A research team from the University of Science and Technology of China has made security analysis and improvement of Source Independent Quantum Random Number Generators (SI-QRNGs) with imperfect devices.
By studying the actual characteristics of the measurement devices of the source-independent QRNGs, the researchers pointed out that the security issues were caused by after-pulse, detection efficiency mismatching, poor sensitivity to photon number distribution in measurement devices, etc., and gave the corresponding solutions.
The SI-QRNG protocol is a new quantum random number protocol proposed in 2016. This protocol can generate secure random numbers under the condition that the light source is completely untrusted by monitoring the error code of the mutual unbiased basis corresponding to the base of the random number generation. It can simultaneously meet the requirements of security and high rate of random number generator, and has a very high devices loss tolerance. However, this protocol has some security problems.
In this study, the researchers evaluated the impact of these problems on actual security.
To solve the problem of detection efficiency mismatch and poor detector sensitivity to the distribution of light source, the researchers proposed a method for monitoring the distribution of light source, and gave a bit rate formula based on the composable security with full consideration to the finite length effect. (Phys.org)
The work has been published in npj Quantum Information.