Entanglement-enhanced quantum ranging in the near-Earth spacetime

TL;DR

This paper introduces a quantum ranging protocol that leverages entanglement and multiple hypothesis testing to accurately determine distances in near-Earth curved spacetime, outperforming flat spacetime methods.

Contribution

It develops a novel quantum ranging scheme accounting for Earth's gravity effects, demonstrating advantages over flat spacetime approaches and analyzing the impact of gravitational shifts and transmitted modes.

Findings

Quantum ranging benefits from Earth's gravity effects are significant.

Maximum advantage is achieved with increased transmitted modes.

Dividing the range into slices does not sharply improve performance.

Abstract

We propose a quantum ranging protocol to determine the distance between an observer and a target at the line of sight in the near-Earth curved spacetime. Unlike the quantum illumination scheme, here we employ multiple quantum hypothesis testing to decide the presence and location of the target at the same time. In the present protocol, the gravity of the Earth influences the propagation of photons and the performance of quantum ranging. We find that the maximum potential advantages of the quantum ranging strategy in the curved spacetime outperform its flat spacetime counterpart. This is because the effect of gravitational red-shift and blue-shift on the entangled signal photons can be canceled out, while the thermal photons only suffers from the gravitational blue-shift effect. We also show that the number of transmitted modes can promote the maximum potential advantage of the quantum ranging tasks. The maximum potential advantage of quantum ranging in the curved spacetime can not be raised sharply by dividing the range into multiple slices.