Non-reciprocal population dynamics in a quantum trimer

TL;DR

This paper investigates how complex phases in a quantum trimer influence population dynamics and steady states, revealing nonreciprocal behavior and chiral currents that depend on phase, coupling, and gain, with implications for nanoscale experiments.

Contribution

It introduces the effect of complex phase modulation in a quantum trimer on nonreciprocal population dynamics and chiral currents, extending understanding beyond single-excitation models.

Findings

Population dynamics depend on accumulated phase.

Steady states exhibit nonreciprocal behavior.

Chiral current directionality is tunable by phase and gain.

Abstract

We study a quantum trimer of coupled two-level systems beyond the single-excitation sector, where the coherent coupling constants are ornamented by a complex phase. Accounting for losses and gain in an open quantum systems approach, we show how the mean populations of the states in the system crucially depend on the accumulated phase in the trimer. Namely, for nontrivial accumulated phases, the population dynamics and the steady states display remarkable nonreciprocal behavior in both the singly and doubly excited manifolds. Furthermore, while the directionality of the resultant chiral current is primarily determined by the accumulated phase in the loop, the sign of the flow may also change depending on the coupling strength and the amount of gain in the system. This directionality paves the way for experimental studies of chiral currents at the nanoscale, where the phases of the complex hopping parameters are modulated by magnetic or synthetic magnetic fields.14 pages