Measurement of laser-diode phase fluctuations generates random numbers

July 24, 2018
A small optical integrated circuit contains the needed interferometer, delay line, and so on. 
A chip-based device measuring a millimeter square can potentially generate quantum-based random numbers at gigabit-per-second speeds. The small square to the right of the penny contains all the optical components of the random-number generator. (Image Credit: Francesco Raffaelli, University of Bristol)

A quantum random-number generator based on phase fluctuations (random photon emission) from a laser diode and created as a monolithic optical integrated circuit has been developed by researchers at the University of Bristol (Bristol, UK); the active components occupy an area of less than one square millimeter on a silicon-on-insulator (SOI) chip 2.5 x 2.5 mm in size (which is mounted on a 4 x 8 cm printed-circuit board and placed in a Faraday cage to isolate it from surrounding RF noise).1

The device could be used to generate quantum-based random numbers at gigabit per second speeds; it requires little power and could enable stand-alone random number generators or be incorporated into laptops and smart phones to offer real-time encryption.

"While part of the control electronics is not integrated yet, the device we designed integrates all the required optical components on one chip," says Francesco Raffaelli, one fo the researchers.

Random-number generators are used to encrypt data transmitted during digital transactions such as buying products online or sending a secure e-mail. Today's random-number generators are based on computer algorithms, which can leave data vulnerable if hackers figure out the algorithm used.

To experimentally test their design, the researchers had a foundry fabricate the random-number generator chip. After characterizing the optical and electronic performance, they used it for random-number generation. They estimate a potential randomness generation rate of nearly 2.8 Gbit/s for their device, which would be fast enough to enable real-time encryption.

"We demonstrated random-number generation using about a tenth of the power used in other chip-based quantum random-number generator devices," says Raffaelli.

Although the chip containing the optical components is only one millimeter square, the researchers used an external laser to provide the source of randomness and electronics and measurement tools that required an optical table. They are now working to create a portable device about the size of a mobile phone that contains both the chip and the necessary electronics.



1. F. Raffaelli et al., Optics Express (2018); doi: 10.1364/OE.26.019730

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!