  Quantum key distribution provides a promising solution for sharing secure
keys between two distant parties with unconditional security. Nevertheless,
quantum key distribution is still severely threatened by the imperfections of
devices. In particular, the classical pulse correlation threatens security when
sending decoy states. To address this problem and simplify experimental
requirements, we propose a phase-matching quantum key distribution protocol
without intensity modulation. Instead of using decoy states, we propose a novel
method to estimate the theoretical upper bound on the phase error rate
contributed by even-photon-number components. Simulation results show that the
transmission distance of our protocol could reach 305 km in telecommunication
fiber. Furthermore, we perform a proof-of-principle experiment to demonstrate
the feasibility of our protocol, and the key rate reaches 22.5 bps under a 45
dB channel loss. Addressing the security loophole of pulse intensity
correlation and replacing continuous random phase with 6 or 8 slices random
phase, our protocol provides a promising solution for constructing quantum
networks.
