Micro ring could hasten the adoption of quantum cryptography

Engineers from Università degli Studi di Pavia have created a micro-ring that entangles individual particles of light. The design is based on a micro ring resonator, a loop etched onto a silicon wafer that can capture and emit particles of light. By tailoring the resonator's design, the researchers created a small and highly efficient source of entangled photons.

"The main advantage of our new source is that it is small, bright and silicon based," said researcher Daniele Bajoni. "The diameter of the ring resonator is 20µm. Previous sources were hundreds of times larger than the one we have developed.

"In the last few years, silicon integrated devices have been developed to filter and route light, mainly for telecommunication applications," he continued. "Our micro-ring resonator can be readily used alongside these devices, moving us toward the ability to fully harness entanglement on a chip."

The research could find application in quantum information technologies –and quantum cryptography protocols in particular. According to Bajoni and his colleagues, these protocols have been demonstrated and tested, but what has been missing was a cheap, small, and reliable source of entangled photons capable of propagation in fibre networks.