  We measured the vibration of a prototype superconducting magnetic bearing
(SMB) operating at liquid nitrogen temperature. This prototype system was
designed as a breadboard model for LiteBIRD low-frequency telescope (LFT)
polarization modulator unit. We set an upper limit of the vibration amplitude
at $36~\mathrm{\mu m}$ at the rotational synchronous frequency. During the
rotation, the amplitude of the magnetic field produced varies. From this setup,
we compute the static and AC amplitude of the magnetic fields produced by the
SMB magnet at the location of the LFT focal plane as $0.24~\mathrm{G}$ and
$3\times10^{-5}$$~\mathrm{G}$, respectively. From the AC amplitude, we compute
TES critical temperature variation of $7\times10^{-8}$$~\mathrm{K}$ and
fractional change of the SQUID flux is $\delta
\Phi/\Phi_0|_{ac}=3.1\times10^{-5}$. The mechanical vibration can be also
estimated to be $3.6\times 10^{-2}$$~\mathrm{N}$ at the rotation mechanism
location.
