TG QOSMIG: Talk by Andrea Vinante about levitated nanomagnets

I will give an overview of current efforts in developing experimental platforms to levitate micro/nanomagnets and to exploit these systems for sensing. The most peculiar feature of levitated particles is the very high degree of isolation from the environment, and as a consequence low thermal noise and decoherence. Levitated magnets offer the additional benefit of being extremely sensitive to magnetic fields and rotations, suggesting a number of applications in the context of fundamental physics. Several trapped levitation schemes are currently explored, including electrical, magnetic and superconducting traps. A complementary approach is investigating free-fall micromagnets in a microgravity environment. I will describe in more detail our effort in levitating micromagnets by Meissner effect in a gravitational-superconducting trap, using SQUIDs as motion detectors. Preliminary measurements show that levitation can be realized in agreement with the Meissner effect, featuring ultralow damping rate of rotational and translational modes in the 1E-5 Hz range. Finally, I will discuss possible applications of levitated ferromagnets, which include for instance tests of wave function collapse models and investigations of exotic interactions beyond the standard model. Remarkably, a torque sensor based on a levitated micromagnet is expected to overcome the Standard Quantum Limit on magnetometry, and to surpass by orders of magnitude the Energy Resolution Limit, often proposed as a conventional benchmark for ultrasensitive magnetometers. This goal may be achieved either in the gyroscopic atom-like regime, with the magnet featuring macroscopic Larmor precession [1], or in the more common librational trapped regime [2].

[1] D.F. Jackson Kimball et al., Precessing Ferromagnetic Needle Magnetometer, Phys. Rev. Lett. 116, 190801 (2016).

[2] A. Vinante et al., Surpassing the Energy Resolution Limit with ferromagnetic torque sensors, Phys. Rev. Lett. 127, 070801 (2021).