Precision optomechanical systems to test fundamental physics

Speaker: Michael Tobar, The University of Western Australia.

One of the greatest challenges of physics is to unite the successful theories of quantum mechanics (QM) and general relativity (GR), into a unified theory of quantum gravity (QG). This goal has challenged physicists for several decades but they continue to seem incompatible. To discover QG, experimental observations should guide theory in a similar way as experimental observations guided the development of QM. To avoid high energies at the Planck scale, based on a minimum length (assumed to be the order of the Planck length 1.6x10^{−35m}), a new way to test a set of QG theories using precise measurement of a massive optomechanical system was suggested [1]. This leads to the concept of the generalized uncertainty principle (GUP), where the mass of the object changes may change the Heisenberg uncertainty relation. We will report results from our recently performed test of GUP, performed thorough precision measurements of induced frequency perturbations on high-Q acoustic resonators [2]. We show three orders of magnitude improvement over our prior measurements [3]. Using state-of the art precision metrology, we predict orders of magnitude improvement is possible, into the quantum regime. 
With Similar acoustic setups to those above, we may also perform sensitive searches for high-frequency gravitational waves. New results from the Multimode Acoustic Gravitational Wave Experiment (MAGE), where we search for MHz gravitational wave events by correlating two acoustic oscillators, will also be presented [4-7]. Other experiments we have undertaken to tests fundamental physics using acoustic technology, include the search for scalar dark matter [8], and the search for Lorentz invariance violations [9,10].


References
[1] I Pikovski et al, Probing Planck scale physics with quantum optics, Nat. Phys. 8, 393, 2012.
[2] W Campbell, ME Tobar, S Galliou, M Goryachev, Improved Constraints on the Minimum Length with a Macroscopic Low Loss Phonon Cavity, PRD 108, 102006, 2023. 
[3] P Bushev, J Bourhill, M Goryachev, N Kukharchyk, E Ivanov, S Galliou, ME Tobar, S Danilishin, Testing the generalized uncertainty principle with macroscopic mechanical oscillators and pendulums, PRD 100, 066020, 2019. 
[4] M Goryachev, ME Tobar, Gravitational wave detection with high frequency phonon trapping acoustic cavities, PRD 90, 102005, 2014. 
[5] ME Tobar, Cryogenic Optomechanics and the Resurgence of the Resonant-Mass Gravitational Wave Detector, NJP 19, 091001, 2017. 
[6] M Goryachev, W Campbell, I Heng, S Galliou, E Ivanov, ME Tobar, Rare events detected with a Bulk Acoustic Wave High Frequency Gravitational Wave antenna, PRL 127, 071102, 2021. 
[7] N Aggarwal, et al, Living Reviews in Relativity, 24 4, 2021.
[8] W Campbell, B McAllister, M Goryachev, E Ivanov, ME Tobar, Searching for scalar dark matter via coupling to fundamental constants with photonic, atomic, and mechanical oscillators, PRL 126, 071301, 2021.