Relation between information and disturbance in quantum key distribution   protocol with classical Alice
  The "semiquantum" key distribution protocol introduced by Zou et al. [Phys. Rev. A Vol.79, 052312 (2009)] is examined. The protocol while using two-way quantum communication requires only Bob to be fully quantum. We derive a trade-off inequality between information gained by Eve and the disturbance observed by legitimate users. It guarantees that Eve cannot obtain large information if the disturbance is sufficiently small. 
Takayuki Miyadera
quant-ph