Optimal feedback for remote entanglement*

Recent experiments in superconducting qubits have demonstrated measurement as a resource for entanglement, even when qubits are spatially separated to a significant degree. We consider the problem of using measurement combined with feedback to deterministically entangle remote qubits. This constraint forces us to consider only local feedback, which leads us to an interesting control-theory problem. Within this constraint, we derive a series of protocols for this system which generate entanglement as quickly as possible. We find that even in the presence of expected experimental imperfections, it should be possible to achieve high-fidelity entanglement with currently accessible experimental parameters.