Ultimate precision: Gaussian parameter estimation in flat and curved spacetime

TL;DR

This paper develops a framework for optimal parameter estimation using mixed Gaussian states in relativistic quantum metrology, applicable to flat and curved spacetime, including finite temperature effects.

Contribution

It introduces a method to compute precision bounds for mixed Gaussian states, extending previous pure-state approaches in relativistic quantum metrology.

Findings

Framework for mixed Gaussian states in quantum field theory

Enables parameter estimation at finite temperature

Applicable to flat and curved spacetime scenarios

Abstract

Relativistic quantum metrology provides an optimal strategy for the estimation of parameters encoded in quantum fields in flat and curved spacetime. These parameters usually correspond to physical quantities of interest such as proper times, accelerations, gravitational field strengths, among other spacetime parameters. The precise estimation of these parameters can lead to novel applications in gravimeters, spacetime probes and gravitational wave detectors. Previous work in this direction only considered pure probe states. In realistic situations, however, probe states are mixed. In this paper, we provide a framework for the computation of optimal precision bounds for mixed single- and two-mode Gaussian states within quantum field theory. This enables the estimation of spacetime parameters in case the field states are initially at finite temperature.