Millimetre-scale chip when integrated into devices can be useful in future to make information security and to protect privacy
Researchers have shown that a chip-based device measuring a millimetre square could be used to generate quantum-based random numbers at gigabit per second speeds. The tiny device requires less power and could enable stand-alone random number generators or be incorporated into laptops and smartphones to offer real-time encryption.
The researchers report a quantum random number generator based on randomly emitted photons from a diode laser. Since the photon emission is inherently random, it is impossible to predict the numbers that will be generated.
Converts photons into optical power
The new chip was enabled by developments in silicon photonics technology, which uses the same semiconductor fabrication techniques used to make computer chips. It is now possible to fabricate waveguides into silicon that can guide light through the chip without losing the light energy along the way. These waveguides can be integrated onto a chip with electronics and integrated detectors that operate at very high speeds to convert the light signals into information.
The chip-based random number generator takes advantage of the situation that laser will emit photons randomly. The device converts these photons into optical power using a tiny device called an interferometer. Small photodetectors integrated into the same chip, detect the optical power and convert it into a voltage that can be turned into random numbers.
The new chip-based device is not only portable but also stable. As interferometers are sensitive to environmental conditions such as temperature, therefore, it is easier to control the temperature of a small chip.
Experimenting the chip
To experimentally test the design, the researchers had a foundry fabricate the random number generator chip. After characterising the optical and electronic performance, they used it for random number generation. They estimate a potential randomness generation rate of nearly 2.8 gigabits per second for their device, which would be fast enough to enable real-time encryption.
Although the chip containing the optical components is only one-millimetre square, the researchers used an external laser which provides the source of randomness, 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.