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Back in 2001, an obscure group of theoretical physicists proved a remarkable result. They showed that it was possible to build a quantum computer out of ordinary optical components, such as mirrors, lenses, lasers and so on.

That was something of a surprise. Until then, physicists had thought that quantum computing would only be possible using non-linear crystals and other exotic components that are hard to control.

The prospect of using ordinary bits and pieces has an important consequence. It immediately suggests that more powerful devices can be built simply by adding extra components. This problem of scalability has always plagued other attempts to build quantum computers.

The reaction from the theoretical physics community was barely controlled excitement. But in practice, this approach has never lived up to its early promise. That’s because it is hard to build even ordinary optical components into chip-like devices that can be scaled like conventional silicon chips. It is just not possible to manufacture them with the required performance and tolerances.

Today, Benjamin Metcalf at the University of Oxford and a few pals show how they are tackling these problems while aiming for the ultimate goal of scalable quantum computation. These guys have built the first self-contained photonic chip capable of teleportation, one of the fundamental logic operations necessary for quantum computation. The device is a proof-of-principle demonstration that scalable quantum computers of this type are firmly in the crosshairs of experimental physicists. But it also reveals that significant challenges lay ahead.

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