Gravitational photon echo

TL;DR

This paper theoretically explores the generation, control, and storage of gravitationally induced photon echoes using the Thorium-229 nuclear clock transition, aiming to enable gravitational quantum optics experiments on Earth.

Contribution

It introduces a novel theoretical framework for gravitational photon echoes leveraging the unique properties of Thorium-229's nuclear transition.

Findings

Potential detection of gravitational-redshift effects at millimeter scales.

Feasibility of controlling photon echoes via gravitational frequency shifts.

Foundation for gravitational quantum optics experiments on Earth.

Abstract

The generation, controls, and storage of the gravitationally induced photon echo using the 8.4 eV Thorium-229 nuclear clock transition on Earth are theoretically investigated. With its exceptionally narrow linewidth of approximately 1 mHz and high quality factor in the order of $10^{19}$, the Thorium-229 clock transition allows for the potential detection of gravitational-redshift effects at millimeter-scale altitude variations. Moreover, the 1740-second half lifetime of the Thorium-229 isomeric state allows for the slow movement of the system within its coherence time. Along this line, we explore the generation, controls, and storage of photon echo arising from a rotation induced inversion of the gravitational frequency shift in a single target or in multiple equally spaced samples. Our approach lays the foundation for the controllable gravitational quantum optics on Earth.