Experimental Demonstration of the Timelike Unruh Effect with a Trapped-Ion System

TL;DR

This paper demonstrates the timelike Unruh effect using a trapped-ion system, showing that a stationary detector can perceive a thermal response akin to the Unruh effect without requiring extreme accelerations.

Contribution

It provides the first experimental proof-of-principle of the timelike Unruh effect in a controllable quantum system, enabling laboratory exploration of relativistic quantum phenomena.

Findings

Detector exhibits thermal response to Minkowski vacuum

Demonstrates excitation and emission dynamics consistent with Unruh effect

Establishes a new platform for relativistic quantum physics experiments

Abstract

The Unruh effect predicts that an accelerated observer perceives the Minkowski vacuum as a thermal bath, but its direct observation requires extreme accelerations beyond current experimental reach. Foundational theory [Olson & Ralph, Phys. Rev. Lett. 106, 110404 (2011)] shows that an equivalent thermal response, known as the timelike Unruh effect, can occur for detectors following specific timelike trajectories without acceleration, enabling laboratory tests with stationary yet time-dependent detectors. Here, we report a proof-of-principle demonstration of the timelike Unruh effect in a quantum system of trapped ion, where a two-level spin serves as the detector and is temporally coupled to the ambient field encoded in the ion's vibrational motion. Specifically, we study both excitation and emission dynamics of the detector moving along a spacetime trajectory in the future/past light cone, and demonstrate the thermal response of the detector to the Minkowski vacuum that resembles the Unruh effect. This work establishes a controllable tabletop platform for exploring relativistic quantum physics under accessible laboratory conditions.