Most random number generators (RNGs) are based on computer algorithms known as pseudo-random number generators, which are fast but not truly random. A short string of bits from a pseudo-RNG appears random, but eventually the sequences repeat. Moreover, if you know the inner workings of the algorithm, you can predict the exact sequence. This is troubling in communications security, where random numbers are used to choose encryption keys. In contrast, quantum random number generators (QRNGs) extract randomness from quantum mechanical processes that are believed to be truly random and unpredictable.
Random number generators are essential to ensuring performance in information technologies, including cryptography, stochastic simulations, and massive data processing. The quality of random numbers ultimately determines the security and privacy that can be achieved, while the speed at which they can be generated poses limits to the utilization of the available resources. In this work we propose and demonstrate a quantum entropy source for random number generation on an indium phosphide photonic integrated circuit made possible by a new design using two-laser interference and heterodyne detection. The resulting device offers high-speed operation with unprecedented security guarantees and reduced form factor. It is also compatible with complementary metal-oxide semiconductor technology, opening the path to its integration in computation and communication electronic cards, which is particularly relevant for the intensive migration of information processing and storage tasks from local premises to cloud data centers.