Precision in estimating Unruh temperature

Abstract

The goal of quantum metrology is the exploitation of quantum resources, like entanglement or quantum coherence, in the fundamental task of parameter estimation. Here we consider the question of the estimation of the Unruh temperature in the scenario of relativistic quantum metrology. Specifically, we study two distinct cases. First, a single Unruh-DeWitt detector interacting with a scalar quantum field undergoes an uniform acceleration for a finite amount of proper time, and the role of coherence in the estimation process is analyzed. After this, we consider two initially entangled detectors, one of which is inertial while the other one undergoes acceleration. Our results show that the maximum of the Fisher information, thus characterizing the maximum possible precision according to Crammér-Rao bound, occurs only for small accelerations, while it decreases fast when acceleration increases. Moreover, the role of initial coherence -in the single detector case-, or entanglement -in the two detectors case-, is to decrease Fisher information. Therefore, under the considered protocol, internal coherence (or entanglement) is not a resource for estimating Unruh temperature. These unexpected results show that a detection of the Unruh effect can be even more challenge than previously thought. Finally, by considering the connection between Unruh effect and Hawking radiation, we discuss how our results can be understood in the context of the estimation of Hawking temperature.

Fisher information as a probe of spacetime structure: Relativistic quantum metrology in (A)dS

“…It is especially interesting when the quantity being measured is a parameter governing some phenomenon in which both quantum and gravitational effects are present. Previous research has investigated the metrology of a wide range of relativistic phenomena, including acceleration [7], the Unruh-Hawking effect [8,9], the expansion rate of a Robertson-Walker universe [10], Bose-Einstein condensates [11][12][13], and Schwarzschild spacetime parameters [14].…”