Nonreciprocal Quantum Sensing

TL;DR

This paper demonstrates that nonreciprocal quantum coupling enhances sensing precision and noise robustness, with potential improvements up to quadratic scaling using multiple couplings and optimal measurement strategies.

Contribution

It introduces the advantage of nonreciprocal coupling in quantum sensing, showing significant precision gains and noise resilience over reciprocal systems.

Findings

Nonreciprocal coupling outperforms reciprocal coupling in sensing accuracy.

Homodyne measurement is identified as optimal for nonreciprocal sensing.

Multiple nonreciprocal couplings can achieve quadratic improvements in measurement precision.

Abstract

Nonreciprocity can not only generate quantum resources, but also shield noise and reverse interference from driving signals. We investigate the advantages of nonreciprocal coupling in sensing a driving signal. In general, we find that the nonreciprocal coupling performs better than the corresponding reciprocal coupling. And we show that homodyne measurement is the optimal measurement. A single non-reciprocal coupling can increase measurement precision up to 2 times. Using $N$ non-reciprocal couplings in parallel, the measurement precision can be improved by $N^2$ times compared with the corresponding reciprocal coupling. In a non-zero temperature dissipative environment, we demonstrate that the nonreciprocal quantum sensing has better robustness to thermal noise than the reciprocal quantum sensing.