Quantum Process Tomography of a Controlled-Phase Gate for Time-Bin Qubits

Hsin Pin Lo, Takuya Ikuta, Nobuyuki Matsuda, Toshimori Honjo, William J. Munro, Hiroki Takesue

Research output: Contribution to journalArticlepeer-review

9 Citations (Scopus)


Time-bin qubits, where information is encoded in a single photon at different times, have been widely used in optical-fiber- A nd waveguide-based quantum communications. With the recent developments in distributed quantum computation, it is logical to ask whether time-bin encoded qubits may be useful in that context. We have recently realized a time-bin qubit controlled-phase (C-phase) gate using a 2×2 optical switch based on a lithium-niobate waveguide, with which we demonstrated the generation of an entangled state. However, the experiment was performed with only a pair of input states and thus the functionality of the C-phase gate was not fully verified. In this research, we use quantum process tomography to establish a process fidelity of 97.1%. Furthermore, we demonstrate the controlled-not gate operation with a process fidelity greater than 94%. This study confirms that typical two-qubit logic gates used in quantum computational circuits can be implemented with time-bin qubits and thus it is a significant step forward for the realization of distributed quantum computation based on time-bin qubits.

Original languageEnglish
Article number034013
JournalPhysical Review Applied
Issue number3
Publication statusPublished - 2020 Feb
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)


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