Abstract: Based on the coupling system of trapped atoms and a single-sided optical microcavity, we propose an entanglement measurement scheme for nonlocal two-qubit photonic entangled states in this work. By utilizing photon-atom interactions during the input-output process of photons, direct measurement of entanglement concurrence is achieved for Bell states, arbitrary two-qubit entangled pure states, and Collins-Gisin states. By establishing an analytic correspondence between the concurrence of nonlocal photonic entanglement and the probability of atomic state projection measurement, nondemolition measurement of nonlocal photonic entanglement is realized, while allowing the photonic entangled state to evolve into the nonlocal maximally entangled state. Crucially, the proposed scheme is not limited by high-Q cavities or strong-coupling mechanisms and can function effectively under low-Q cavities and weak-coupling conditions, thereby significantly reducing experimental difficulty.

Key words: quantum information, entanglement measurement, entanglement concurrence, cavity quantum electrodynamics