Speaker:	Jason Twamley (OIST)
Title:	Engineering quantum motion using magnetic forces for quantum sensing and exploring quantum gravity using table-top experiments.
Date (JST):	Tue, Jul 28, 2026, 15:30 - 17:00
Place:	Seminar Room A
Abstract:	The creation of macroscopic quantum states of massive systems allows one to begin to explore the boundaries between the classical and quantum worlds and, in particular, how gravity may interface with quantum mechanics. Levitated systems permit extreme isolation from decoherence [1], and such systems can be useful for quantum sensing such as in ultra-precise inertial sensors or for the detection of dark matter and forces [2], for quantum transduction and quantum memory where the quantum information is stored in long lived motional states of the levitated body and for more fundamental studies exploring the relationship between low-energy gravity and quantum mechanics [3]. In this talk I will discuss our recent theory and experiments on engineering massive (milligram) objects into quantum states of motion using magnetic forces. This includes diamagnetic levitation at room temperature of milligram objects in high vacuum. We show routes to obtain high motional Q−factors by engineering the object to suppress eddy currents [4, 5], how an axially symmetric levitated system need not generate any eddy currents at all [6], and plans for an optomechanical system with levitated mirror cooled to the ground state of motion using feedback. To generate macroscopic superpositions researchers have suggested using Stern-Gerlach spin dependent forces and recently observed spin dependent torques in small micro diamonds [7]. We describe our recent experiments at demonstrating such forces for centre of mass motion in macroscopic objects. [1] C. Gonzalez-Ballestero et al. “Levitodynamics: Levitation and control of microscopic objects in vacuum”. In: Science 374.6564 (Oct. 2021), p. 168. [2] F Monteiro et al. “Search for Composite Dark Matter with Optically Levitated Sensors”. In: Physical Review Letters 125.18 (Oct. 2020), p. 181102. [3] Sougato Bose et al. “Spin Entanglement Witness for Quantum Gravity”. In: Physical Review Letters 119.24 (2017), p. 240401. [4] P Romagnoli et al. “Controlling the motional quality factor of a diamagnetically levitated graphite plate”. In: Applied Physics Letters 122.9 (Feb. 2023), p. 2211.08764. [5] S Tian et al. “Feedback cooling of an insulating high-Q diamagnetically levitated plate”. In: Applied Physics Letters 124.12 (Mar. 2024). [6] D Kim et al. “A magnetically levitated conducting rotor with ultra-low rotational damping circumventing eddy loss”. In: Communications Physics 8.1 (2025), pp. 1–10. [7] A. Nayak et al. “Spin-force from a Nitrogen-Vacancy ensemble drives a 100 mg levitated resonator”. In: https://arxiv.org/abs/2605.17750

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