Data from: Approaching the standard quantum limit of a Rydberg-atom microwave electrometer

The development of a microwave electrometer with inherent uncertainty
approaching its ultimate limit carries both fundamental and technological
significance. However, due to the thermal motion of atoms, the
state-of-the-art Rydberg electrometer falls considerably short of the
standard quantum limit by about three orders of magnitude. Here, we
utilize an optically thin medium with approximately 5.2×105 laser-cooled
atoms to implement the microwave heterodyne detection. By mitigating
various noises and strategically optimizing the electrometer parameters,
our study reduces the equivalent noise temperature by a factor of 20 and
achieves an electric-field sensitivity of 10.0nVcm-1Hz-1/2, finally
reaching a factor of 2.6 above the standard quantum limit. Our work also
provides valuable insights into the inherent capabilities and limitations
of Rydberg electrometers, offering superior sensitivity in detecting weak
microwave signals for numerous applications.