Continuously Expanding the Response Frequency of Rydberg Atom-Based Microwave Sensor by Using Quantum Mixer

TL;DR

This paper introduces a method to significantly extend the response frequency range of Rydberg atom-based microwave sensors using a quantum mixer and heterodyne technology, achieving broad bandwidth with high sensitivity.

Contribution

The authors develop a novel approach combining a controlled driving field and quantum mixing to expand the operational frequency range of Rydberg sensors beyond 1 GHz with minimal sensitivity loss.

Findings

Extended response frequency range up to 2 GHz.

Sensitivity decline less than twice for far-detuned fields.

Enhanced sensitivity by increasing controlled field intensity and frequency.

Abstract

Microwave electric (MW) field measurements utilizing Rydberg atoms have witnessed significant advancements, achieving remarkable sensitivity, albeit limited to discrete MW frequencies resonant with Rydberg states. Recently, various continuous-frequency measurement schemes have emerged. However, when the MW detuning surpasses 1 GHz, the sensitivity degrades by over an order of magnitude compared to resonant measurements. In this paper, we successfully extend the response frequency range by harnessing a controlled driving field in conjunction with a quantum mixer and heterodyne technology, theoretically enabling infinite scalability. Notably, second-order effects stemming from quantum mixing necessitate careful consideration to ensure accurate electric field measurements. In addition, compared to resonant measurements, the sensitivity decline for far-detuned MW fields exceeding 1 GHz is less than twice, representing a significant improvement of several orders of magnitude over alternative schemes. Furthermore, the sensitivity of far-detuned MW fields can be efficiently enhanced by augmenting the intensity and frequency of the controlled field. For detunings ranging from 100 MHz to 2 GHz, we present optimal sensitivity values and the corresponding methods to achieve them. Our findings pave the way for Rydberg atom-based MW receivers characterized by both high sensitivity and an exceptionally broad bandwidth.