Exact description of transport and non-reciprocity in monitored quantum devices

TL;DR

This paper derives exact formulas for particle and heat flows in monitored quantum fermionic systems, revealing how measurement-induced inelastic processes create non-reciprocal currents and enable work extraction without feedback.

Contribution

It provides a non-perturbative formalism for understanding transport and non-reciprocity in monitored quantum systems, highlighting the role of measurement strength.

Findings

Measurement-induced inelastic processes cause non-reciprocal currents.

Optimal power or cooling occurs at specific monitoring strengths.

Exact formulas enable analysis beyond perturbative regimes.

Abstract

We study non-interacting fermionic systems undergoing continuous monitoring and driven by biased reservoirs. Averaging over the measurement outcomes, we derive exact formulas for the particle and heat flows in the system. We show that these currents feature competing elastic and inelastic components, which depend non-trivially on the monitoring strength $\gamma$. We highlight that monitor-induced inelastic processes lead to non-reciprocal currents, allowing to extract work from measurements without active feedback control. We illustrate our formalism with two distinct monitoring schemes providing measurement-induced power or cooling.~Optimal performances are found for values of the monitoring strength $\gamma$ which are hard to address with perturbative approaches.