We report what we believe to be the first differential-phase quantum key distribution experiment using a series of quantum entangled photon pairs. We employed two outstanding techniques. As an entangled photon source, we used a band entangled photon pair source based on spontaneous four-wave mixing in a cooled dispersion-shifted fiber. As receivers, photon pairs were actively phase modulated with phase modulators followed by very stable planar light-wave circuit Mach–Zehnder interferometers, which provided two nonorthogonal measurements. As a consequence, we successfully generated sifted keys with a quantum bit error rate of 8.3% and a key generation rate of and revealed the feasibility of this QKD scheme.
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