Description
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 sensing to quantum computing, that require a fast and controlled current injection and a reliable read-out of its magnitude. Here I present the experimental realization of a fast and on-demand generation of persistent currents in atomic Fermi superfluid rings and the investigation of the connection between their damping and vortex nucleation. We excite persistent current states of on-demand winding number by dynamically imprinting the phase winding in the ring with a tailored laser beam and we read-out the current state via an interferometric probe, which directly accesses the ring phase profile. We demonstrate our method to efficiently excite persistent currents of finite and controllable winding in the different interaction regimes of the BEC-BCS crossover. We then induce the current decay by inserting a small defect in the ring. For currents higher than a critical value, the obstacle triggers the emission of vortices that reduce the phase winding. Our work demonstrates fast and accurate control of persistent currents in fermionic superfluids, opening the route for their application in quantum technologies.
| Presenter name | Giulia Del Pace |
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