Scientists have developed an on-chip component that entangles photons, bringing quantum technology to traditional silicon chips for the first time.

The component, known as a silicon-ring resonator, makes use of the unusual quantum phenomenon of entanglement, which allows two particles to form an instantaneous connection no matter how far away they are from each other.

Entanglement of light particles could be revolutionary for computing, transforming everything from communications to cybersecurity.

However, the new component is most significant for its scale.

Other photon-entangling technologies – known as micro-ring resonators – have previously been developed, but with a diameter of a few millimeters were far too large to fit onto a silicon chip.

The newly developed silicon-ring resonator is based on the same design but considerably smaller, allowing it to fit on a silicon chip.

“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,” explained Daniele Bajoni study co-author and researcher at the Università degli Studi di Pavia, Italy.

This difference in size is extremely important, as it makes it possible to bring quantum technology to traditional computers.

“In the last few years, silicon integrated devices have been developed to filter and route light, mainly for telecommunication applications,” said Bajoni.

“Our micro-ring resonators can be readily used alongside these devices, moving us toward the ability to fully harness entanglement on a chip.”

According to The Optical Society, which published the findings today in the journal Optica, the research could enable quantum technologies that have already been developed to be adopted on a wider scale.

“What has been missing was a cheap, small, and reliable source of entangled photons capable of propagation in fiber networks, a problem that is apparently solved by their innovation,” the society explained.

One example of this is the transmission of unbreakable quantum cryptography protocols, which are designed to provide truly secure data transmission but cannot work on existing infrastructure.

Looking further ahead, photon entanglement could even pave the way for instant data transmission, transforming whole areas of technology.

Silicon-ring resonators are based on the established micro-ring resonators, which take the form of a series of tiny loops etched onto wafers of silicon.

Each loop functions as a collector of photons, which it then re-emits.

The researchers have updated the design so that the silicon-ring resonators provide a new source of entangled photons while being small and efficient enough to be incorporated into a chip.

As part of this design, a laser beam is directed onto the silicon loops in the same direction as the photons being captured, allowing it to function as a power source for the loop-like resonator.

When the researchers analysed the photons being fired out, they found that a large number of them had become entangled.

“Our device is capable of emitting light with striking quantum mechanical properties never observed in an integrated source,” said Bajoni.

“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.”

Image courtesy of the Università degli Studi di Pavia.