We are working with theorist Sougato Bose (UCL) towards testing the quantum nature of gravity using levitating microdiamonds containing nitrogen-vacancy (NV^-) centres. We would like to put the spin of an NV^- centre into a superposition and then an inhomogeneous magnetic field should put the microdiamond into a spatial superposition. The photo shows one of our levitated nanodiamonds as a green dot (due to the green laser light we are shining onto it). James March, Karishma Gokani and Anis Rahman are working on this in Warwick.

We have a five-year project called MAST-QG (Macroscopic superpositions towards witnessing the quantum nature of gravity) which is a collaboration with Yale, Northwestern, UCL and Groningen. This is funded by the Moore Foundation and the Sloan Foundation.

More details are in our papers:

17. James E March, Benjamin D Wood, Colin J Stephen, Soumen Mandal, Andrew M Edmonds, Daniel J Twitchen, Matthew L Markham, Oliver A Williams & Gavin W Morley, Long Spin Coherence and Relaxation Times in Nanodiamonds Milled from Polycrystalline ¹²C Diamond, Physical Review Applied 20, 044045 (2023), open access.

16. Eric Adelberger et al, Snowmass White Paper: Precision Studies of Spacetime Symmetries and Gravitational Physics, arXiv:2203.09691 (2022).

15. Daniel Carney et al, Snowmass 2021: Quantum Sensors for HEP Science -- Interferometers, Mechanics, Traps, and Clocks, arXiv:2203.07250 (2022).

14. Rainer Kaltenbaek et al, MAQRO -- BPS 2023 Research Campaign Whitepaper, arXiv:2202.01535 (2022).

13. BD Wood, GA Stimpson, JE March, YND Lekhai, CJ Stephen, BL Green, AC Frangeskou, L Ginés, S Mandal, OA Williams & GW Morley, Long Spin Coherence Times of Nitrogen Vacancy Centres in Milled Nanodiamonds, Physical Review B 105, 205401 (2022), preprint.

12. BD Wood, S Bose & GW Morley, Spin dynamical decoupling for generating macroscopic superpositions of a free-falling nanodiamond, Physical Review A 105, 012824 (2022), preprint.

11. Yue Ma, Thomas Guff, Gavin Morley, Igor Pikovski, M S Kim, Limits on inference of gravitational entanglement, Physical Review Research 4, 013024 (2022), open access.

10. Benjamin D Wood and Gavin W Morley, Review paper: Towards a test of quantum gravity with a levitated nanodiamond containing a spin, Proc. SPIE 11881, Quantum Technology: Driving Commercialisation of an Enabling Science II, 118810P (2021), arXiv:2110.14436.

9. Julen S Pedernales, Gavin W Morley & Martin B Plenio, Motional Dynamical Decoupling for Interferometry with Macroscopic Particles, Physical Review Letters 125, 023602 (2020). Open access.

8. Ryan J Marshman, Anupam Mazumdar, Gavin W Morley, Peter F Barker, Steven Hoekstra & Sougato Bose, Mesoscopic Interference for Metric and Curvature (MIMAC) & Gravitational Waves, New Journal of Physics 22, 083012 (2020). Open access. Highlighted in popular press including Scientific American and Physics World.

7. AC Frangeskou, ATMA Rahman, L Gines, S Mandal, OA Williams, PF Barker & GW Morley, Pure nanodiamonds for levitated optomechanics in vacuum, New Journal of Physics 20, 043016 (2018). Open access, open data.

6. ATM Anishur Rahman, AC Frangeskou, PF Barker & GW Morley, An analytical model for the detection of levitated nanoparticles in optomechanics, Review of Scientific Instruments 89, 023109 (2018). Open access, open data.

5. S Bose, A Mazumdar, GW Morley, H Ulbricht, M Toroš, M Paternostro, A Geraci, P Barker, MS Kim & G Milburn, A Spin Entanglement Witness for Quantum Gravity, Physical Review Letters 119, 240401 (2017), arXiv preprint. Highlighted in popular press including PRL Synopsis, New Scientist, Quanta and The Atlantic.

4. C Wan, M Scala, GW Morley, ATMA Rahman, H Ulbricht, J Bateman, PF Baker, S Bose, MS Kim, Free Nano-Object Ramsey Interferometry for Large Quantum Superpositions, Physical Review Letters 117, 143003 (2016). Open access.

3. ATMA Rahman, AC Frangeskou, MS Kim, S Bose, GW Morley & PF Barker, Burning and graphitization of optically levitated nanodiamonds in vacuum, Scientific Reports 6, 21633 (2016), arXiv preprint

2. C Wan, M Scala, S Bose, AC Frangeskou, ATMA Rahman, GW Morley, PF Barker & MS Kim, Tolerance in the Ramsey interference of a trapped nanodiamond, Physical Review A 93, 043852 (2016), arXiv preprint

1. M Scala, MS Kim, GW Morley, PF Barker & S Bose, Matter-wave interferometry of a levitated thermal nano-oscillator induced and probed by a spin, Physical Review Letters 111, 180403 (2013), arXiv preprint