Real-time selection for free-space measurement device independent quantum key distribution

Abstract

In consideration of the time-dependent transmittance caused by atmospheric turbulence, we combine real-time selection (RTS) method with measurement device independent quantum key distribution (MDI-QKD). The modified scheme filters out the intervals with high channel transmittance and thus in turn increases the secure key rate. The optimal threshold of post-selection is determined by an iterative algorithm in advance, which balances the decrease in the total number of signals and the increase in average transmittance. Simulation results show that our modified scheme has apparent advances in both maximum tolerant loss and secure key rate compared to the original MDI-QKD protocol. The MDI-QKD with RTS even performs better when the level of turbulence becomes larger. Furthermore, the modified scheme is more stable against the statistical fluctuation as well.