Performance of Antenna-based and Rydberg Quantum RF Sensors in the Electrically Small Regime

TL;DR

This paper compares the sensitivity of Rydberg atom RF sensors and small antennas, finding that current Rydberg sensors are less sensitive than antennas but could outperform them under ideal quantum-limited conditions.

Contribution

It provides a comparative analysis of Rydberg sensors and small antennas, including circuit models and sensitivity calculations, highlighting potential advantages of quantum sensors at the quantum limit.

Findings

Current Rydberg sensors are less sensitive than active antennas.

Ideal Rydberg sensors at the quantum limit could surpass antenna sensitivity.

Both sensor types operate below atmospheric noise levels.

Abstract

Rydberg atom electric field sensors are tunable quantum sensors that can perform sensitive radio frequency (RF) measurements. Their qualities have piqued interest at longer wavelengths where their small size compares favorably to impedance-matched antennas. Here, we compare the signal detection sensitivity of cm-scale Rydberg sensors to similarly sized room-temperature electrically small antennas with active and passive receiver backends. We present and analyze effective circuit models for each sensor type, facilitating a fair sensitivity comparison for cm-scale sensors. We calculate that contemporary Rydberg sensor implementations are less sensitive than unmatched antennas with active amplification. However, we find that idealized Rydberg sensors operating with a maximized atom number and at the standard quantum limit may perform well beyond the capabilities of antenna-based sensors at room temperature, the sensitivities of both lying below typical atmospheric background noise.