Optical quantum random number generator based on orbital angular momentum of light

Random numbers are critical to both classical and quantum cryptography. A key necessity for random-number generators is that their outputs must be unpredictable. The computer generated random numbers are pseudo-random and using them in cryptography causes unexpected security-holes. True randomness can only be extracted from the inherently random process such as quantum phenomena. Among different types of quantum random number generator, those are based on quantum optics attract more attention because of their advantages such as easier implementation, higher random number generation rate, and compact size. The quantum optical random number generators can be classified into three main classes according to the type of randomness sources and quantum measurement. In this paper, a new idea to generate truly random numbers based on the superposition of photon’s orbital angular momentum (OAM) degrees of freedom is proposed. Our proposed technique which belongs to the first class of optical QRNGs can enhance both the generation rate and unpredictability of random bit string.