Quantum computers, networked together using shared entanglement, permit us to carry out a wide variety of new communication protocols. But how well can these networks be implemented, using today’s technology? In this video, David will introduce the quantum repeater, a crucial ingredient in the realization of quantum networks over long distance. He will then outline some of the differences between ground-based and space-based quantum networks, the two types which are the subject of current research.

Main takeaways

• The quantum repeater is a small quantum device which can convert multiple entangled states distributed over short distances into a single entangled state distributed over a large distance.
• This is essential, because otherwise, the probability of Bob receiving a quantum state sent by Alice would decay exponentially as a function of the distance between them.
• In the absence of quantum repeaters, a classical device can be used in repeating signals, as long as the device is trusted.
• We can use entanglement distillation to combat the effects of noise in quantum channels, by consuming multiple noisy entangled states in order to produce a single less noisy state.