Maeda Kento, Sasaki Toshihiko, Koashi Masato
Photon Science Center, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
Department of Applied Physics, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-8656, Japan.
Nat Commun. 2019 Jul 17;10(1):3140. doi: 10.1038/s41467-019-11008-z.
Quantum key distribution (QKD) over a point-to-point link enables us to benefit from a genuine quantum effect even with conventional optics tools such as lasers and photon detectors, but its capacity is limited to a linear scaling of the repeaterless bound. Recently, twin-field (TF) QKD was conjectured to beat the limit by using an untrusted central station conducting a single-photon interference detection. So far, the effort to prove the conjecture was confined to the infinite key limit which neglected the time and cost for monitoring an adversary's act. Here we propose a variant of TF-type QKD protocol equipped with a simple methodology of monitoring to reduce its cost and provide an information-theoretic security proof applicable to finite communication time. We simulate the key rate to show that the protocol beats the linear bound in a reasonable running time of sending 10 pulses, which positively solves the conjecture.
通过点对点链路进行量子密钥分发（QKD），即使使用诸如激光器和光子探测器等传统光学工具，我们也能够受益于真正的量子效应，但其容量仅限于无中继限制的线性缩放。最近，有人推测双场（TF）QKD通过使用一个进行单光子干涉检测的不可信中心站来突破这一限制。到目前为止，证明该推测的努力仅限于无限密钥限制，而忽略了监测对手行为的时间和成本。在此，我们提出一种TF型QKD协议的变体，配备一种简单的监测方法以降低其成本，并提供适用于有限通信时间的信息理论安全性证明。我们模拟了密钥率，结果表明该协议在发送10个脉冲的合理运行时间内突破了线性限制，从而肯定地解决了该推测。
