Parameter scanning in a quantum-gravity-induced entanglement of masses (QGEM) experiment with electromagnetic screening

TL;DR

This paper explores parameter optimization for the QGEM experiment, demonstrating that electromagnetic screening allows for smaller superpositions of about a micron size with feasible decoherence rates, advancing the experimental prospects of observing quantum gravity effects.

Contribution

It provides a detailed parameter scan considering electromagnetic screening, showing that smaller superpositions are sufficient for detecting quantum gravity-induced entanglement.

Findings

Superpositions of at least a micron size are required.

Electromagnetic screening reduces the necessary superposition size.

Feasible decoherence rates (~10^{-3} Hz) are compatible with experimental setups.

Abstract

Witnessing the quantum nature of spacetime is an exceptionally challenging task. However, the quantum gravity-induced entanglement of matter (QGEM) protocol proposes such a test by testing entanglement between adjacent matter-wave interferometers. One key obstacle to experimentally realising this protocol is the creation of a spatial quantum superposition with heavy masses. Initially, it was envisaged that the superposition size would have to be of order 200 micron for a mass $10^{-14}$ kg (to obtain the entanglement phase of order unity when the centre of mass of the two interferometers are at a separation of 450 microns). The experimental design has since improved, e.g. by assuming that the two interferometers are separated by an electromagnetic screen, which helps bring the separation distance close to 35 micron. Here, we do parameter scans taking into account the electromagnetic screening, and we consider different geometrical setups; we show superpositions of at least a micron-size for mass $10^{-14}$ kg with a decoherence rate of order $10^{-3}$ Hz are required.