Photon pairs on a computer chip could enable secure quantum communications


A TEAM of researchers co-led by RMIT scientists have pioneered a new approach to create photon pairs that fit on a computer chip.

The breakthrough could enable the next generation of integrated quantum optical technology, which would be compatible with current technology and secure communications.

The new approach is based on a micro-ring resonator, a tiny optical cavity in which energy conservation constraints can be exploited to amplify quantum processes, even w hile suppressing classical effects.

The researchers used laser beams at different wavelengths and then had to overcome the risk of the two pump beams being able to destroy the photons’ fragile quantum state.

RMIT MicroNano Research Facility Director Professor David Moss says one of the properties of light exploited within quantum optics is ‘photon polarisation’, which is the direction in which the electric field associated with the photon oscillates.

“Processes used to generate single photons or photon pairs on a chip allow the generation of photons with the same polarisation as the laser beam, forcing us to find a way to directly mix, or cross-polarise, the photons via a nonlinear optical process on a chip for the first time,” Prof Moss explained.

Moss worked with Professor Roberto Morandotti at the INRS-EMT in Canada and researchers from the University of Sussex and Herriot Watt University, City University of Hong Kong, and the Xi’an Institute in Chin, on the research.

“While a similar suppression of classical effects has been observed in gas vapours and complex micro-structured fibres, this is the first time it has been reported on a chip, opening a route for building scalable integrated devices that exploit the mixing of polarization on a single photon level,’’ he said.

The fabrication process for the chip is compatible with current technology, allowing the use of CMOS fabrication infrastructure to create these chips.