Quantum metrology with open dynamical systems

TL;DR

This paper investigates the fundamental quantum limits of dynamical sensors affected by decoherence, providing tighter bounds for optical phase and force sensing that challenge the feasibility of Heisenberg scaling under realistic conditions.

Contribution

It introduces a modified purification approach to derive more accurate quantum error bounds in open systems, revealing shot-noise scaling limits in practical scenarios.

Findings

Quantum bounds obey shot-noise scaling with optical loss.

Heisenberg scaling is not achievable under realistic conditions.

Proposed bounds are experimentally approachable with current technology.

Abstract

This paper studies quantum limits to dynamical sensors in the presence of decoherence. A modified purification approach is used to obtain tighter quantum detection and estimation error bounds for optical phase sensing and optomechanical force sensing. When optical loss is present, these bounds are found to obey shot-noise scalings for arbitrary quantum states of light under certain realistic conditions, thus ruling out the possibility of asymptotic Heisenberg error scalings with respect to the average photon flux under those conditions. The proposed bounds are expected to be approachable using current quantum optics technology.