Research On Key Problems Of Universal Blind Quantum Computation Protocol

Although quantum computer research has achieved many fruitful results in recent years,quantum computing has extremely strict requirements on environment and physical equipment,which makes it a long-term vision to develop and produce small personal quantum computers at low prices.An ideal application model that is generally acknowledged is that large-scale quantum computers are used as service centers to provide remote quantum computing services to classical clients.In order to ensure the privacy of clients in the delegated quantum computing mode,the Universal Blind Quantum Computation(UBQC)protocol emerges as the times require.It has great theoretical significance and broad application prospects for the study of UBQC.The UBQC protocol is developed from the Measurement-Based Quantum Computation(MBQC)model,which consists of three parts: preparation,interaction measurement and channel transmission.However,factors such as noise environment and non-ideal equipment seriously restrict the performance of each stage of the UBQC protocol,namely,high efficiency,fault tolerance and security.Therefore,in order to provide clients with safe and efficient delegated quantum computing services,it is necessary to optimize all aspects of the UBQC protocol.The main research contents and innovations of this dissertation are as follows:(1)Aiming at the problem of low preparation efficiency in the UBQC protocol,the blind quantum state preparation protocol with the decoy state is studied.Based on the Remote Blind qubit State Preparation(RBSP)protocol,the RBSP protocol with two decoy states is proposed to reduce the number of optical pulses that need to be sent,thus improving the preparation efficiency.Theoretical analysis and experimental results show that the RBSP protocol with two decoy states can significantly reduce the number of optical pulses required to be sent.With the increase of transmission distance,the advantage of two decoy-state protocol become more apparent.(2)For the problem of degradation of preparation efficiency caused by finited data size in UBQC protocol,the finited data-size RBSP protocol with two decoy states is studied.Based on the finited data-size preparation protocol,the Statistical Fluctuation(SF)model is established to optimize the number of optical pulses required by the UBQC protocol in case of statistical fluctuations.Theoretical analysis and experimental resultsshow that when the transmission distance is short in the preparation protocol,the required number of pulses in case of statistical fluctuation is close to the asymptotic case without fluctuation.With the increase of the distance,the fluctuation performance is gradually obvious in the protocol.Based on SF model,the RBSP protocol with two decoy states can optimize the required number of pulses under fluctuation to improve the successful rate of prepareation,thus solving the degradation of the preparation efficiency under the finited data size.(3)Due to the qubit error caused by noises or devices,the fault-tolerant blind quantum computation protocol is studied.In order to correct the qubit error in the computation process of UBQC,the blind quantum error correction code preparation protocols are proposed based on the brickwork state and the cluster state respectively.The theoretical analysis shows that the quantum resource consumption is less in the clusterbased preparation protocol.In order to correct the qubit error in the preparation process,a fault-tolerant preparation protocol with cluster state is proposed,and the correctness and security proof of the protocol are given.Combining fault-tolerant preparation with the fault-toelrant computation of quantum error correction codes,a fault-tolerant UBQC protocol based on quantum error correcting codes is proposed.Theoretical analysis and experimental results show that the fault-tolerant UBQC protocol based on quantum error correction codes has better fault-tolerant performance at the teleportation layer of the encoded graph states,and the required number of optical pulses is less when the preparation success rate is the same.(4)Aiming at the impersonation and subsituation attacks of the classical channel in the UBQC protocol,the unconditionally secure authentication schemes of classical channel are studied.Based on the Wegman-Carter scheme,which is a combination of fixed strongly universal hash function and One-Time Pad(OTP),the security of the authentication scheme for the perfect and imperfect OTP key is analyzed respectively,and the attacker's impersonation probability and subsituation probability are given.Theoretical analysis and experimental results show that when the OTP key is perfect,the impersonation probability and the subsituation probability are independent of the number of authentication rounds.When the OTP key is imperfect,the impersonation probability increases slightly,but it still unchange with the number of authentication rounds;however,the subsituation probability increases exponential growth trend with the increasing number of authentication rounds.On this basis,the lifetime of the fixed strong universal hashfunction is given when the OTP key is imperfect,to ensure the unconditional security of the classical channel authentication of the UBQC protocol.