Abstract
The question of an efficient multimode description of optical pulses is
studied. We show that a relatively very small number of nonmonochromatic
modes can be sufficient for a complete quantum description of pulses
with Gaussian quadrature statistics. For example, a three-mode
description was enough to reproduce the experimental data of photon
number correlations in optical solitons [S. Spalter, N. Korolkova, F.
Konig, A. Sizmann, and G. Leuchs, Phys. Rev. Lett. 81, 786 (1998)]. This
approach is very useful for a detailed understanding of squeezing
properties of soliton pulses with the main potential for quantum
communication with continuous variables. We show how homodyne detection
and/or measurements of photon number correlations can be used to
determine the quantum state of the multimode field. We also discuss a
possible way of physical separation of the nonmonochromatic modes.
