Relaxation of experimental parameters in a Quantum-Gravity Induced Entanglement of Masses Protocol using electromagnetic screening

TL;DR

This paper analyzes how electromagnetic interactions and imperfections affect the feasibility of testing quantum gravity through entanglement experiments with nano-crystals, proposing methods to mitigate these effects.

Contribution

It provides a detailed estimation of EM-induced dephasing, systematic errors, and constraints on superposition size in a parallel QGEM setup, enhancing experimental robustness.

Findings

Electromagnetic interactions can cause significant dephasing in QGEM experiments.

Imperfections like permanent dipoles contribute to EM background and dephasing.

Constraints on superposition size are derived in a model-independent manner.

Abstract

To test the quantum nature of gravity in a lab requires witnessing the entanglement between the two test masses (nano-crystals) solely due to the gravitational interaction kept at a distance in a spatial superposition. The protocol is known as the quantum gravity-induced entanglement of masses (QGEM). One of the main backgrounds in the QGEM experiment is electromagnetic (EM) induced entanglement and decoherence. The EM interactions can entangle the two neutral masses via dipole-dipole vacuum-induced interactions, such as the Casimir-Polder interaction. To mitigate the EM-induced interactions between the two nano-crystals, we enclose the two interferometers in a Faraday cage and separate them by a conducting plate. However, any imperfection on the surface of a nano-crystal, such as a permanent dipole moment will also create an EM background interacting with the conducting plate in the experimental box. These interactions will further generate EM-induced dephasing which we wish to mitigate. In this paper, we will consider a parallel configuration of the QGEM experiment, where we will estimate the EM-induced dephasing rate, run-by-run systematic errors which will induce dephasing, and also provide constraints on the size of the superposition in a model-independent way of creating the spatial superposition.