In a keynote speech given in late 2017, the physicist John Preskill coined the term Noisy Intermediate Scale Quantum (NISQ) technology for the kinds of quantum computers that will be available in the next few years. Here, ‘noisy’ refers to the fact that the devices will be disturbed by what is happening in their environment. For instance, small changes in temperature, or stray electric or magnetic fields, can cause the quantum information in the computer to be degraded — a process known as decoherence. To overcome this, we need to be able to perform error correction — essentially looking at the system to determine which disturbances have occurred, then reversing them.