Quantum communication with time-bin qubits

Time-bin qubits are an ideal encoding to perform various optical fiber-based quantum communications operations including quantum key distribution. In this talk, I will introduce time-bin qubits-based quantum information processing experiments utilizing a high-speed two-input, two-output (2x2) optical switch [1]. We have demonstrated time-bin qubit quantum logic gates [2] and characterized their operation using quantum process tomography [3]. Further, we have recently generated three-photon time-bin GHZ states [4] by entangling an entangled photon pair from an SPDC photon pair and a single time-bin photon from a weak coherent pulse. Based on these results, we anticipate that time-bin qubits will be an ideal resource for the realization of a future quantum internet.
 
References:
1. H. Takesue, Entangling time-bin qubits with a switch, Phys. Rev. A 89, 062328 (2014).
2. H. P. Lo, T. Ikuta, N. Matsuda, T. Honjo, and H. Takesue, Entanglement generation using a controlled-phase gate for time-bin qubits, Appl. Phys. Exp. 11, 092801 (2018).
3. H. P. Lo, T. Ikuta, N. Matsuda, T. Honjo, W. J. Munro, and H. Takesue, Quantum Process Tomography of a Controlled-Phase Gate for Time-Bin Qubits, Phys. Rev. Appl. 13, 034013 (2020).
4. H. P. Lo, T. Ikuta, K. Azuma, T. Honjo, W. J. Munro, and H. Takesue, Generation of a time-bin Greenberger–Horne–Zeilinger state with an optical switch, Quantum Sci. Technol. 8, 035003 (2023).