Anastasiya Ponosova

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.

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.

We report recent advances in the development of certification for quantum key distribution (QKD) systems. We give an example of a commercial QKD system that we have analysed for possible loopholes, improved to close the vulnerabilities identified, and designed a set of tests for that can be used by a certification lab [arXiv:2310.20107]. We explain some of the testbenches in this lab, such as an ultrawide spectral characterisation testbench, automated detector testing, and laser damage testbench that verifies the quality of a power limiter. This work is in line with the requirements of the ISO standard for QKD and paves the way for the creation of certification services.

We propose an original device that can protect quantum key distribution (QKD) systems from the effects of intense laser radiation. Carbon nanomaterials dispersed in a polymer can be used as a fuse that interrupts key distribution when Eve tries to hack the system by high-power laser emission. Moreover, it saves system components from laser damage.