Research On Fiber Quantum Cryptography And Quantum Fingerprinting

Quantum information is a subject to study information science based on quantum physics.It has many advantages compared with the classic information science.Based on the basic principles of quantum mechanics one can achieve quantum key distribution(QKD).It can do key expansion with theoretically unconditionally security.Combined with one-time-pad encryption,we can finally achieve unconditionally secure commu-nication.Based on quantum state superposition and its interference,the quantum fin-gerprint can save more transmitted information than classical algorithms.And quantum random number which is based on the quantum measurement hypothesis,is more secure than classical random number.It is theoretically unpredictable.In this paper,we first introduce a new QKD scheme with high anti-channel tur-bulence.Normal QKD scheme put a restrict threshold on system error rate.But this scheme can tolerate much higher error rate,up to 50%theoretically.After that we in-troduce some of the shortcomings of the original protocol,then we proposed a passive implementation of this protocol,and demonstrated its ability to resist high channel tur-bulence.At the distance of 53 km,the bit error rate is as high as 31.2%and our new protocol still can generated secure keys.This surpasses other QKD protocols,and is expected to apply to the environment where the turbulence is large.Fingerprinting is an important part of classic information theory.In order to let Referee to determine whether Alice and Bob has the same information,Alice and Bob only need to send a short "fingerprint" data to Referee.If we want to compare two n bits strings using classical method,it is needed to send the amount of information on the order of the(?).However,because of quantum state superposition,n qubits can have 2n orthogonal basis.So that n qubits can carry much more information than n classical bits.That is,theoretically only log2 n order of the qubits can complete the task of fingerprint comparison.In this paper,we first introduced a more practical coherent state scheme for quantum fingerprinting,demonstrating that it also had the exponential advantage of the transmitted information.Then we do a long-range quantum fingerprinting experiment.By optimizing the performance of each part,at a total distance of 20 km we achieve the fingerprinting which the transmitted information is superior to the classical theoretical limit.It is the farthest quantum fingerprinting experiment,and it is the first quantum fingerprinting experiment beyond the limit of classical information theory.Random number generator is also a key component in the field of communication.Classic random numbers are usually generated by pseudo-random number generators or classical physical random number generators.The security of the former depends on the computational complexity,and the latter can not be fully proved immune to the at-tacker.The generation of quantum random numbers depends on the quantum mechanics hypothesis,and its randomness is not affected by the attacker under the framework of quantum mechanics.In this paper,we propose a scheme to generate random numbers without the trust of the measurement device.While maintaining the theoretical security of the quantum random number,we also turn off the possible loopholes caused by the use of the real detectors,and further improve its practical security.