Quantum metrology with a continuous-variable system

TL;DR

This paper reviews quantum metrology using continuous-variable systems, analyzing precision limits, optimal strategies, and experimental platforms for enhanced measurement sensitivity in quantum technologies.

Contribution

It provides a comprehensive comparison of fundamental quantum Fisher information limits with practical measurement strategies in continuous-variable quantum metrology.

Findings

Gaussian states and superpositions offer high sensitivities

Quantum Fisher information sets fundamental precision bounds

Experimental platforms include quantum light, ions, and mechanical oscillators

Abstract

As one of the main pillars of quantum technologies, quantum metrology aims to improve measurement precision using techniques from quantum information. The two main strategies to achieve this are the preparation of nonclassical states and the design of optimized measurement observables. We discuss precision limits and optimal strategies in quantum metrology and sensing with a single mode of quantum continuous variables. We focus on the practically most relevant cases of estimating displacements and rotations and provide the sensitivities of the most important classes of states that includes Gaussian states and superpositions of Fock states or coherent states. Fundamental precision limits that are obtained from the quantum Fisher information are compared to the precision of a simple moment-based estimation strategy based on the data obtained from possibly sub-optimal measurement observables, including homodyne, photon number, parity and higher moments. Finally, we summarize some of the main experimental achievements and present emerging platforms for continuous-variable sensing. These results are of particular interest for experiments with quantum light, trapped ions, mechanical oscillators, and microwave resonators.