A direct measurement independent quantum communication protocol secured from super eavesdroppers (Conference Presentation)

Abstract

Most quantum communication protocols like BB84 use non-orthogonal basis sets composed of orthogonal states, where an eavesdropper can access only 50% of the sender’s information. Thus, the overall eavesdropping rate becomes 25%, due to the same access rate of the receiver. This high error rate in a quantum channel provides an “Attack” sign to the system. However, the 25% attack to the quantum channel can no longer be effective if Eve can measure one conjugate variable without disturbing the other. Recently, such direct measurement techniques have been presented, and then most quantum communication protocols will be endangered eventually. Here we propose a direct measurement independent quantum communication (MIQC) protocol belongs to quantum secure direct communication (QSDC) systems. QSDC mostly relies on quantum entanglement and memories for direct message transfer, but it is more vulnerable due to direct information loss to Eve. Moreover, those QSDC protocols are not easy to implement and will become no longer of use if a direct measurement becomes possible. Our MIQC uses four conjugate variables composed of polarization and phase. To satisfy the measurement independence, we added two phase bases to the polarization-superposed single photons, where the phase selection is for random choices of spatially distinct quantum channels. Thus, Eve cannot know which path is chosen even if she can perfectly measure the encoded photon’s state. In our MIQC, Eve’s attack rate drops down to less than 1%, showing a measurement independent quantum communication protocol applicable to direct secure message transfers.