of quantum mechanics. We use a fiber cavity filled with superfluid $^4$He of mass ~ 1 ng as our mechanical resonator. Leveraging single photon counting techniques, we manipulate and probe the motional state of a superfluid $^4$He resonator. The arrival times...
Precision experiments in the hydrogen atom have a long tradition and extensive studies of transitions between low lying $n\leq12$ states were carried out [1-6]. These measurements can be used to determine values of the Rydberg constant and the proton charge radius. We present a new experimental approach to perform measurements of transition frequencies between the metastable 2s $^{2}$S$_{1/2}...
The quantification of topological invariants for tight-binding Hamiltonians with certain crystalline point group symmetries is well-studied, and in particular, the Chern number can be expressed in terms of the eigenvalues of the symmetry operator at the high-symmetry points of the Brillouin zone [1]. In recent years, it has become possible to utilize this relation in cold atom experiments to...
The n=2 triplet P fine structure of atomic helium is being measured using microwave transitions.
The method [1] of Frequency-Offset Separated Oscillatory Fields (FOSOF) is used to perform
the measurements. The measurement of the J=1-to-J=2 interval has been completed [2], with a
measurement uncertainty of only 25 Hz. The measurement of the 29.6-GHz J=0-to-J=1 interval
is now being...
Inertial sensors based on matter-wave interference show great potential for navigation, geodesy, or fundamental physics. Similar to the Sagnac effect, their sensitivity to rotations increases with the space-time area enclosed by the interferometer. In the case of light interferometers, the latter can be enlarged by forming multiple fibre loops. However, the equivalent for matter-wave...
NASA’s Cold Atom Laboratory (CAL) was launched to the International Space Station in 2018, where it has been conducting quantum experiments in microgravity ever since. CAL is a multi-user instrument designed to be fully operated remotely, with the possibility of astronaut-led hardware upgrades and replacements. Scientists have performed investigations ranging from BECs in bubble shaped...
Continuously monitored atomic spin-ensembles allow, in principle, for real-time sensing of external magnetic fields beyond classical limits. Within the Linear-Gaussian regime, thanks to the phenomenon of measurement-induced spin-squeezing, they attain a quantum-enhanced scaling of sensitivity both as a function of time, t, and the number of atoms involved, N. In our work, we rigorously study...
In this poster, we will present recent experiments on a quenched ferromagnetic spinor BECs. In the first part, we present the observation of spin-momentum correlated matter-wave jets from spinor BECs [1]. Preparing a quasi-two-dimensional condensate in the $m_F=0$ state, we quench the quadratic Zeeman energy to -2 kHz. Transversely propagating atomic beams in the $m_F=1$ and $m_F=-1$ state...
Time crystals are classified as discrete or continuous depending on whether they spontaneously break discrete or continuous time translation symmetry. While discrete time crystals have been extensively studied in periodically driven systems since their recent discovery, the experimental realisation of a continuous time crystal [1,2] is still pending. We report the observation of a limit cycle...
The quantum kicked rotor is a paradigm system to study classical and quantum chaos. When viewed in momentum space, it is equivalent to the Anderson model of transport in the presence of disorder, featuring dynamical localization in the synthetic momentum space. We report the observation of interaction-driven delocalization in d-dimensional (d=1-4) Anderson models in the synthetic momentum...
The search for more precise and accurate frequency standards has played a key role in the development of basic science, precision measurements and technical applications. Nowadays, optical clocks with trapped ions are achieving uncertainties in the low 10$^{-18}$ range and below. One of our group’s focuses is centered on the implementation of optical clocks with trapped $^{40}$Ca$^{+}$ and...
In the recent years, the use of nanoscale waveguides providing tight transverse confinement of light has been pushed forward in the waveguide-QED field as a mean to enhance atom-photon interactions for large number of atoms. On our experiment, we use a two-color dipole trap scheme to interface cold Cesium atoms with the evanescent field of a tapered optical nanofiber. By tuning the properties...
A magneto-optical trap (MOT) is the first step to take various atoms and molecules to the ultracold temperature. For molecules, because of their complex energy structure, there are too many parameters to be adjusted in the MOT and the preceding laser slowing stage. It is difficult to experimentally optimize all the parameters one by one. Motion simulation of particle can provide the optimized...
Driving a many-body system out of equilibrium induces phenomena such as the emergence and decay of transient states, which can manifest itself as pattern and domain formation. The understanding of these phenomena expands the scope of established thermodynamics into the out-of-equilibrium domain. We report our theoretical and experimental study on the out-of-equilibrium dynamics of a bosonic...
In order to investigate the low-energy physics of a system composed of an impurity immersed in a many-body medium, one may study the properties of the quasiparticle formed by the impurity dressed by excitations of the surrounding medium : the so-called polaron. This idea was first introduced in solid-state physics by Landau and Pekar in the 1950’s to study the coupling of electrons to a...
