Engineering tour de force births programmable optical quantum computer

Enlarge / The maze: as a photon you must run it. But your path will be changed by your partner photon. (credit: Nature)

There comes a moment in every physicist's life when they think the unthinkable: I wish I were an engineer. I suspect this thought crossed the minds of the 14-odd physicists involved in creating a key demonstration of the scalability of quantum computing using light.

At the moment, if you had to bet on the technology most likely to win the quantum computing race, most people would put their chips on a spread of superconducting rings. But I'd put the house and kids on light. Why? Because lasers make everything better. More seriously, quantum computing architectures based on superconducting devices have made remarkable progress in the last five to ten years. By contrast, progress on the light front has been ominously slow. But it should be easier to work with light-based qubits if we can ever get them off the ground.

Why I love photons

Photons, as far as I'm concerned, still make the best quantum bits (qubits). This is because photons mostly pass through the world unhindered. A photon, in a super-special quantum state, can go from air to an optical fiber to air, through a silicon chip, back into air, and into a fiber again, all without destroying its quantum state. About all you need to ensure is that your photon detector is in the dark so that only the qubit photons hit it.

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