Weilong Wang

Quantum random number generator (QRNG) relies on the intrinsic randomness of quantum mechanics to produce true random numbers which are important in many fields. QRNGs with semiconductor light source have attracted a lot of attention due to their operational simplicity and high generation rate. However, the temperature of light source may vary due to imperfect devices and other factors. There is still a lack of study on the effects of temperature variations on the security of practical QRNG. We fill this gap by presenting a numerical method for studying the effects of temperature increase on the super-luminescent emitting diode (SLED) based QRNG and propose some strategies toward robust QRNG against temperature increase.

The finite-key security of the standard three-intensity decoy-state quantum key distribution QKD) protocol in the presence of information leakage has been analyzed (Wang et al. in New J Phys 20:083027, 2018). On the other hand, the 1-decoy state QKD protocol has been proved to be able to achieve higher secret key rate than the three-intensity decoy-state QKD protocol in the finite-key regime by using only two different intensity settings (Davide et al. in Appl Phys Lett 112:171104, 2018). In this work, we analyze the finite-key security of the 1-decoy state QKD protocol with a leaky intensity modulator, which is used to generate the decoy state. In particular, we simulate the secret key rate under three practical cases of Trojan-horse attacks. Our simulation results demonstrate that the 1-decoy state QKD protocol can be secure over long distances within a reasonable time frame given that the intensity modulator is sufficiently isolated. By comparing the simulation results to those presented in Wang et al. (2018), we find that, as expected, the 1-decoy state QKD protocol is more robust against information leakage from the intensity modulator for all achievable distances.

We propose a quantum key distribution scheme that combines a biased basis choice with the decoy-state method. In this scheme, Alice sends all signal states in the Z basis and decoy states in the X and Z basis with certain probabilities, and Bob measures received pulses with optimal basis choice. This scheme simplifies the system and reduces the random number consumption. From the simulation result taking into account of statistical fluctuations, we find that in a typical experimental setup, the proposed scheme can increase the key rate by at least 45% comparing to the standard decoy-state scheme. In the postprocessing, we also apply a rigorous method to upper bound the phase error rate of the single-photon components of signal states.