Detection of Unknown RF Signals Using Rydberg-Atom Quantum MIMO Receivers

Rydberg-atom quantum receivers (RAQRs) enable ultra-sensitive radio frequency (RF) detection by transducing incident fields into the optical domain with minimal quantum noise. This letter addresses the unexplored problem of detecting unknown RF signal presence under noise by formulating it as a binary hypothesis test for MIMO RAQRs with nonlinear magnitude-only measurements. We derive likelihood ratio tests (LRTs) under varying channel and signal knowledge, and propose a non-coherent constant false alarm rate (CFAR) energy detector for fully unknown scenarios. We analyze the role of reference signals, showing that excessive reference power can impair detection. Simulations demonstrate superior performance of the proposed RAQR over RF receiver.