Global sensing and its impact for quantum many-body probes with criticality

TL;DR

This paper introduces a systematic approach for optimizing quantum many-body probes for global sensing, leveraging criticality to enhance precision over large parameter ranges without prior information.

Contribution

It develops a protocol to tune control fields in many-body quantum probes, enabling effective global sensing by exploiting quantum criticality, especially in Ising models.

Findings

Optimized control fields improve sensing precision at critical points.

The protocol enhances performance even with simple measurements.

Multi-parameter sensing benefits from criticality along the entire phase line.

Abstract

Quantum sensing is one of the key areas which exemplifies the superiority of quantum technologies. Nonetheless, most quantum sensing protocols operate efficiently only when the unknown parameters vary within a very narrow region, i.e., local sensing. Here, we provide a systematic formulation for quantifying the precision of a probe for multi-parameter global sensing when there is no prior information about the parameters. In many-body probes, in which extra tunable parameters exist, our protocol can tune the performance for harnessing the quantum criticality over arbitrarily large sensing intervals. For the single-parameter sensing, our protocol optimizes a control field such that an Ising probe is tuned to always operate around its criticality. This significantly enhances the performance of the probe even when the interval of interest is so large that the precision is bounded by the standard limit. For the multi-parameter case, our protocol optimizes the control fields such that the probe operates at the most efficient point along its critical line. Interestingly, for an Ising probe, it is predominantly determined by the longitudinal field. Finally, we show that even a simple magnetization measurement significantly benefits from our optimization and moderately delivers the theoretical precision.