Magnetic field fluctuations induced decoherence of a diamagnetic nanosphere

Abstract This paper provides a simple derivation of the decoherence rate for a diamagnetic nanoparticle in
the presence of fluctuations of the magnetic field in a thermal environment. Diamagnetic levitation
is one of the key techniques for trapping, cooling, and creating a macroscopic quantum spatial
superposition in many experiments. It is widely applied in many theoretical and experimental
endeavours to test fundamental physics in matter-wave interferometers. To estimate the decoherence
rate originating from magnetic-field fluctuations, we use the fluctuation-dissipation theorem. We
show that our resulting decoherence rate expression is analogous to that of a dielectric material
interacting with the electric field component of the background field; however, it is often relatively
suppressed due to the material properties.