Millimetre-scale silicon chip generates quantum-random-numbers for information security

A team of international researchers, led by quantum technology experts from the University of Bristol, have shown that a chip-based device can be used to generate quantum-based random numbers at gigabit per second speeds.

The tiny device, with a footprint of just a millimetre square, requires little power to operate and could enable stand-alone random number generators and be incorporated into laptops and smartphones to offer real-time encryption.

PhD student Francesco Raffaelli from the University of Bristol’s Quantum Engineering Technology Labs (QET Labs) , has led the work, which is presented today in The Optical Society of America’s journal Optics Express .

He said: “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.”

“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.”

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

Francesco added: “Not only is our device little, but it is very fast. 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.”

This new chip was enabled by developments in using silicon photonics for quantum technology, which continues to be a major activity in Bristol. The motivation is to make quantum technologies, including quantum random number generation, using the same semiconductor fabrication techniques used to make computer processors.

Although the chip reported today contains all the optical components needed for the scheme within one-millimetre square, the researchers used external electronics and measurement tools for testing and analysis that required space in a research lab. The team are now working to create portable devices, about the size of a mobile phone, that contains both the chip and the necessary electronics.