Quantum Reference Frames and Relativistic Time Operator
  Aharonov-Kaufherr model of quantum space-time which accounts Reference Frames (RF) quantum effects is considered in Relativistic Quantum Mechanics framework. For RF connected with some macroscopic object its free quantum motion - wave packet smearing results in additional uncertainty of test particle coordinate. Due to the same effects the use of Galilean or Lorentz transformations for this RFs becomes incorrect and the special quantum space-time transformations are introduced.   In particular for any RF the proper time becomes the operator in other RF. This time operator calculated solving relativistic Heisenberg equations for some quantum clocks models.   Generalized Klein- Gordon equation proposed which depends on both the particle and RF masses. 
S.Mayburov