Quantum communication complexity studies the efficiency of information communication (that is, the minimum amount of communication required to achieve a certain task) using quantum states. One representative example is quantum fingerprinting, in which the simultaneous message passing model is considered and the minimum amount of communication could be exponentially smaller than the classical fingerprinting protocol. Experimental demonstrations based on a practical quantum fingerprinting protocol where coherent states are used to construct the fingerprints, have successfully shown the superiority of quantum fingerprinting. However, as a consequence of using coherent states, the communication time in this coherent quantum fingerprinting (CQF) protocol is increased. Moreover, the minimum amount of information communicated in these experimental demonstrations is largely limited by the dark counts of the single photon detectors. Here, we propose to enhance the performance of the existing CQF protocol through applying wavelength division multiplexing (WDM) and simultaneous detection of multiple wavelength channels. We show that the new WDM-CQF protocol can potentially reduce the communication time significantly. More importantly, with the same experimental parameters, the amount of communication is much reduced in the new scheme compared with the original CQF protocol. The more wavelength channels are used, the less communication is required by WDM-CQF protocol. We also perform a proof-of-concept experimental demonstration of the new WDM-CQF protocol with 6 wavelength channels. The experimental results further validate that the new scheme with WDM not only beats the classical protocol, but also reduces the amount of communication required by the original CQF protocol by more than half.
A theoretical study of subcarrier-wave quantum key distribution system integration with an optical transport network utilizing dense wavelength division multiplexing
ITMO University（ITMO大学）；Leading Research Center ‘National Center of Quantum Internet’, ITMO University（ITMO大学领先研究中心‘国家量子互联网中心’）；Quanttelecom LLC.（Quanttelecom有限责任公司）
Self-testing mutually unbiased bases in higher dimensions with space-division multiplexing optical fiber technology
在设备无关的量子信息方法中，给定任务的实现可以仅从记录的统计数据进行自测试，而无需所采用设备的详细模型。尽管实验要求很高，但它为自然满足相关要求的先进量子技术提供了有吸引力的验证方案。在这项工作中，我们实验研究是否可以采用自测试协议来证明现代空分复用光纤技术构建的新量子设备的正常运行。具体地，我们考虑了M.~法卡斯和J.~ Kaniewski（Phys.~修订版~ A 99，032316），用于对应于维度$d>2$中的互无偏基（MUB）的自测试测量。在我们的方案中，状态准备和测量阶段的实施与新的多芯光纤和相关组件构建的多臂干涉仪。由于该技术实现的干涉仪的光学模式的高度重叠，我们能够达到用于自测试两个四维MUB的实现所需的频率。我们还量化了测量的两个操作量：（i）与Bell违规相关的不兼容性鲁棒性，以及（ii）从结果中提取的随机性。由于MUB位于几个量子信息协议的核心，我们的研究结果对未来依赖于空分复用光纤的量子工程具有实际意义。
