Sequential Measurements as a Resource for Quantum Metrology

TL;DR

This paper introduces a quantum metrology protocol using sequential weak measurements on a harmonic oscillator to enhance information extraction, robustness, and dynamic range in estimating displacement channels.

Contribution

It demonstrates that measurement backaction can boost information gain and that post-processing mitigates phase wrapping, advancing single- and multi-parameter quantum sensing.

Findings

Measurement backaction increases information gain across measurement strengths.

Post-processing extends the effective dynamic range by avoiding phase wrapping.

Periodic information extraction enhances robustness to decoherence.

Abstract

We present a protocol in which sequential weak measurements of a quantum harmonic oscillator enable simultaneous estimation of both quadratures of a displacement channel. Calculations of the quantum Fisher information show that the measurement backaction can increase the information gained for a range of measurement strengths. The protocol distributes information over a $N$-bit string after $N$ weak measurements. Thus we find that post-processing can be used to avoid information loss due to phase wrapping, increasing the effective dynamic range. Finally, the periodic information extraction makes the protocol robust to decoherence. Our results establish mid-sensing measurement as a resource for single- and multi-parameter quantum metrology.