A Compact Tunable Enhancement Resonator for Rydberg Atomic Receiver

Rydberg atomic receivers (RARs) have emerged in the field of quantum precision measurement due to high sensitivity and self-calibration. In this letter, we demonstrate a compact tunable enhancement resonator (CTER) for enhancing the detective sensitivity of the RAR. The resonator consists of two PCB substrates and a copper tuning column, which achieves resonant frequency variation by continuously sliding the copper tuning column. During the measurement, we have achieved electric field enhancement in the 210MHz - 308.6MHz band with a relative bandwidth of 38\% and the enhancement factor ranging from 38dB to 47dB. By adjusting the height of the CTER, different sizes of atomic vapor cells can be accommodated while maintaining good enhancement. In the off-resonant region, the detective sensitivity of the RAR with and without CTER at 223.7MHz were measured at 179.37 nV \cdot {cm}^{-1} \cdot {Hz}^{-1/2} and 40.16\mu V\cdot\rm{cm}^{-1} \cdot {Hz}^{-1/2} by utilizing the Rydberg atomic heterodyne technique, respectively. Furthermore, the CTER displays a compact electrical size, approximately 3.37× ^{-5} \lambda ^{3} in comparison to other resonators, which facilitates the miniaturization and integration of the RAR. Its remarkable resonance characteristics and broadband tuning capability provide support for achieving high-sensitivity and broadband quantum microwave measurements.