The history of quantum computing has been marked by a series of breakthroughs at the frontiers of materials and computer science. Applying the principles of quantum mechanics to build computers capable of delivering almost unimaginable leaps in performance over today’s machines has preoccupied scientists for more than 40 years. For all that, practical quantum computers have remained tantalisingly out of reach. News of a breakthrough this week suggests the finish line may finally be coming into sight, potentially opening the way to the first practical machines around the turn of the decade.
Google revealed that it had managed to overcome the inherent instability in a quantum system for the first time, successfully tackling the incoherence, or “noise”, that normally overwhelms the machines as they take on larger calculations. Like the first controlled nuclear chain reaction at the University of Chicago in 1942, it was the first concrete demonstration of something that had long been predicted in theory, and a threshold moment for the industry.
Yet even as the quantum computing era starts to loom into view, it is still difficult to anticipate exactly when its effects will be felt or how sweeping they will be. Google claimed five years ago to have achieved “quantum supremacy” — the point at which a quantum computer can solve a problem that would be impossible for a classical machine. But new programming techniques showed that today’s supercomputers could remain competitive for longer than expected. Even after the quantum era finally dawns, most computing will still take place on silicon-based machines, with only the most complex, specialised tasks moving to quantum systems.