Optimal Quantum Metrology for Probing the Unruh Effect with Uniformly Accelerated Two-Level Atoms

Abstract

We develop a quantum metrological framework for optimizing the probing of the Unruh effect using uniformly accelerated two-level atomic probes. The acceleration-dependent factor generated during the atom--field interaction is encoded in the atomic state and can be estimated through repeated quantum measurements. For a fixed total probe time, which characterizes the available measurement resource, we optimize the interrogation time of individual probes, the initial atomic state, and the corresponding measurement basis to minimize the estimation uncertainty. We show that the achievable precision is governed by the Fisher information accumulated per unit probe time. Under a fixed total probe time, shorter evolution times of individual probes allow for more sequential measurements, leading to a significant improvement in the estimation precision. The optimal initial state and measurement basis depend on both the acceleration factor and the probe evolution time. In particular, the excited state provides superior sensitivity in the weak-acceleration regime, whereas the ground state becomes advantageous for sufficiently large acceleration and long interaction times. Furthermore, we determine the minimum total probe time required to resolve the acceleration-dependent signal associated with the Unruh effect and demonstrate that this requirement can be substantially reduced by employing atomic systems with larger transition dipole moments. Our results establish an optimized quantum metrological strategy for probing acceleration-induced quantum effects and provide a systematic approach toward the experimental investigation of the Unruh effect.