Speaker
Description
Vacuum magnetic birefringence is a QED prediction in which a magnetic field makes the vacuum optically anisotropic. The expected birefringence is extremely small, approximately $4 \times 10^{-24} ~[\mathrm{T}^{-2}] \cdot B^2$, and has not yet been directly measured. A major limitation of cavity enhanced polarimetry is intrinsic birefringence noise, likely dominated by thermal fluctuations in the cavity mirror coatings, which decreases with increasing signal frequency. We present a prototype Fabry-Perot polarimeter utilizing magnetically levitated dipole magnets rotating at high frequency in vacuum. An active magnetic bearing concept aims to suppress mechanical vibration while allowing rotation frequencies up to $500 ~\mathrm{Hz}$, with the vacuum magnetic birefringence signal appearing at twice the rotation frequency. This approach shifts the measurement to a lower noise spectral region and provides a path toward improved sensitivity in laboratory searches for vacuum magnetic birefringence.
| Primary Abstract Topic | Experiment: Other Dark Matter |
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