The influence of the Earth's curved spacetime on Gaussian quantum coherence

TL;DR

This paper investigates how Earth's curved spacetime influences Gaussian quantum coherence of photon pairs during satellite communication, revealing effects of gravitational frequency shifts and orbital parameters on quantum coherence.

Contribution

It demonstrates the impact of Earth's curved spacetime on Gaussian quantum coherence and explores how satellite height, bandwidth, and frequency affect this coherence.

Findings

Gaussian coherence increases with satellite height up to a point

Coherence is affected by Gaussian bandwidth and peak frequency

Gravitational frequency shifts cause less than 1% change in coherence

Abstract

Light wave-packets propagating from the Earth to satellites will be deformed by the curved background spacetime of the Earth, thus influencing the quantum state of light. We show that Gaussian coherence of photon pairs, which are initially prepared in a two-mode squeezed state, is affected by the curved spacetime background of the Earth. We demonstrate that quantum coherence of the state increases for a specific range of height h and then gradually approaches a finite value with further increasing height of the satellite's orbit in Kerr spacetime, because special relativistic effect are involved. Meanwhile, we find that Gaussian coherence increases with the increase of Gaussian bandwidth parameter, but the Gaussian coherence decreases with the growth of the peak frequency. In addition, we also find that total gravitational frequency shift causes changes of Gaussian coherence less than $%1$ and different initial peak frequencies also can effect rate of change with the satellite height in geostationary Earth orbits.