Beating joint quantum estimation limits with stepwise multiparameter metrology

TL;DR

This paper introduces a stepwise multiparameter quantum sensing method that surpasses traditional joint estimation limits by effectively handling measurement incompatibility and parameter interdependencies, achieving superior precision in various quantum sensing scenarios.

Contribution

The authors propose and demonstrate a stepwise estimation approach that outperforms joint estimation in quantum metrology, especially with multiple sensors and many-body probes.

Findings

Stepwise sensing achieves lower error bounds than joint estimation.

Quantum-enhanced scaling is preserved with many-body probes using stepwise methods.

Bayesian implementations confirm the practical advantages of the proposed approach.

Abstract

Conventional multiparameter quantum sensing relies on joint estimation, but this approach faces two key limitations: theoretical bounds may be unattainable due to measurement incompatibility, and sensing may fail due to parameter interdependencies. We propose stepwise estimation and identify regimes where it outperforms joint estimation. For multiple quantum sensors, this scheme achieves far lower error bounds than joint estimation. With many-body probes, stepwise sensing retains a quantum-enhanced scaling advantage often lost in joint estimation due to parameter correlations. We demonstrate its concrete advantages through Bayesian implementations across diverse examples.