On Nondemolition Measurements of Photon Number: A Comment on quant-ph/0612031

  • Vladimir S. MASHKEVICH
  • Published 2007

Abstract

Experimental results stated in [1] are seminal: The authors have realized nondemolition measurements of the photon number. As to the interpretation of the results, it seems to be less than convincing: The treatment of the system state and of the role of measurement is not compatible with the conventional point of view. We propose an adequate treatment, in which the experimental results are a manifestation of a partial Zeno effect (a slowdown of relaxation). E-mail: Vladimir.Mashkevich100@qc.cuny.edu 1 Experimental results stated in [1] are seminal: The authors have realized nondemolition measurements of the photon number. As to the interpretation of the results, it seems to be less than convincing: The treatment of the system state and of the role of measurement is not compatible with the conventional point of view. We quote some statements: “A QND detection . . . realizes an ideal projective measurement which leaves the system in an eigenstate of the measured observable. It can therefore be repeated many times, leading to the same result until the system jumps into another eigenstate under the effect of an external perturbation.” “Our experiment realizes for the first time. . . situation in which the jumps of a field oscillator are revealed via QND measurements . . . ” “The atoms in the QND experiment are witnessing a quantum relaxation process whose dynamics is intrinsically not affected by the measurement.” These statements along with the full text imply that the field oscillator is at any time in a pure state with a state vector |t〉 := |oscillator t〉 = 0,∞ ∑

Cite this paper

@inproceedings{MASHKEVICH2007OnNM, title={On Nondemolition Measurements of Photon Number: A Comment on quant-ph/0612031}, author={Vladimir S. MASHKEVICH}, year={2007} }