Multi-parameter microwave quantum sensing with a single atomic probe

We demonstrate a multi-parameter sensing scheme for free space microwave electric and magnetic fields in single vapor cell based on the atom-based microwave detection techniques. A weak probe laser though a rubidium vapor cell first acts as magnetic probe to measure the microwave magnetic field via atomic Rabi resonance of the ground state hyperfine transition. When another strong coupling laser is subsequently counter-propagated and overlapped with the probe laser in the same atomic vapor cell, the probe laser is then used as electric probe to measure microwave electric field by off-resonant microwave dressed Rydberg Autler-Townes splitting. We achieve measurement of microwave electric and magnetic fields without any complicated tuning methods at the clock frequency of 6.835 GHz. Based on the inherent relationship between microwave electric and magnetic fields, and their good linear response characteristics in respective suitable power ranges, the equivalent microwave magnetic fields are derived from linear fitting of the measured electric fields, which are in agreement with the calibrated experimental results within the same power range. This work provides an effective approach for extending the power dynamic range of atom-based microwave quantum sensors.