Boosting single-photon Bell-state measurement with deterministic ancillae

Bell-state measurements underpin quantum teleportation, quantum repeaters, modular quantum computing, and fusion-based quantum computing. Its linear-optical implementation is known to succeed with a maximum 50% probability for single-photon qubits. This limit could be surpassed by introducing auxiliary photons, but existing proposals employ photonic states that are expensive and probabilistic to generate. In this work, we show that single-photon Bell-state measurement successful rate can be enhanced by utilizing squeezed-vacuum ancillae, which can be deterministically prepared in most photonic platforms. Our scheme achieves 58.3% successful rate with about 6.38 dB squeezing for double-rail encoding and 54.7% with about 6.27 dB for single-rail encoding. Our scheme can also improve the success probability of ambiguous state discrimination. Our result offers a practical route to improve the efficiency of photonic quantum information processing.