Superluminal Signals in Quantum Optics

Theoretically and experimentally the superluminal signals arising at passage of an electromagnetic
pulse through thermally excited media are investigated. It is shown that the equations of quantum
electrodynamics solved by standard methods explain the appearance of such signals as a
consequence of fluctuation properties of secondary quantum fields. It is indicated that quantum
averages from operators of electric strength and magnetic strength in these signals are equal to zero.
The field energy is different from zero. Such signals have no classical analogues. The effective
superluminal velocity of the laser beam after it crosses the cylindrical parallel layer of thermally
excited atoms has been calculated. The results of experiments to measure the effective superluminal
velocity of the beam passing a cylindrical layer of air inside a hot metal tube are given. Quantitative
agreement of theoretical and experiment data is stated.