Spontaneous emission as a bridge from Lindbladian to nonreciprocal reservoirs

TL;DR

This paper explores how spontaneous emission can create a bridge from traditional Lindbladian models to nonreciprocal, non-Hermitian reservoirs in quantum systems, with observable effects like the quantum Zeno effect, relevant for cold atom experiments.

Contribution

It demonstrates that effective descriptions of certain quantum systems require nonreciprocal couplings beyond Lindbladian formalism, linking spontaneous emission to non-Hermitian reservoir models.

Findings

Spontaneous emission induces nonreciprocal reservoir couplings.

Observable effects include the quantum Zeno effect in loss currents.

Connections to cold atom experiments are discussed.

Abstract

We study an out-of-equilibrium quantum system in which a state connecting two reservoirs is also coupled by stimulated and spontaneous emission of photons to an antitrapped state, thus implementing particle loss. After revisiting the spontaneous emission process, we show that the proper effective description of such a system requires one to go beyond the usual Lindbladian formalism and includes a nonreciprocal (``non-Hermitian'') coupling to the reservoir modeling the untrapped state. The presence of both, the reservoirs and the nonreciprocal coupling, have observable consequences that we compute, for example, by looking at the quantum Zeno effect in the loss current. We discuss the connection of our findings to possible experiments in cold atomic gases.