Quantum Random Number Generator Based On Twin Beams

Random numbers have significant applications in cryptography,statistical analysis,numerical simulation,etc.True randomness is an essential property of quantum physics.Quantum random number generator(QRNG)exploits the inherent randomness of a quantum event to produce true random numbers.Several optical QRNGs have been reported,such as QRNGs based on photon counting,attenuated pulse,phase noise of laser,quantum vacuum fluctuations,Raman scattering and optical parametric oscillators(OPO),etc.Recently,the QRNGs with bit rates up to Gbit/s have been achieved by some groups.QRNGs based on the photonic integrated circuit have been demonstrated experimentally,which shows the feasibility of integrated QRNGs.In the previous QRNG based on OPO,the phase of the macroscopic field is used to produce random numbers.In this thesis,we experimentally demonstrate a quantum random number generator based on twin beams.The twin beams generated in the parametric down-conversion are well-known to have intensity correlation and quantum entanglement.When a non-degenerate optical parametric oscillator(NOPO)is operated above threshold,the vacuum fluctuations are amplified and two orthogonally polarized twin beams are obtained.The intensity noises of the twin beams are measured directly by two photodetectors in the time domain respectively.And then the intensity noises of the twin beams are converted into the raw random numbers by a signal processing system.Two strings of quantum random numbers are extracted simultaneously with suitable post-processing algorithm.By post-selecting the identical data from two raw sequences and using suitable hash function,we also obtain two strings of identical quantum random numbers.The generated random numbers pass all NIST randomness tests.The presented scheme shows the feasibility of generating quantum random numbers from the intensity noises of macroscopic optical field.The main contents of this thesis are as follow:1.We utilize a NOPO operated above threshold to generate twin beams.We observed 75% quantum correlation between the intensity fluctuations of the twin beams in the time domain.With suitable post-processing algorithm,two strings of quantum random numbers with bit rates up to 60 Mbit/s are extracted simultaneously from the intensity noises of twin beams.2.By post-selecting the identical bits,we also obtain two strings of identical quantum random numbers with bit rates of 29.8 Mbit/s using the same device simultaneously.The extracted random numbers pass all NIST-STS randomness tests,which confirms the randomness of the generated random numbers.