Loophole-free Bell-inequality violation between atomic states in cavity-QED systems mediated by hybrid atom–light entanglement

Abstract We present a feasible approach to testing Bell nonlocality and implementing device-independent quantum key distribution (DI) between distant atomic states in cavity-based architectures, mediated by hybrid atom–light entanglement. We develop a full theoretical model that incorporates realistic sources of noise—such as transmission loss, limited light–matter coupling efficiency, and imperfect detection. Our analysis shows that strong Bell–Clauser–Horne–Shimony–Holt violations and secure key generation over tens of kilometers are within reach using current or near-term technology. These results position cavity-based platforms with coherent-state encodings as a promising foundation for future DI quantum communication networks.