Quantifying Quantumness in (A)dS spacetimes with Unruh-DeWitt Detector

Abstract: Probing quantumness in curved spacetime is regarded as one of fundamental and important topics in the framework of relativistic quantum information. In this work, we focus on the theoretical feasibility of probing quantum properties in de Sitter (dS) and Anti-de Sitter (AdS) spacetimes via detectors. By employing the Unruh-DeWitt detector coupled with a massless scalar field, which is treated as an open system, quantum uncertainty and quantum coherence in both dS and AdS spacetimes are investigated. Our analysis reveals that the acceleration in dS spacetime and the boundary conditions in AdS spacetime significantly impact the detector's evolution in the initial stage. Notably, both of the uncertainty and coherence will oscillate with the initial state being in a superposition state, however the high temperature is able to suppress their oscillation. Interestingly, it is found that the constant values of the final uncertainty and coherence are identical as those in dS and AdS spacetimes, which are determined by the ratio of energy gap to temperature. Hence, the current exploration offers insight into quantumness in dS and AdS spacetimes, and might be helpful to facilitate the curved-spacetime-based quantum information processing.