Novel optical transceivers and signaling techniques for quantum communications

安全通信旨在允许不同方之间的保密通信，使得未经授权的一方无法访问消息的内容。 如果窃听者具有相当大的计算能力，经典的安全通信方案可以被破坏。相比之下，在量子安全通信中，也称为量子密钥分发（QKD），无论窃听者可用的计算能力如何，原则上都可以保证密钥的安全性。在经典通信中，通信双方不知道窃听者正在访问私人信息。例如，如果有人窃听电话线，通信将不受影响地进行。然而，在量子通信中，信息泄露给窃听者与通信双方之间的通信降级定量相关。 这是因为窃听者从量子信道中提取信息的任何行为都是一种测量形式，并且根据量子物理学，测量通常会修改被测系统的状态。在这个建议中，我们探索新的收发器和信令方案，以最大限度地提高密钥传输的速率。我们考虑两种类型的通道-光纤和自由空间光学。在我们的分析和仿真中，我们包括失真和信道引入的噪声，我们还介绍了数字均衡器，以减轻信道损伤。我们估计的比特错误率和相互之间的通信双方在窃听者的存在/不存在。一旦使用我们的模拟工具优化了参数，我们将在国际合作者的帮助下进行实验。预期的结果是（i）新型光收发器，以及（ii）将开发提供更长距离和/或更高安全性的新调制方案。加拿大的工业和国防组织从这项研究中受益，因为更高的密钥速率可能有助于打击黑客和网络欺诈。

Secure communication aims at allowing confidential communication between different parties such that an unauthorized party does not have access to the content of messages. The classical secure communication schemes can be broken if an eavesdropper has a substantial amount of computational power. In contrast, in quantum secure communication also known as quantum key distribution (QKD), the security of the key can in principle be guaranteed regardless of the computational power available to the eavesdropper. In classical communication, communicating parties are not aware that an eavesdropper is accessing private information. For example, if someone is tapping into a telephone line, the communication goes on unmodified. However, in quantum communication, the leakage of information to the eavesdropper is quantitatively related to the degradation of the communication between the communicating parties. This is because any action by which the eavesdropper extracts information out of the quantum channel is a form of measurement and according to quantum physics, measurement in general modifies the state of the measured system. In this proposal, we explore novel transceivers and signaling schemes to maximize the rate of secret key transmission. We consider two types of channels - fiber optic and free space optic. In our analysis and simulation, we include the distortions and noise introduced by the channels and we also introduce digital equalizers to mitigate the channel impairments. We estimate the bit error rate and mutual information between the communicating parties in the presence/absence of the eavesdropper. Once the parameters are optimized using our simulation tools, experiments will be carried out with the help of our international collaborator. The expected outcomes are (i) novel optical transceivers, and (ii) new modulation schemes that provide longer distances and/or higher security will be developed. The Canadian industries and defense organizations benefit from this research because a higher secret key rate could be useful in fighting against hackers and cyber fraud.