The lure of quantum entangled computing is strong, as it can provide a means of impenetrable encryption — but the hardware has always been too bulky to make it practical. Now, though, researchers have shrunk the technology down to less than the width of a human hair, small enough to squeeze onto a chip.
The new device, developed by researchers from the Università degli Studi di Pavia in Italy, is based on a silicon technology known as a micro-ring resonator. A small loop etched onto silicon, the structures can gather and reemit particles of light. But by making some clever tweaks to the device, they have been able to make the device entangle photons — making them a practical means for quantum entanglement at the computer chip scale. Daniele Bajoni, one of the researchers, explains:
"The main advantage of our new source is that it is at the same time small, bright, and silicon based. The diameter of the ring resonator is a mere 20 microns, which is about one-tenth of the width of a human hair. Previous sources were hundreds of times larger than the one we developed. Our device is capable of emitting light with striking quantum mechanical properties never observed in an integrated source. The rate at which the entangled photons are generated is unprecedented for a silicon integrated source, and comparable with that available from bulk crystals that must be pumped by very strong lasers."
Although the old component size of a few millimetres sounds small, it's impractically large to use on a silicon wafer. The new device still requires the generation of laser light, pumped into the device using an optical fibre — but it's still mercifully small.
The applications are obvious. The development could the first time facilitate the creation of computer chips that allow the use of quantum cryptography protocols on everyday devices. The practicalities of quantum encryption have already been demonstrated; we were just waiting for small-scale devices to make it work for everyday folks. It may still be a way off yet, but at least we know it's a definite possibility. [Optics Info Base via EurekAlert via Engadget]