Harnessing multi-level electron transitions, Rydberg Atomic REceivers (RAREs) can detect wireless signals across a wide range of frequency bands, from Megahertz to Terahertz. This capability enables multi-band wireless communications and sensing (CommunSense). Existing research on multi-band RAREs primarily focuses on experimental demonstrations, lacking a tractable model to mathematically characterize their mechanisms. This issue leaves the multi-band RARE as a black box and poses challenges in its practical applications. To fill in this gap, this paper investigates the underlying mechanism of multiband RAREs and explores their optimal performance. For the first time, an analytical transfer function with a closed-form expression for multi-band RAREs is derived by solving the quantum response of Rydberg atoms. It shows that a multiband RARE simultaneously serves as 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 intrinsic gain 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 CommunSense performance. An experiment platform is built to validate the effectiveness of the derived transfer function, and numerical results confirm the superiority of multi-band RAREs.

翻译：利用多能级电子跃迁，里德堡原子接收器（RAREs）能够检测从兆赫兹到太赫兹的宽频段无线信号。这一能力实现了多频段无线通信与感知（CommunSense）。现有关于多频段RAREs的研究主要集中于实验演示，缺乏可处理的数学模型来刻画其工作机制。这一问题使得多频段RARE如同黑箱，为其实际应用带来了挑战。为填补这一空白，本文研究了多频段RAREs的内在机制并探索了其最优性能。通过求解里德堡原子的量子响应，首次推导出具有闭式表达式的多频段RAREs解析传递函数。研究表明，多频段RARE同时充当多频段原子混频器（用于下变频多频段信号）和多频段原子放大器（反映其对各频段的灵敏度）。对原子放大器的进一步分析揭示，各频段的固有增益可解耦为全局增益项和拉比注意力项。前者决定RARE对所有无线信号频段的整体灵敏度，后者影响整体灵敏度在各频段的分配，体现了多频段RAREs独特的注意力机制。本文提供了全局增益的最优设计以最大化多频段RAREs的整体灵敏度。随后，推导出最优拉比注意力以最大化实际多频段CommunSense性能。搭建了实验平台以验证所推导传递函数的有效性，数值结果证实了多频段RAREs的优越性。