Coherent phase slips in coupled matter-wave circuits

Quantum phase slips are a dual process of particle tunneling in coherent networks. Besides being of central interest to condensed matter physics, quantum phase slips are resources that are sought to be manipulated in quantum circuits. Here, we devise a specific matter-wave circuit enlightening quantum phase slips. Specifically, we investigate the quantum many-body dynamics of two side-by-side ring-shaped neutral bosonic systems coupled through a weak link. By imparting a suitable magnetic flux, persistent currents flow in each ring with given winding numbers. We demonstrate that coherent phase slips occur as winding number transfer among the two rings, with the populations in each ring remaining nearly constant. Such a phenomenon occurs as a result of a specific entanglement of circulating states, that, as such, cannot be captured by a mean-field treatment of the system. Our work can be relevant for the observation of quantum phase slips in cold-atom experiments and their manipulation in matter-wave circuits. To make contact with the field, we show that the phenomenon has clear signatures in the momentum distribution of the system providing the time-of-flight image of the condensate. We thank G. Catelani and W. Jordan Chetcuti for discussion. A.P.-O. acknowledges financial support from Secretaria d'Universitats i Recerca del Departament d'Empresa i Coneixement de la Generalitat de Catalunya cofunded by the European Union Regional Development Fund within the ERDF Operational Program of Catalunya (project QuantumCat, Ref. No. 001-P-001644).