The search for a better, smaller, faster “true” random number generator—increasingly needed for strong cryptography and security—has fascinated technologists for many years, as they seek genuine probabilistic sources rather than those with even a tiny hint of determinism. This endeavor generally begins with an all-natural, physics-based phenomenon that defies any possibility of prediction.
In one of the most recent efforts, an international team of researchers, led by quantum-technology experts from the University of Bristol (U.K.), have developed a chip-based device that can be used to generate quantum-based random numbers at gigabit-per-second speeds.
They have demonstrated a silicon-on-insulator (SOI) quantum random number generator (QRNG) that uses phase fluctuations of the output a laser diode, where single photons are randomly emitted and thus generate an electrical signal that’s impossible to predict. All optical components (except the laser diode) and photodiodes are integrated onto a single monolithic device, fabricated by IMEC using industry-standard processing techniques. The laser diode is coupled to the circuit via an optical fiber.
The optical functions occupied less than 1 mm2 and were integrated onto a 2.5- × 2.5-mm SOI chip that was embedded and wirebonded to a 4- × 8-cm printed circuit board containing a transimpedance amplifier (TIA) and voltage supply for the photodiodes. Finally, the system was placed within a Faraday cage to reduce the RF noise pickup.