Wideband Quantum Transduction for Rydberg Atomic Receivers Using Six-Wave Mixing
This paper investigates a six-wave mixing (SWM)-based Rydberg atomic receiver as a wideband radio frequency (RF)-to-optical quantum transducer. Specifically, we develop an explicit baseband input-output model that bridges the RF-induced atomic coherence to the detected optical readout. Based on the exact detected SWM response, we develop a reduced-order closed-form two-pole low-pass approximation under the near-resonant weak-signal of interest, which provides an analytical insight into how the 3-dB bandwidth is manipulated by the dressed higher-level atomic dynamics and optical/RF parameters. The validity range of this approximation is then quantified to clarify the operating conditions under which this reduced-order model accurately represents the exact SWM response. We further characterize the linear dynamic range by employing the 1-dB compression point (P1dB) and the input-referred third-order intercept point (IIP3), unveiling a communication-compatible characterization of the bandwidth-sensitivity-linearity trade-off. Extensive simulation results demonstrate that SWM can achieve a 3-dB bandwidth of approximately 10 MHz while maintaining favorable linearity and sensitivity under the strict low-pass condition. The comparison with the EIT regime indicates that the two schemes should be treated as complementary rather than universally ordered. From an engineering perspective, the preferred SWM operating region is therefore not the one with the largest bandwidth, but the one that simultaneously provides a large bandwidth, acceptable sensitivity, favorable linearity, and low-pass regularity.