Chaotic Timing for High-Speed Photonic Random Bit Generation

Description

High-speed generation of random bits is required in the areas of computation and secure communications. Compared to pseudo-random bits based on deterministic algorithms, random bit generation (RBG) based on physical devices are usually preferred because of the better randomness quality. In particular, photonic devices with wide bandwidths are useful sources of physical entropy for high-speed RBG. Photonic RBG has been investigated through various approaches based on quantum fluctuations, optical noise, and semiconductor lasers. With the capability of synchronization of fast dynamics, chaotic semiconductor lasers have attracted much attention for RBG through the endeavors of various groups, including our group, over the past years. However, the bandwidths of the intrinsic chaotic signals require fast postprocessing electronics. This is exemplified by the common use of analog-to-digital converters with a fine resolution of over 16 bits and a large bandwidth of over 10 GHz for RBG. Such a dependence on the postprocessing electronics not only increases the cost but also implies possible contamination of thermal noise during detection.In this proposal, RBG will be investigated by extracting timing randomness in chaotic dynamics of semiconductor lasers through both experiments and simulations. The approach relies on a semiconductor laser subject to perturbations of different forms into chaos and a fiber appended for subsequent nonlinear propagation, which will result in some rare occurrences of strong pulsations. Firstly, the irregular time intervals between the rarely occurring high-intensity pulses will be converted into random bits through triggered sampling of fast digital electrical clocks. Secondly, the chaotic signals will be analyzed for its complexity to ensure the randomness quality of the output, as linked to the evaluation of the correlation dimensions of the chaotic waveforms generated under different perturbations. Thirdly, correlated RBG will be investigated through linking two arms of bit generation using progressively secure ways for key distribution, where the consistency of nonlinear propagation in fibers and synchronization of chaotic lasers are utilized. Overall, the proposed approach based on the chaotic timing offers some unique advantages. It does not sensitively rely on the amplitude of the emission intensity. It avoids the possible contamination of electronic thermal noise. It does not require fast electronics for analog-to-digital conversion. By successfully utilizing the timing information of the rare pulses, the simplification of hardware and improvement in correlation will be achieved for high-speed RBG.