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Experimental entanglement swapping through single-photon χ(2) nonlinearity

Author

Listed:
  • Yoshiaki Tsujimoto

    (National Institute of Information and Communications Technology (NICT))

  • Kentaro Wakui

    (National Institute of Information and Communications Technology (NICT))

  • Tadashi Kishimoto

    (National Institute of Information and Communications Technology (NICT))

  • Shigehito Miki

    (National Institute of Information and Communications Technology (NICT))

  • Masahiro Yabuno

    (National Institute of Information and Communications Technology (NICT))

  • Hirotaka Terai

    (National Institute of Information and Communications Technology (NICT)
    National Institute of Information and Communications Technology (NICT))

  • Mikio Fujiwara

    (National Institute of Information and Communications Technology (NICT))

  • Go Kato

    (National Institute of Information and Communications Technology (NICT))

Abstract

In photonic quantum information processing, quantum operations using nonlinear photon-photon interactions are vital for implementing two-qubit gates and enabling faithful entanglement swapping. However, due to the weak interaction between single photons, the all-photonic realization of such quantum operations has remained out of reach so far. Herein, we demonstrate an entanglement swapping using sum-frequency generation between single photons in a χ(2)-nonlinear optical waveguide. We show that a high signal-to-noise ratio (SNR), stable sum-frequency-generation-based entanglement heralder with an ultralow-dark-count superconducting single-photon detector can satisfy the unprecedented SNR requirement indispensable for the swapping protocol. Furthermore, the system clock is enhanced by utilizing ultrafast telecom entangled photon-pair sources that operate in the GHz range. Our results confirm a lower bound 0.770(76) for the swapped state’s fidelity, surpassing the classical limit of 0.5 successfully. Our findings highlight the strong potential of broadband all-single-photonic nonlinear interactions for further sophistication in long-distance quantum communication and photonic quantum computation.

Suggested Citation

  • Yoshiaki Tsujimoto & Kentaro Wakui & Tadashi Kishimoto & Shigehito Miki & Masahiro Yabuno & Hirotaka Terai & Mikio Fujiwara & Go Kato, 2025. "Experimental entanglement swapping through single-photon χ(2) nonlinearity," Nature Communications, Nature, vol. 16(1), pages 1-8, December.
    • Handle: RePEc:nat:natcom:v:16:y:2025:i:1:d:10.1038_s41467-025-63785-5
    DOI: 10.1038/s41467-025-63785-5
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