Experimental quantum key distribution with active phase randomization

Abstract

Phase randomization is an important assumption made in many security proofs of practical quantum key distribution (QKD) systems. Here, the authors present the first experimental demonstration of QKD with reliable active phase randomization. One key contribution is a polarization-insensitive phase modulator, which they added to a commercial phase-coding QKD system to randomize the global phase of each bit. They also proposed a useful method to verify the phase randomization experimentally. Their result shows very low quantum bit error rate (<1%). They expect this active phase randomization process to be a standard part in future QKD setups due to its significance and feasibility. © 2007 American Institute of Physics.