Ideal quantum clocks and the measurement of time
  The recently introduced concept of an "ideal quantum clock" (IQC) is extended. Especially it is shown that the time operator of an IQC is canonically conjugated to the Hamiltonian of the IQC in a certain pre-Hilbert space. Further it is discussed how the IQC interacts with another physical system D and to what extent the IQC measures the time differences of any prescribed initial and final states of D. 
Walter Gessner
quant-ph