We report our progress towards the first experimental d emonstration of three photon time-bin GHZ entangled states. We also develop a theoretical model based on phase-space techniques to support the experimental results.
Evaluation of the Greenberger-Horne-Zeilinger (GHZ) theory requires an entangled n-particle state with n>3. To date, experimental achievement of a suitable GHZ state has proved elusive. This paper presents an approach to generate a three-photon entangled state and presents the theory of its space-time structure. Since an accurate picture of the space-time structure is important in understanding the two-photon state, an accurate picture of the three-photon state should be equally important.
Abstract Multipartite entanglement is a critical resource in quantum information processing that exhibits much richer phenomenon and stronger correlations than in bipartite systems. This advantage is also reflected in its multi-user applications. Although many demonstrations have used photonic polarization qubits, polarization-mode dispersion confines the transmission of photonic polarization qubits through an optical fiber. Consequently, time–bin qubits have a particularly important role to play in quantum communication systems. Here, we generate a three-photon time–bin Greenberger–Horne–Zeilinger (GHZ) state using a 2 × 2 optical switch as a time-dependent beam splitter to entangle time–bin Bell states from a spontaneous parametric down-conversion source and a weak coherent pulse. To characterize the three-photon time–bin GHZ state, we performed measurement estimation, showed a violation of the Mermin inequality, and used quantum state tomography to fully reconstruct a density matrix, which shows a state fidelity exceeding 70%. We expect that our three-photon time–bin GHZ state can be used for long-distance multi-user quantum communication.