Quantum technology researchers from the University of Bristol have developed a silicon chip that can generate quantum-based random numbers at gigabit speeds.

The silicon chip is just one square millimetre (shown bottom right above next to a penny) and needs little power to operate and could enable stand-alone random number generators in laptops and smartphones to offer real-time encryption.

“Randomness is needed to secure our communication and storage of information using data encryption. Physicists have known for some time that the nature of quantum mechanics can make randomness that is not easy to copy and impossible to predict,” said Francesco Raffaelli from the University of Bristol’s Quantum Engineering Technology Labs who led the work.

“We designed and tested a chip made of silicon and works using light to do just this. It integrates all the required optical components on one chip that can be made with industry-standard fabrication — this brings the power of quantum randomness much closer to being integrated into our personal computers and our smartphones,” he said.

The researchers use a technique where single photons are randomly emitted from a diode laser in such a way that when they enter the chip, a random electrical signal is output that is impossible to predict. This provides the random number generator that is at the heart of many data encryption techniques.

“Not only is our device little, but it is very fast,” said Raffaelli. “The generation rates we achieve are competitive with the generation rates demonstrated in experiments using big and bulky optics that, unlike silicon photonics, cannot be integrated with mass-manufacturable technology.”

The chip was enabled by developments in using silicon photonics for quantum technology, which continues to be a major activity in Bristol.

The team are now working to create portable devices, about the size of a mobile phone, that contains both the chip and the supporting electronics that would eventually be integrated into a single chip for the consumer market.