Roman Shakhovoy

Our study shows that the rate of random number generation by QRNG based on interference of laser pulses is significantly more limited than expected. An increase in generation speed requires shortening the duration of laser pulses. However, the interference of short laser pulses from a single laser diode is problematic due to jitter and phase modulation (chirp). The optically injection-locked configuration proposed by L. C. Comandar for MDI QKD does not have the above disadvantages and therefore enables the design of QRNG with a high speed of random number generation.

In this work, we demonstrate a new kind of attack on laser sources in quantum key distribution systems - the optical-pumping attack. We investigated its influence on a single distributed feedback laser diode and an optically injection-locked source configuration. The spectral dependency of this attack was also examined. We managed to increase the energy of emitted pulses using attackers light at several wavelengths. The developed optical-pumping attack should be considered as a possible threat to the security of QKD systems because the increase of pulse energy leads to overestimation of secret key rate between Alice and Bob, giving more information about secret key to Eve.

A remarkable aspect of quantum theory is that certain measurement outcomes are entirely unpredictable to all possible observers. Such quantum events can be harnessed to generate numbers whose randomness is asserted based upon the underlying physical processes. We formally introduce, design, and experimentally demonstrate an ultrafast optical quantum random number generator that uses a totally untrusted photonic source. While considering completely general quantum attacks and using dedicated FPGA hardware for post-processing, we certify and generate in real time random numbers at a rate of 8.05 Gb/s with a composable security parameter of 10^{−10}. Composable security is the most stringent and useful security paradigm because any given protocol remains secure even if arbitrarily combined with other instances of the same, or other, protocols, thereby allowing the generated randomness to be utilized for arbitrary applications in cryptography and beyond. This work achieves the fastest generation of composably secure quantum random numbers ever reported.