We observe and study a special ground state of bosons with two spin states in an optical lattice: the spin-Mott insulator, a state that consists of bound pairs that is insulating for both spin and charge transport. Because of the pairing gap created by the interaction anisotropy, it can be prepared with low entropy and can serve as a starting point for adiabatic state preparation. We find that...
We study a $p$-wave Feshbach resonance in potassium-40 with a combination of spectroscopic binding energy measurements, coupled-channels calculations, and a two-channel model [1]. Using both resonant association and spin-flip association, the binding energy of bound and quasi-bound dimers is measured across a five-gauss range. Our scattering model incorporates the ramping closed-channel state,...
The past decade has seen tremendous progress in the field of direct laser cooling and trapping of molecules, extending to new candidate platforms for quantum computing, quantum simulation, precision measurement and metrology. Here we present our progress towards laser cooling and trapping of CaH molecules. We demonstrate experimental results on transverse Sisyphus cooling of a cold beam of CaH...
The spectral separation between resonant transitions of different ion species offers mutual isolation that can be advantageous for scaling trapped ion quantum computing systems, and numerous groups are now performing experiments with mixed-species crystals of trapped ions. In our group at NIST, trapped $^9$Be$^+$ and $^{24/25}$Mg$^+$ ions in a linear RF trap have been utilized to demonstrate...
Optical parametric amplifiers are known in the literature as a tool for the generation of quantum correlated beams. Forward four-wave mixing (FWM) with gain factors on the order of 10 associated with strong intensity squeezing [1] is behind, for example, the generation of entangled fields [2].
In this work, we explore both the internal and external atomic degrees of freedom to demonstrate...
Frustrated quantum systems can host quasi-particles with fractional statistics and pose significant challenges to condensed matter theory due to their extensive ground state degeneracy. Here, we aim at quantum simulation of electronic systems on triangular lattice geometries using ultracold atoms in a quantum gas microscope.
We present the site-resolved imaging of fermionic lithium atoms in...
The degrees of freedom inherent in the structure of polyatomic molecules allow for new applications spanning the fields of quantum simulation and computation, ultracold chemistry, and precision measurements of fundamental physics. For example, the complex rovibrational structure of polyatomic molecules generically gives rise to closely-spaced levels of opposite parity that result in linear...
We report on the design and characterization of exact and heuristic algorithms to solve atom reconfiguration problems. These algorithms can be used to prepare deterministic configurations of atoms in two-dimensional arrays of optical traps, as well as to realize quantum many-body systems with dynamic connectivity graphs and time-varying interactions. We numerically quantify the operational...
Sagnac atom interferometers are a promising technique for high-performance rotation sensing, with potential applications for inertial navigation. The use of trapped atoms for the interferometer avoids the need for long free-fall distances that would be incompatible with a navigation apparatus. We have previously demonstrated a dual Sagnac interferometer using Bose-condensed atoms in a...
Quantum computation offers a revolutionary approach to how information is processed, offering new applications in material design, quantum chemistry and speed up of real-world optimisation problems, however a large number of qubits are required to obtain quantum advantage over classical hardware. Neutral atoms are an excellent candidate for practical quantum computing, enabling large numbers...
Simple, paradigmatic systems are important tools in understanding strongly correlated systems. One such system is the Bose-Hubbard model, which can be realized using atoms in optical lattices with delta-function interactions. We report the first experimental observation of two features of the Bose-Hubbard model: superexchange via virtual molecules in excited bands and off-site contact...
We present a method for network-capable quantum computing that relies on holographic spin-wave excitations stored collectively in ensembles of qubits. This construction relies on an orthogonal basis of spin waves in a one-dimensional array and is capable of high-fidelity universal linear controllability using only phase shifts, applied in both momentum and position spaces. Neither single-site...
In the drive to develop cold-atom quantum technologies, compact vacuum systems are key to enabling quantum sensing for real world applications. These vacuum systems not only have to be reduced in size, weight, and power compared to their traditional counterparts, but face other challenges. Eliminating active pumping addresses both size and power, but introduces the issue of helium gas...
We realize, for the first time, a non-Abelian gauge theory with both gauge and matter fields on a quantum computer. This enables the observation of hadrons and the calculation of their associated masses. The SU(2) gauge group considered here represents an important first step towards ultimately studying quantum chromodynamics, the theory that describes the properties of protons, neutrons and...
Modern quantum sensors on the basis of ultra-cold atoms allow for an unprecedented experimental accuracy and have shown to be useful in fundamental science and real-world applications alike. With the advent of integration and miniaturization of such systems, the shrinking dimension of the setup leads to an increasing impact of the environment on the atoms’ dynamics.
To name only a few...
The interaction of quantum systems with themselves has been the subject of extensive theoretical[1] and experimental investigations [2,3]. Here, we present new results on the interaction of an ensemble of cold atoms with a time-delayed version of its own spontaneous emission light.
Experimentally, we form a magneto-optical trap (MOT) of caesium atoms around the waist of an optical...
