Distributed Quantum Computing with Photons and Atomic Memories

We propose a universal quantum computing scheme that harnesses photonic polarizations and atomic-ensemble ground-state quantum memories (QM). This photon-atom hybrid platform could allow modular quantum computing connectivity that circumvents probabilistic nature of entanglement with a deterministic one. Our approach achieves high storage-retrieval efficiency by converting photonic polarization states into efficient atomic-ensemble-based QM states. We present two CP gate configurations using Rydberg blockade approach: one employing dual QM atomic ensembles in close proximity with overlapping photon modes, and the other using a single ensemble accommodating two spatially overlapping photonic modes. Our analysis and simulations indicate that while QM loss primarily affects state generation efficiency, it has minimal impact on fidelity. The scalability of our method is demonstrated through its extension to the generation of N-photon Greenberger-Horne-Zeilinger (GHZ) states. We discuss the potential of our scheme for spatially and temporally distributed quantum computing, emphasizing its role as a quantum network interface that bridges flying photons with stationary atomic nodes.