Decoy state method could effectively enhance the performance of quantum keydistribution (QKD) with practical phase randomized weak coherent source.Although active modulation of the source intensity is effective and has beenimplemented in many experiments, passive preparation of decoy states is also animportant addition to the family of decoy state QKD protocols. In this paper,following the theory of Curty \emph{et al.} [PRA, 81, 022310 (2010)], weexperimentally demonstrate the phase-encoding passive-decoy-state QKD with onlylinear optical setups and threshold single photon detectors. In our experiment,two homemade independent pulsed lasers, with visibility of Hong-Ou-Mandelinterference $0.53(\pm 0.003)$, have been implemented and used to passivelygenerate the different decoy states. Finally, secret key rate $1.5\times10^{-5}$/pulse is obtained with 10km commercial fiber between Alice and Bob.
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