Generating and Characterizing GHZ State Using Time-bin Qubits

Quantum entanglement is the cornerstone of many algorithms that hold the promise of solving significant classically-intractable problems. While many qubit platforms have demonstrated high coherence times and gate fidelity, photonic qubits are a natural choice for quantum networks due to their low-propagation noise at room temperature. In this work, we present an experimental demonstration of time-bin GHZ that is suitable for quantum communication and also interfacing with other entanglement-based networks. The time-bin GHZ states are generated by interfering a time-bin qubit with one of the members of a time-bin entangled Bell state on a 2x2 switch. Post selection of the photons exiting the two output ports projects the state onto a time-bin GHZ state. We support our experimental results with a characteristic function based theoretical model.