Nonclassicality as a Quantifiable Resource for Quantum Metrology

TL;DR

This paper introduces a quantifiable measure of nonclassicality as a resource for quantum metrology, demonstrating its operational significance in surpassing classical limits in displacement and phase sensing.

Contribution

It defines the metrological power as a resource measure based on quantum Fisher information, linking nonclassicality to enhanced quantum sensing capabilities.

Findings

Single highly nonclassical states outperform multiple moderately nonclassical states.

Metrological power correlates with quantum macroscopicity.

Resources for displacement sensing can be converted into phase sensitivity enhancements.

Abstract

We establish the nonclassicality of continuous-variable states as a resource for quantum metrology. Based on the quantum Fisher information of multimode quadratures, we introduce the metrological power as a measure of nonclassicality with a concrete operational meaning of displacement sensitivity beyond the classical limit. This measure belongs to the resource theory of nonclassicality, which is nonincreasing under linear optical elements. Our Letter reveals that a single copy, highly nonclassical quantum state is intrinsically advantageous when compared to multiple copies of a quantum state with moderate nonclassicality. This suggests that metrological power is related to the degree of quantum macroscopicity. Finally, we demonstrate that metrological resources useful for nonclassical displacement sensing tasks can be always converted into a useful resource state for phase sensitivity beyond the classical limit.