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 exponentially large Hilbert space size – and also from the intrinsically open and non-equilibrium nature of waveguide QED systems. Recently, it has been theorized that the dynamics in disordered waveguide QED systems can exhibit a many-body localized phase, where the underlying Hamiltonian becomes diagonalizable in terms of local integrals of motion and the dynamics can be solved in a non-perturbative fashion. Moreover, a dynamical phase transition is predicted between delocalized, many-body localized, and Anderson localized phases as a function of the density of excitations in the system. We hypothesize that the microscopic mechanism responsible for said phase transition is the formation of extended “necklace” states that facilitate transport across the system. These states are formed by the hybridization of localized modes of different resonance frequencies that span the system length, and can facilitate tunneling of photons in combination with interactions in the form of quantum nonlinear frequency mixing. We discuss our ongoing efforts to show that these quantum necklace states dominate quantum transport of photons in disordered waveguide QED, and how they manifest themselves in accessible observables like the transmission spectra, two-photon correlations, and their fluctuations.
|Presenter name||Daniel Goncalves Romeu|
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