Rydberg Atomic Receivers for Multi-Band Communications and Sensing

Harnessing multi-level electron transitions, Rydberg Atomic Receivers (RAREs) can detect wireless signals across a wide range of frequency bands, from Megahertz to Terahertz, enabling multi-band communications and sensing (C&S). Current research on multi-band RAREs primarily focuses on experimental demonstrations, lacking an interpretable model to mathematically characterize their mechanisms. This issue leaves the multi-band RARE as a black box, posing challenges in its practical C&S applications. To fill in this gap, this paper investigates the underlying mechanism of multi-band RAREs and explores their optimal performance. For the first time, the closed-form expression of the transfer function of a multi-band RARE is derived by solving the quantum response of Rydberg atoms excited by multi-band signals. The function reveals that a multiband RARE simultaneously serves as both a multi-band atomic mixer for down-converting multi-band signals and a multi-band atomic amplifier that reflects its sensitivity to each band. Further analysis of the atomic amplifier unveils that the gain factor at each frequency band can be decoupled into a global gain term and a Rabi attention term. The former determines the overall sensitivity of a RARE to all frequency bands of wireless signals. The latter influences the allocation of the overall sensitivity to each frequency band, representing a unique attention mechanism of multi-band RAREs. The optimal design of the global gain is provided to maximize the overall sensitivity of multi-band RAREs. Subsequently, the optimal Rabi attentions are also derived to maximize the practical multi-band C&S performance. Numerical results confirm the effectiveness of the derived transfer function and the superiority of multi-band RAREs.