Gravitational wave imprints on spontaneous emission

TL;DR

This paper shows that gravitational waves can influence spontaneous emission in atoms, causing detectable changes in emission spectra, which could enable new methods for observing low-frequency gravitational waves using cold-atom experiments.

Contribution

It introduces the concept that gravitational waves affect atomic spontaneous emission spectra, providing a novel way to detect low-frequency gravitational waves through quantum optical effects.

Findings

Gravitational waves cause a direction-dependent change in atomic emission spectra.

Total decay rates remain unchanged, but the atom-field system evolution is affected.

The effect is measurable with current cold-atom experimental setups.

Abstract

Despite growing interest, there is a scarcity of known predictions in the regime where both quantum and general relativistic effects become observable. Here, we investigate a combined atom-field system in a curved spacetime, with a specific focus on gravitational-wave backgrounds. We demonstrate that a plane gravitational wave alters spontaneous emission from a single atom, manifesting itself as a direction-dependent change in the emission spectrum. Although the total decay rate remains unchanged, implying that no information about the gravitational wave is stored in the atomic internal state alone, the wave leaves imprints on the evolution of the composite atom-field system. To quantify how well this effect can be measured, we analyze both the classical Fisher information associated with photon number measurements and the quantum Fisher information. Our analysis indicates that the effect could be measured in state-of-the-art cold-atom experiments and points to spontaneous emission as a potential probe of low-frequency gravitational waves.