  A recent paper, Quantum backaction of optical observations on Bose-Einstein
condensates by U. Leonhardt, T. Kiss, and P. Piwnicki, Eur. Phys. J. D7, 413
(1999), emphasized that the limit of dispersive imaging of Bose-Einstein
condensates with off-resonant light is not residual absorption, but a different
form of quantum backaction of the probe light. This note points out that these
conclusions are incorrect, and that Rayleigh scattering is the dominant quantum
backaction of dispersive imaging.
