  Measurement-device-independent quantum key distribution (MDI-QKD) protocol
was proposed to remove all the detector side channel attacks, while its
security relies on the trusted encoding systems. Here we propose a one-sided
MDI-QKD (1SMDI-QKD) protocol, which enjoys detection loophole-free advantage,
and at the same time weakens the state preparation assumption in MDI-QKD. The
1SMDI-QKD can be regarded as a modified MDI-QKD, in which Bob's encoding system
is trusted, while Alice's is uncharacterized. For the practical implementation,
we also provide a scheme by utilizing coherent light source with an analytical
two decoy state estimation method. Simulation with realistic experimental
parameters shows that the protocol has a promising performance, and thus can be
applied to practical QKD applications.
