一种基于介观孪生光束的四态量子通信协议
A four-state quantum communication protocol with mesoscopic twin beams
- University of Insubria（因苏布里亚大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究将基于孪生光束的量子通信协议扩展为四态编码，利用平均光子数和噪声抑制因子实现每使用传输两比特，并通过实验验证了其安全性和抗截获-重发攻击能力。
AI中文摘要：
由参量下转换产生的孪生光束（TWB）态展现出强的光子数关联，这种关联可被用于量子通信。在介观区域，这些关联可直接利用光子数分辨探测器（如硅光电倍增管（SiPMs））进行研究。其非经典性质通过噪声抑制因子（NRF）量化，该因子提供了量子关联的见证，并作为监测信道安全性的手段。在本工作中，一种基于TWB态、最初为二进制编码提出的量子通信协议被扩展为四态方案，该方案每次使用能够传输两个比特。信息通过将两个平均光子数值和叠加在孪生光束一个臂上的热噪声的两个模式数相结合来编码，在(m,R)平面中定义了四个可区分的状态。虽然平均探测光子数能够检索一个比特，NRF则提供第二个比特的区分，并作为对抗截获-重发攻击的安全检查，此类攻击会引入额外噪声并降低量子关联。该协议通过两个实验测量活动进行研究。首先，对孪生光束源在光子数统计、NRF和探测效率方面进行表征，以确定通信信道的运行条件。随后，实施四态协议，并通过状态分布及其95%置信区域的分析、作为样本大小函数的错误概率，以及用于状态区分的机器学习分类器的比较评估来评价该协议。最后，研究了NRF对截获-重发攻击的响应，以评估协议检测窃听的能力。
英文摘要：
Twin-beam (TWB) states generated by parametric down-conversion exhibit strong photon-number correlations that can be exploited for quantum communication. In the mesoscopic regime, these correlations can be directly investigated using photon-number-resolving detectors, such as silicon photomultipliers (SiPMs). Their nonclassical nature is quantified by the noise reduction factor (NRF), which provides a witness of quantum correlations and a means of monitoring channel security. In this work, a quantum communication protocol based on TWB states, originally proposed for binary encoding, is extended to a four-state scheme capable of transmitting two bits per use. Information is encoded by combining two mean photon-number values and two mode numbers of thermal noise superimposed on one arm of the twin beam, defining four distinguishable states in the (m,R) plane. While the mean detected photon number enables the retrieval of one bit, the NRF provides discrimination of the second bit and a security check against intercept-and-resend attacks, which introduce additional noise and degrade the quantum correlations. The protocol is investigated through two experimental measurement campaigns. First, the twin-beam source is characterized in terms of photon-number statistics, NRF, and detection efficiency to establish the operating conditions of the communication channel. Subsequently, the four-state protocol is implemented and evaluated through the analysis of state distributions and their 95% confidence regions, error probability as a function of sample size, and a comparative assessment of machine learning classifiers for state discrimination. Finally, the response of the NRF to an intercept-and-resend attack is investigated to assess the protocol's ability to detect eavesdropping.
