Quantum secure direct communication(QSDC)enables the direct transmission of secret messages over a quantum channel without prior key sharing.QSDC implemented in the continuous-variable(CV)regime allows high-capacity i...Quantum secure direct communication(QSDC)enables the direct transmission of secret messages over a quantum channel without prior key sharing.QSDC implemented in the continuous-variable(CV)regime allows high-capacity information transmission using simple optical communication technologies.In this work,we propose a novel CV-QSDC protocol with a quantum one-time pad,which achieves secure message transmission based on coherent states and unitary operations,and the receiver can directly obtain the secret messages after measuring the coherent states.The security of this protocol is jointly guaranteed by one-time pad encryption and a CV quantum key distribution(QKD)protocol.Performance analysis shows that the proposed scheme can achieve a quantum bit error rate(QBER)lower than 1% by adjusting the modulation variance and unitary operation parameters.With the optimal modulation variance,the secure transmission distance of the proposed protocol can exceed 150 km.展开更多
We propose a novel fast numerical calculation method for the Rayleigh-Sommerfeld diffraction integral,which is developed based on the existing scaled convolution method.This approach enables fast cal-culations for gen...We propose a novel fast numerical calculation method for the Rayleigh-Sommerfeld diffraction integral,which is developed based on the existing scaled convolution method.This approach enables fast cal-culations for general cases of off-axis scenarios where the sampling intervals and numbers of the input and observation planes are unequal.Additionally,it allows for arbitrary adjustment of the sampling interval of the impulse response function,facilitating a manual trade-off between computational load and accuracy.The er-rors associated with this method,which is equivalent to interpolation,primarily arise from the discontinuities of the sampling matrix of the impulse response function on its boundaries of periodic extension.To address this issue,we propose the concept of the padding function and its construction method,and evaluate its ef-fectiveness in enhancing computational accuracy.The feasibility of the proposed method is verified by nu-merical simulation and compared with the direct integration DI-method in a simplified scenario.It shows that the proposed method has good computational accuracy for the general case where the sampling interval of the input and observation plane is not equal under non-near-field diffraction,and when the diffraction distance is large,although the computational accuracy of the proposed method cannot exceed that of the DI-method,the computational amount can be significantly reduced with almost no effect on the computational accuracy.This method provides a general numerical calculation scheme of diffraction in the non-near field case for areas such as computational holography.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.62402178 and 62501084)the Shandong Provincial Natural Science Foundation(Grant No.ZR2024QF285)the Qilu University of Technology(Shandong Academy of Sciences)Major Project(Grant No.2025ZDZX02)。
摘要Quantum secure direct communication(QSDC)enables the direct transmission of secret messages over a quantum channel without prior key sharing.QSDC implemented in the continuous-variable(CV)regime allows high-capacity information transmission using simple optical communication technologies.In this work,we propose a novel CV-QSDC protocol with a quantum one-time pad,which achieves secure message transmission based on coherent states and unitary operations,and the receiver can directly obtain the secret messages after measuring the coherent states.The security of this protocol is jointly guaranteed by one-time pad encryption and a CV quantum key distribution(QKD)protocol.Performance analysis shows that the proposed scheme can achieve a quantum bit error rate(QBER)lower than 1% by adjusting the modulation variance and unitary operation parameters.With the optimal modulation variance,the secure transmission distance of the proposed protocol can exceed 150 km.
摘要We propose a novel fast numerical calculation method for the Rayleigh-Sommerfeld diffraction integral,which is developed based on the existing scaled convolution method.This approach enables fast cal-culations for general cases of off-axis scenarios where the sampling intervals and numbers of the input and observation planes are unequal.Additionally,it allows for arbitrary adjustment of the sampling interval of the impulse response function,facilitating a manual trade-off between computational load and accuracy.The er-rors associated with this method,which is equivalent to interpolation,primarily arise from the discontinuities of the sampling matrix of the impulse response function on its boundaries of periodic extension.To address this issue,we propose the concept of the padding function and its construction method,and evaluate its ef-fectiveness in enhancing computational accuracy.The feasibility of the proposed method is verified by nu-merical simulation and compared with the direct integration DI-method in a simplified scenario.It shows that the proposed method has good computational accuracy for the general case where the sampling interval of the input and observation plane is not equal under non-near-field diffraction,and when the diffraction distance is large,although the computational accuracy of the proposed method cannot exceed that of the DI-method,the computational amount can be significantly reduced with almost no effect on the computational accuracy.This method provides a general numerical calculation scheme of diffraction in the non-near field case for areas such as computational holography.