Quantum Communication: How quantum signals help to maintain privacy and speeds things up

In Communication Protocols such as comparison of data and scheduling appointments, there are typically two important questions: how much bandwidth do I need to complete the task, and how much information about my local data do I leak out to my partners during the protocol? After all, when comparing data it is only important to find out whether they agree or not, but not what the data are. Same for scheduling: we want to find a joint open time-slot, but don’t want to reveal all our busy times. Quantum communication allows us to improve over classical communication in both aspects: it can use less signal to accomplish the task, and it can leak just enough information about the local data to the partners to accomplish the task, but not more.

Quantum communication protocols are usually formulated in rather abstract way, thought of more as a theoretical curiosity than a practical idea. We will see that there are ways to achieve some of the goals with rather simple tools from optical communication, just run in the quantum regime. I will review our theoretical and experimental progress for the comparison of data (quantum finger-printing) and give an outlook to the scheduling problem.