  The breaking of reciprocity is a topic of great interest in fundamental
physics and optical information processing applications. We demonstrate
non-reciprocal light transport in a quantum system of hot atoms by engineering
the dissipative atomic reservoir. Our scheme is based on the phase-sensitive
light transport in a multi-channel photon-atom interaction configuration, where
the phase of collective atomic excitations is tunable through external driving
fields. Remarkably, we observe inter-channel quantum correlations which
originate from interactions with the judiciously engineered reservoir. The
non-reciprocal transport in a quantum optical atomic system constitutes a new
paradigm for atom-based, non-reciprocal optics, and offers opportunities for
quantum simulations with coupled optical channels.
