Dr Richard Howl (Royal Holloway, University of London)

Testing quantum gravity in the laboratory was long thought impossible. However, recent advances in quantum technology have challenged this view. By placing a massive, mesoscopic object in a quantum state, it is possible, in principle, to investigate the behaviour of the gravitational field of the quantum object. So far, only gravitational fields of classical sources have been observed, but a quantum source mass will enable us to determine whether gravity, and thus spacetime geometry, is quantized, presenting a first test of quantum gravity [1-4]. However, although progress in quantum technology continues to scale up quantum theory to larger objects, the masses and techniques required remain challenging. I will review the current state of the field and discuss recent work [5-6] that suggests that ultracold atoms could be ideal systems for testing quantum gravity with quantum technology, overcoming several of the present challenges.

[1] S Bose, A Mazumdar, GW Morley, H Ulbricht, M Toroš, M Paternostro, A Geraci, P Barker, MS Kim, G Milburn, PRL 119, 240401 (2017)

[2] C Marletto, V Vedral, PRL 119, 240402 (2017)

[3] M Christodoulou, A Di Biagio, M Aspelmeyer, Č Brukner, C Rovelli, R Howl, PRL 130, 100202 (2023)

[4] M Christodoulou,  A Di Biagio, R Howl, C Rovelli, Class. Quantum Grav. 40 04700 (2023)

[5] R Howl, V Vedral, D Naik, M Christodoulou, C Rovelli, A Iyer, PRX Quantum 2, 010325 (2021)

[6] R Howl, N Cooper, L Hackermüller, arXiv:2304.00734 (2023)