Twin-field quantum key distribution can overcome the repeaterless bound via single-photon interference. However, the requirements of phase-locking and phase-tracking techniques drastically increase the experimental complexity, economic cost and prohibit free-space realization. Inspired by the duality in entanglement, we herein present an asynchronous measurement-device-independent quantum key distribution protocol that can surpass the repeaterless bound even without phase locking and phase tracking. Leveraging the concept of time multiplexing, asynchronous two-photon Bell-state measurement is realized by postmatching two interference detection events. For a 1 GHz system, the new protocol reaches a transmission distance of 450 km without phase tracking. After further removing phase locking, our protocol is still capable of breaking the bound at 270 km by employing a 10 GHz system. Intriguingly, when using the same experimental techniques, our protocol has a higher key rate than the phase-matching-type twin-field protocol. In the presence of imperfect intensity modulation, it also has a significant advantage in terms of the transmission distance over the sending-or-not-sending type twin-field protocol. With high key rates and accessible technology, our work paves the way for realistic global quantum networks across space, air, and water to the ground.
翻译:双野量子钥匙分配可以通过单发磷干扰来克服无中继器的无中继器约束。然而,分阶段锁定和分阶段跟踪技术的要求大大增加了实验的复杂性、经济成本和禁止自由空间的实现。在纠缠的双重性激励下,我们在此提出一个非同步的测量-偏离独立量子钥匙分配协议,即使没有阶段锁定和阶段跟踪,也能够超过无中继器约束,即使没有阶段锁定和阶段跟踪,也能够超过无中继器约束的无中继器约束。利用时间多重式概念,不同步的二发磷贝尔-状态测量是通过对两次干扰探测事件的匹配来实现的。对于1 GHz系统来说,新协议的传输距离达到450公里,而没有阶段跟踪。在进一步去除阶段锁定后,我们的协议仍然能够突破270公里的界限。 奇怪的是,在使用同样的实验技术时,我们的协议的关键速度比相配型双场双场协议要高。在存在不完善的强度调制中,它也具有显著的优势。对于1GHZ系统而言,传送距离为450公里的传输距离,而不能跟踪。在高空基地轨道上,并且可以进入全球空间协议。