Parity measurement of remote qubits using dispersive coupling and photodetection

Parity measurement is a key step in many entanglement generation and quantum error correction schemes. We propose a protocol for nondestructive parity measurement of two remote qubits, i.e., macroscopically separated qubits with no direct interaction. The qubits are instead dispersively coupled to separate resonators that radiate to shared photodetectors. The scheme is deterministic in the sense that there is no fundamental upper bound on the success probability. In contrast to previous proposals, our protocol addresses the scenario where number-resolving photodetectors are available but the qubit-resonator coupling is time independent and only dispersive.