Quantum jump metrology in a two-cavity network

TL;DR

This paper demonstrates that quantum jump metrology in a two-cavity optical network with quantum feedback can surpass the standard quantum limit, offering a scalable and practical alternative to entangled-state-based quantum metrology.

Contribution

It introduces a novel quantum jump metrology scheme using quantum feedback in a two-cavity system to improve measurement precision without complex entangled states.

Findings

Exceeds the standard quantum limit in phase measurement

Uses quantum feedback with laser pulses for enhanced sensitivity

Scalable and more practical than previous quantum metrology schemes

Abstract

Quantum metrology enhances measurement precision by utilising the properties of quantum physics. In interferometry, this is typically achieved by evolving highly-entangled quantum states before performing single-shot measurements to reveal information about an unknown parameter. While this is often the optimum approach, implementation with all but the smallest states is still extremely challenging. An alternative approach is quantum jump metrology [L. A. Clark et al., Phys. Rev. A 99, 022102 (2019)] which deduces information by continuously monitoring an open quantum system, while inducing phase-dependent temporal correlations with the help of quantum feedback. Taking this approach here, we analyse measurements of a relative phase in an optical network of two cavities with quantum feedback in the form of laser pulses. It is shown that the proposed approach can exceed the standard quantum limit without the need for complex quantum states while being scalable and more practical than previous related schemes.