  One-way nonreciprocal interactions between two quantum systems are typically
described by a cascaded quantum master equation, and rely on an effective
breaking of time-reversal symmetry as well as the balancing of coherent and
dissipative interactions. Here, we present a new approach for obtaining
nonreciprocal quantum interactions that is completely distinct from cascaded
quantum systems, and that does not in general require broken TRS. Our method
relies on a local gauge symmetry present in any Markovian Lindblad master
equation. This new kind of quantum nonreciprocity has many implications,
including a new mechanism for performing dissipatively-stabilized gate
operations on a target quantum system. We also introduce a new, extremely
general quantum-information based metric for quantifying quantum
nonreciprocity.
