Fundamental limits on nonequilibrium sensing

TL;DR

This paper explores the fundamental physical limits of nonequilibrium sensing in bipartite systems, demonstrating how nonreciprocal coupling can enhance sensor performance beyond equilibrium constraints.

Contribution

It introduces a theoretical framework showing how a Maxwell's demon-like subsystem can suppress fluctuations and improve sensing in nonequilibrium systems.

Findings

Negative fluctuation-dissipation violation enhances SNR

Nonequilibrium SNR can be arbitrarily large at low frequencies

Enhanced sensing occurs with fixed dissipation levels

Abstract

The performance of equilibrium sensors is restricted by the laws of equilibrium thermodynamics. We here investigate the physical limits on nonequilibrium sensing in bipartite systems with nonreciprocal coupling. We show that one of the subsystems, acting as a Maxwell's demon, can significantly suppress the fluctuations of the other subsystem relative to its response to an external perturbation. Such negative violation of the fluctuation-dissipation relation can considerably improve the signal-to-noise ratio above its corresponding equilibrium value, allowing the subsystem to operate as an enhanced sensor. We find that the nonequilibrium signal-to-noise ratio of linear systems may be arbitrary large at low frequencies, even at a fixed overall amount of dissipation.