EFFECTS OF DAMPING AND REAMPLIFICATION OF PURE NUMBER STATES

It is shown that in accordance with the results of Ning Lu [Phys. Rev. A 40, 1707 (1989)] the photon number state and the squeezed vacuum state are much more vulnerable to small loss than the coherent state. Furthermore, unlike the coherent state, they do not recover when the loss is compensated by a subsequent amplification. It is also shown that the Wigner function retains essential information about the original photon number of a decaying number state up to a loss of 1/2 of the original energy. © 1990 The American Physical Society.