Enhancing the Sensitivity of Atom-Based Microwave-Field Electrometry Using a Mach-Zehnder Interferometer

We demonstrate the sensitivity enhancement of measurement of microwave electric fields by use of the full information of the complex atomic susceptibility. The transfer characteristics of both the microwave electric fields and the noise relevant to atoms, which are mapped to two quadrature components of the probe light, are systematically measured with use of a Mach-Zehnder interferometer. On the basis of the readout of the full complex atomic susceptibility, a sensitivity enhancement of 12 dB is achieved when the probe light has red detuning of 6 MHz. The results shed light on increasing the sensitivity of atomic sensors of microwave electric fields that is beyond the capability of the traditional antenna.