Bridging gaps in Rydberg RF receivers using modulation transfer bandwidth enhancement

TL;DR

This paper enhances the bandwidth of quantum Rydberg atom RF receivers by optimizing modulation parameters, enabling detection of signals detuned by several MHz and bridging large transition gaps.

Contribution

It introduces a theoretical and experimental optimization of modulation transfer protocol to significantly extend the detection bandwidth of Rydberg RF receivers.

Findings

Optimized modulation parameters increase detection bandwidth.

The protocol outperforms conventional methods for detuned RF signals.

Experimentally bridged a 166 MHz gap between Rydberg transitions.

Abstract

We optimize theoretically and experimentally the performances of the recently demonstrated modulation transfer protocol [D.-A. Trinh, K. V. Adwaith, M. Branco, A. Rouxel, S. Welinski, P. Berger, F. Goldfarb, and F. Bretenaker, Applied Physics Letters 125, 154001 (2024)] aiming at extending the bandwidth of quantum RF receivers based on hot Rydberg atoms. This optimization relies on tuning the parameters of the phase modulation of the coupling beam, which is converted by the nonlinear response of the atoms into an amplitude modulation of the probe beam. We develop a theoretical model to optimize both the modulation frequency and the modulation amplitude of the coupling beam, thereby maximizing the atomic response. Once optimized, the sensitivity to detuned RF fields of this modulation transfer protocol is measured and compared with that of the conventional protocol. This comparison shows that the new protocol permits a strong increase in the detection bandwidth. Indeed, it outperforms the usual one as soon as the RF signal to be measured is detuned by more than a few MHz. We illustrate the capability of this modulation transfer protocol to enhance the detection bandwidth by showing experimentally how it permits to bridge the gap between two Rydberg transitions separated by 166 MHz. In all cases, the experimental results are in good agreement with the simulations.