Quantum bit error rate analysis of quantum key distribution via single-photon two-qubit states
Zihang Zhu · Journal of Optoelectronics·laser · 2013
The hybrid modulation quantum key distribution(QKD) via single-photon two-qubit states scheme is analyzed,and an improvement scheme is proposed.The input-output model of polarization is established.And the influence of the interferometers on the polarization coding is analyzed.Quantum bit error rate(QBER) of polarization coding caused by the phasic error of fast and slow axes and the alignment error between the basis vectors of polarization and polarization axis is simulated.Furthermore,the stability conditions of polarization are derived on this basis.The QBER of polarization coding can be influenced deeply by the fiber M-Z interferometers.The theoretic analysis reveals that the jitter of polarization state is not only derived from the birefringency,but also derived from coordinate system difference between incident light and fast and slow axes in fiber interferometer.Some necessary conditoins for the QKD via single-photon two-qubit states are given.The simulation show that when ρ and θ are both below 0.2 rad,the polarization QBER is less than 0.015.When ρ and θ are both below 0.4 rad,the polarization QBER is less than 0.06.The polarization QBER of 2%-5% in two-qubit QKD scheme could be accepted as far as the safety upper limit of QBER(11%) is concerned.