Quantum Gravity in a Laboratory?

by Nick Huggett, Niels Linnemann, Mike D. Schneider

The characteristic – Planck – energy scale of quantum gravity makes experimental access to the relevant physics apparently impossible. Nevertheless, low energy experiments linking gravity and the quantum have been the Page and Geilker quantum Cavendish experiment, and the Colella-Overhauser-Werner neutron interferometry experiment, for instance. However, neither probes states in which gravity remains in a coherent quantum superposition, unlike – it is claimed – recent proposals. In essence, if two initially unentangled subsystems interacting solely via gravity become entangled, then theorems of quantum mechanics show that gravity cannot be a classical subsystem. There are formidable challenges to such an experiment, but remarkably, tabletop technology into the gravity of very small bodies has advanced to the point that such an experiment might be feasible in the near future. This Element explains the proposal and what it aims to show, highlighting the important ways in which its interpretation is theory-laden.

98 pages, Paperback

Published August 3, 2023

Reviews

[Allan Olley · Rating 4 out of 5]

This is a short work introducing some debate about the potential to test the quantum nature of gravity with a relatively simple and not particularly exotic set-up where two objects whose mass would vary in response to a quantum process would mutually gravitate and evidence that this gravitational interaction lead to quantum entanglement (exotic effects of quantum statistics) would be measured. These objects are known as gravitational Schrodinger's cats or gravicats. The work explains some of the physics involved and also the controversy over what if anything the results of such experiments would show because of the complexities of untangled which assumptions our predictions depend on.

This is a very well argued and approachable account of some of the physics and the debate. There is some mathematical formalism and I will admit that I did not follow it because 20 years out of my undergrad in physics my shacky grasp of the relevant matrix mechanics has disappeared. Still I think it explains the principles involved without having to grasp the math. This is a very narrow subject and although some interesting philosophy of science and physics is invoked, it may be a bit too on such a narrow topic.

The pdf version I had worked fine for me and I did not notice any problems.