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

delete2025-10-07
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OA
AI
Y
Yoshiaki Tsujimoto *
K
Kentaro Wakui
T
Tadashi Kishimoto
S
Shigehito Miki
M
Masahiro Yabuno
H
Hirotaka Terai
M
Mikio Fujiwara
G
Go Kato
DOI：10.1038/s41467-025-63785-5delete
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Abstract

Abstract

En 中文
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. Nonlinear optical interactions could in principle allow simpler implementations of quantum information processing, compared to linear-optics-based ones, but the task is hindered by the weak nature of the interaction. Here, the authors demonstrate quantum teleportation and entanglement swapping using the parametric nonlinear process of sum-frequency generation.
Keywords:
entanglement swapping
sum-frequency generation
single-photon nonlinearity
quantum information processing
χ(2)-nonlinear optical waveguide
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Journal

Nature Communications cover
Nature Communications
IF:
15.7
Papers:
9.2W
Citations:
91.2W

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