Gravity mediated entanglement between light beams as a table-top test of quantum gravity

TL;DR

This paper proposes a tabletop experiment to test quantum gravity by demonstrating entanglement between light beams mediated by gravity, using a photonic protocol and path integral formalism to estimate entangling phases.

Contribution

It introduces a novel photonic approach to observe gravitationally induced entanglement, providing a theoretical framework and formulas for experimental implementation.

Findings

Derived a closed-form formula for the gravitational entangling phase.

Estimated photon numbers needed for observable entanglement.

Showed entanglement can be certified with lower phase signals.

Abstract

Over the past century, a large community within theoretical physics has been seeking a unified framework for quantum gravity. Yet, to date, there is still no experimental evidence of any non-classical features of gravity. While traditional experimental proposals would usually require immensely challenging Planck scale experiments, recent table-top protocols based on low-energy quantum control have opened a new avenue into the investigation of non-classical gravity. An approach that has sparked high interest, both in terms of experimental feasibility and of theoretical implications, is the indirect witnessing of non-classical gravity through the detection of its capacity to act as an entangling channel. Most discussions have been centred on the entanglement generation between two gravitationally coupled massive systems. In this work, we instead examine the entangling capacity of the gravitational interaction between two light pulses. We explain the main experimental and theoretical advantages of having a photonic protocol, and lay out the steps leading to the determination of the entangling phase, using the path integral formalism and linearised gravity. We establish a closed form formula for the entangling phase and provide an estimated order of magnitude of the average photon number required for the generation of appreciable phase. Using statistical analysis, we show how entanglement may be certified with lower phase signal.