Optical Quantum Communication Protocols

量子通信比我们今天的经典通信提供了前所未有的能力。海森堡的不确定性原理允许在两个相距遥远的方之间创建密钥，而不需要对连线上的窃听者进行计算假设，原因很简单，因为对手试图查看信号都会干扰信号。在量子信息中，经典比特正在被量子位所取代，量子位不仅可以取0或1的值，还可以取两者之间的连续状态。这有助于，例如，比较大的文件或日程安排约会，因为人们可以将更多不同的信息编码成更少的量子信号。

Quantum communication offers unprecedented abilities over what we can today with classical communication. Heisenberg's Uncertainty Principle allows creating secret keys between two distant parties without computational assumption about eavesdroppers along the connecting line, simply because any attempt by an adversary to look at the signal will disturb it. In quantum information, classical bits are being replaced by qubits, which cannot only take values zero or one, but a continuum of states in-between. That helps, for example, in comparing large files or schedule appointments as one can encode many more different messages into a smaller number of quantum signals. The generation of secret key using quantum key distribution is a maturing field with first commercial applications. However, we need to make it work faster to keep up with the increasing communication rates of modern optical communication. For this, we need to find better ways to deal with signal loss in optical fibers as we cannot use traditional signal amplification, as is done in classical optical communication. Such amplification will disturb the signal exactly like an eavesdropper would do. Quantum mechanics offers in principle alternative methods, called quantum repeaters. They have not been demonstrated yet as the known schemes involve very fragile systems and operations. Our research will develop more robust and practical methods. The quantitative advantage of quantum communication over classical communication is known since two decades, but until recently, it was not known how to practically implement the protocols to realize that advantage. Recently, we proposed and demonstrated optical protocols to realize the advantage in comparing data files. We will now work to expand the achievable tasks to include quantum-efficient scheduling of appointments in a group of users. This progress is not only important in saving communication costs in networks, but the protocols we propose also leak less information about the compared files or calendar entries to the communication parties. This fits well into the paradigm of Privacy by Design put forward the Ontario Privacy Commissioner. In our research, not only do we expand the range of tasks that we can realize in our modern optical communication networks, we also train people who are familiar with these extended capabilities and can carry their knowledge into Canada's communication industry.