Diamagnetic levitation of a milligram-scale silica using permanent magnets for the use in a macroscopic quantum measurement

Abstract

Verification of macroscopic quantum mechanics requires that the position measurement accuracy of mirrors of various mass scales reach the Standard Quantum Limit (SQL) derived from Heisenberg's uncertainty principle. At mg-scale, thermal noise of the suspension wire of the mirror is an issue to reach the SQL. We propose to use a magnetic levitation system consisting of permanent magnets and yokes, noting the fact that a silica mirror is diamagnetic, and have succeeded in the experimental verification to levitate a 0.1-1 mg silica mass. This is the first demonstration of the levitation system with this mass scale and this magnetic susceptibility scale using permanent magnets as far as we know. We also estimated major noise sources for a 0.1 mg silica mirror and found the noise level to be lower than the SQL at 400 Hz-18 kHz. In conclusion, the levitation system of a mg-scale mirror for the use in a macroscopic quantum measurement was realized.