RIS-Assisted Atomic MIMO Receiver

In this paper, we propose a novel and low-complexity atomic multiple-input multiple-output (MIMO) receiver architecture assisted by a reconfigurable intelligent surface (RIS). By introducing RIS and utilizing pulse amplitude modulation (PAM), the phase of the transmitted signal is effectively aligned with that of the local oscillator (LO), mitigating phase ambiguity and reducing the complexity of the receiver. To tackle the resulting non-convex optimization problem, we reformulate it into a tractable form by minimizing the Frobenius norm of an equivalent matrix, which is solved using an Adam-based gradient descent algorithm. Building upon the optimized equivalent signals, we develop a low-complexity signal detection algorithm and evaluate its performance. Simulation results demonstrate that the proposed RIS-assisted atomic MIMO receiver significantly enhances detection performance compared to the conventional atomic MIMO receivers. More importantly, these results underscore the proposed architecture's potential for scalable and high-performance atomic MIMO communication systems.