Twin-field (TF) quantum key distribution (QKD) has rapidly risen as the most viable solution to long-distance secure fibre communication thanks to its fundamentally repeater-like rate-loss scaling. However, its implementation complexity, if not successfully addressed, could impede or even prevent its advance into real-world. To satisfy its requirement for twin-field coherence, all present setups adopted essentially a gigantic, resource-inefficient interferometer structure that lacks scalability that mature QKD systems provide with simplex quantum links. Here we introduce a technique that can stabilise an open channel without using a closed interferometer and has general applicability to phase-sensitive quantum communications. Using locally generated frequency combs to establish mutual coherence, we develop a simple and versatile TF-QKD setup that does not need service fibre and can operate over links of 100 km asymmetry. We confirm the setup’s repeater-like behaviour and obtain a finite-size rate of 0.32 bit/s at a distance of 615.6 km.
We develop a novel technique to stabilize an open channel without using frequency dissemination for twin-field quantum key distribution. A versatile setup is demonstrated at a distance of 615.6 km, achieving the repeater-like behaviour.
We achieve a finite-size key rate of 42.64bps over 508km fibers, breaking the fundamental rate-loss limit of point-point quantum key distribution (QKD), via implementing an innovative measurement-device-independent QKD through asynchronous coincidence pairing.
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