Prevent eavesdropping with bright reference pulses for practical quantum key distribution

We analyze the application of bright reference pulses to prevent the photon-number-splitting attack in weak-pulse quantum key distribution. It can extend the unconditional secure distance from 24.7 km to 169 km with up-present techniques. To overcome the after-pulses of avalanche-photodiode based single-photon detectors induced by bright reference pulses, additional improvement is put forward for practical applications