The Most Expensive Magic Trick in Quantum Computation

Synopsis

Quantum computers promise to tackle problems beyond the reach of even our most powerful classical machines, but turning that promise into a working device is another matter. The real challenge of quantum computing, we are often told, is keeping the fragile qubits from making mistakes. Surely, once we can correct the errors, we can get on with the computation? Unfortunately, the cure comes with a catch. The very protection that allows quantum information to survive also restricts what we can easily do with it. Protecting a quantum computer and persuading it to compute turn out to be two very different accomplishments.

In this talk, we will follow the surprising ideas that grew out of this tension and helped shape today’s vision of a fault-tolerant quantum computer. We will venture behind the familiar circuit diagrams to discover what the machine must actually do to bring them to life. There will be a little history, an inconvenient twist, and a solution that feels suspiciously like a magic trick. But even when the trick works, someone still has to pay the bill, and it is not cheap.