Random numbers are widely used nowadays, especially in computer science, information security and other fields. Furthermore, random numbers are of crucial importance in quantum key distribution, for they are the guarantee of security and essential in post-processing. The random number generators usually used now are of two kinds, one generates pseudo random numbers by computing, and the other one extracts randomness from classical physics processes, such as electric noises and thermal noises. However, theoretically, classical physics processes can be simulated, and only randomness from some quantum physics processes can generate true random numbers, for example collapse of quantum state. So, an important research direction of CREAM group is quantum random number generator (QRNG).

    Normally, generating of quantum random number contains four processes: selecting of randomness source, digital sampling of physical quantities, post-processing of number sequence and randomness testing. CREAM groups mainly aims at the problem of randomness source, and have proposed different schemes of QRNG with different sources. As for discrete-variable sources, we proposed the scheme based on detecting of single photons. And as for continuous-variable sources, we proposed several schemes, based on the measuring of phase noise or polarization noise of VCSEL source and the measuring of phase fluctuation of SLED source. We reached a high random number generating speed of 40Gbps (1.6Tbps with over sampling). Meanwhile, we did research on post-processing and randomness test, proposed the von Neumann bias correcting and 3-σ testing of quantum random numbers.


    CREAM group intends to propose more schemes as well as better test bacteria of QRNG, and produce quantum random number generators with higher speed, smaller size and more stable performance.

[1] Yu Liu, Mingyi Zhu, Bin Luo, Jianwei Zhang, and Hong Guo, “Implementation of 1.6 Tbs-1 truly random number generation based on a super-luminescent emitting diode,” Laser Phys. Lett. 10, 045001 (2013).
[2] Hong Guo, Wenzhuo Tang, Yu Liu, and Wei Wei, “Truly random number generation based on measurement of phase noise of a laser,” Phys. Rev. E 81 (5), 051137 (2010).