Chiral-coupling-assisted refrigeration and superior dark-state sideband cooling in trapped atoms

Cooling the trapped atoms toward their motional ground states is key to applications of quantum simulation and quantum computation. Here we demonstrate the capability of light-mediated chiral couplings between atoms, which enables a superior cooling scheme exceeding the single-atom limit of sideband cooling. We present the chiral-coupling-assisted refrigeration in the target atom at the price of heating the others under asymmetric drivings, where its steady-state phonon occupation outperforms the lower bound set by a single atom. By utilizing nonreciprocal couplings between two atoms, we also present an intriguing dark-state cooling scheme in Λ-type three-level structure, which is shown superior than the conventional electromagnetically-induced-transparency cooling in a single atom. Our results present a resource of collective chiral couplings which help surpass the bottleneck of cooling procedure in applications of trapped-atom-based quantum computer and simulator.