A tomography of many-body quantum states of indistinguishable particles is generally performed by global couplings between the involved states and a subsequent counting of the occupation numbers. While precise couplings belong to the standard toolbox, an accurate number counting presents a considerable challenge for both photonic and atomic quantum states. Here we present an application of a...
Superradiant lasers are a promising path towards realizing a narrow-linewidth, high-precision and high-bandwidth active frequency reference [1]. They shift the phase memory from the optical cavity, which is subject to technical and thermal vibration noise, to an ultra-narrow optical atomic transition of an ensemble of cold atoms trapped inside the cavity. Our previous demonstration of pulsed...
Photon-mediated interactions between atoms coupled to an optical cavity are emerging as a powerful tool for engineering entangled states and many-body Hamiltonians. However, single-atom addressing and readout is not available in most of these systems.
Leveraging recent development in atom-tweezer arrays, we will present our current effort to combine the strong coupling regime at the...
Optical tweezer arrays combined with the rich internal structure of alkaline earth atoms enable explorations of new quantum systems for quantum optics, quantum simulation, and quantum computing. We report on our progress towards programmable arrays of strontium atoms generated with holographic metasurfaces. Innovations of our setup include: (1) Demonstration of a novel dispenser-based 2D MOT...
The complexity and variety of molecules offer opportunities for metrology and quantum information that go beyond what is possible with atomic systems. The hydrogen molecular ion is the simplest of all molecules and can thus be calculated ab initio to very high precision [1]. In combination with spectroscopy this allows to determine fundamental constants and test fundamental theory at record...
In relativistic geodesy, frequencies of distant optical clocks are compared to measure the relativistic redshift and thereby the geodetic height difference between the clocks. To obtain a height resolution of on the order of 1 cm, clocks with a fractional frequency uncertainty of 10-18 are required.
Here, we present a joint effort between PTB and DLR-SI to build a transportable aluminum ion...
Optical clocks have now reached accuracies close to 1 x $10^{-18}$ [1] [2]. Thanks to their extremely low uncertainties, they are used as tools for various applications, such as chronometric geodesy, tests of General Relativity, search for physics beyond the Standard Model or redefinition of the SI second [3].
Mercury has not been much investigated in cold atoms or quantum gas experiments,...
Finite-field optical magnetometry offers practical advantages in geophysics, surveying and navigation due to the sensitivity and accuracy achievable with alkali double-resonance techniques. In this sensor scheme, resonant modulation at the Larmor frequency is applied to the alkali spins in order to drive the resonant response and maximise signal contrast [1,2]. Homodyne detection also offers a...
The quantum simulation of Fermi-Hubbard models using ultracold atoms in optical lattices has been essential to deepen our understanding of condensed matter systems. With the precise tunability of the model parameters and the possibility to even change the dimensionality of the systems, it allows to investigate many-body quantum phases. In particular, probing spin correlations has been of...
The Standard Model of particle physics is one of the most successful models that we use to describe the universe, yet it is known to be incomplete. Substantial efforts on the theoretical front introduce new physics through extensions of the Standard Model, and these new physics models make predictions on the value of the electric dipole moment of the electron (eEDM). Measurements of (or...
The Leggett-Garg (LG) inequality tells us whether or not the dynamics of the macro- scopic system obeys macrorealism, which consists of the assumptions put forward by Leggett and Garg. Violation of the LG inequality implies either the absence of a realistic description of the system or the impossibility of measuring the system noninvasively. In recent works, the LG inequality is experimentally...
Optical tweezer arrays of Alkaline earth-like atoms are promising for applications in quantum information and metrology. Here, we describe a tweezer platform for trapping and manipulating arrays of $^{171}$Yb atoms [1]. We demonstrate favorable qubit properties of the nuclear spin $I=1/2$, including seconds-scale coherence times and sub-microsecond single-qubit gates. We further show that...
With our 6Li quantum gas microscope we are able to prepare, manipulate and image individual ultracold fermions in optical lattices. In every experimental run we have an access to full density and spin resolution [1], as well as to site-resolved potential shaping [2]. This platform has proven to be promising for the analog quantum simulation, e.g., of Fermi-Hubbard model which is believed to be...
The understanding of the interplay between quantum-statistical phenomena and the atomic interactions taking place in trapped degenerate gases may yet extend far our ability to control and harness the full potential of such exquisite, dilute quantum systems. In this scenario, a key role is played by the external trap potential, which defines the spatial dissociation of the condensate and...
Towards Feedback Cooling of a Single Trapped Ion in a Deep Parabolic Mirror
Atish Roy$^{1}$, Martin Fischer$^{1}$, Hans Dang$^{1,2}$, Lakhi Sharma$^{1}$, Markus Sondermann$^{2,1}$ and Gerd Leuchs$^{1,2,3,4}$
$^1$Max Planck Institute for the Science of Light, Erlangen, Germany
$^2$Friedrich-Alexander Universität Erlangen-Nürnberg, Department of Physics, Erlangen,...
