A high speed quantum random number generator with quantum phase noise

Feihu Xu (University of Toronto), Bing Qi (University of Toronto), Xiongfeng Ma (University of Toronto), He Xu (University of Toronto), Haoxuan Zheng (Department of Physics, MIT) and Hoi-Kwong Lo (University of Toronto)

 

Quantum random number generator (QRNG) can generate truly random numbers with information-theoretically provable randomness from the probabilistic nature of fundamental quantum processes. Unfortunately, the practical applications of most QRNGs are limited by the system complexities and relatively low generation rate. Here, we experimentally demonstrate a simple and high speed QRNG based on measuring the quantum phase noise of a laser operating at a low intensity level. Our previous study [B. Qi et al, Opt. Lett. 35, 312, 2010] has shown that the quantum phase noise of laser can be harnessed to generate truly random numbers. In this letter, we substantially improve this technology and report success in generating random numbers at a rate up to 6.25 Gbits/s. This rate is already an order of magnitude faster than any previously reported QRNG and comparable to the widely used pseudo RNGs. The hardware implementation of the system is simple and robust for practical applications. One important issue that hasn't been fully addressed before, is that in principle the randomness originated from various classical sources can be known and even controlled by an adversary or Eavesdropper (Eve) so that the generated random numbers may not be completely random to Eve. Our approach to deal with this problem is to quantify the quantum randomness (randomness from quantum sources) and classical randomness separately. We determine the experimental parameters by maximizing the quantum randomness and theoretically analyze the quantum randomness by bounding the min-entropy. By employing sophisticated randomness extractor, the ¯nal random numbers originate only from the irreducible quantum randomness.