  The promise of universal quantum computing requires scalable single- and
inter-qubit control interactions. Currently, three of the leading candidate
platforms for quantum computing are based on superconducting circuits, trapped
ions, and neutral atom arrays. However, these systems have strong interaction
with environmental and control noises that introduce decoherence of qubit
states and gate operations. Alternatively, photons are well decoupled from the
environment, and have advantages of speed and timing for distributed quantum
computing. Photonic systems have already demonstrated capability for solving
specific intractable problems like Boson sampling, but face challenges for
practically scalable universal quantum computing solutions because it is
extremely difficult for a single photon to "talk" to another deterministically.
Here, we propose a universal distributed quantum computing scheme based on
photons and atomic-ensemble-based quantum memories. Taking the established
photonic advantages, we mediate two-qubit nonlinear interaction by converting
photonic qubits into quantum memory states and employing Rydberg blockade for
controlled gate operation. We further demonstrate spatial and temporal
scalability of this scheme. Our results show photon-atom network hybrid
approach can be an alternative solution to universal quantum computing.
