Robust-fidelity atom-photon entangling gates in the weak-coupling regime

Abstract

We describe a simple entangling principle based on the scattering of photons off single emitters in one-dimensional waveguides (or extremely-lossy cavities). The scheme can be applied to photonic qubits encoded in polarization or time-bin, and features a filtering mechanism that works effectively as a built-in error-correction directive. This automatically maps imperfections from weak couplings, atomic decay into undesired modes, frequency mismatches, or finite bandwidths of the incident photonic pulses, into heralded losses instead of infidelities. The scheme is thus adequate for high-fidelity maximally entangling gates even in the weak-coupling regime. These, in turn, can be directly applied to store and retrieve photonic-qubit states, thereby completing an atom-photon interface toolbox, or to sequential measurement-based quantum computations with atomic memories.