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 printed circuit board (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 210 MHz to 308.6 MHz band with a relative bandwidth of 38<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> and the enhancement factor ranging from 38 dB to 47 dB. By adjusting the height of the CTER, different sizes of atomic vapor cells can be accommodated while maintaining good enhancement. In the <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small>-resonant region, the detective sensitivity of the RAR with and without CTER at 223.7 MHz were measured at 179.37 nV <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\cdot {\text{cm}}^{-1}$</tex-math></inline-formula><inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \cdot {\text{Hz}}^{-1/2}$</tex-math></inline-formula> and 40.16 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula>V<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\cdot$</tex-math></inline-formula><inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\text{cm}^{-1}$</tex-math></inline-formula><inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$ \cdot {\text{Hz}}^{-1/2}$</tex-math></inline-formula> by utilizing the Rydberg atomic heterodyne technique, respectively. Furthermore, the CTER displays a compact electrical size, approximately 3.37× 10<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{-5}$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda ^{3}$</tex-math></inline-formula> 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.