Near-deterministic Bell measurement for multiphoton quantum information processing

We propose a Bell measurement scheme for discriminating logical Bell states with many photons. The logical qubit is in Greenberger-Horne-Zeilinger entanglement with an arbitrary number of photons. Remarkably, its success probability can be made arbitrarily high using only linear optics and photon on-off measurements as the number of photons increases. It is shown that our scheme outperforms all the previously known schemes using single-photon qubits with respect to both the efficiency and feasibility. Our proposal provides an alternative candidate for all-optical quantum information processing.