Quantum correlations in the soliton collisions

We study quantum correlations and quantum noise in the soliton collision described by a general two-soliton solution of the nonlinear Schr\"odinger equation, by using the back-propagation method. Our results include the standard case of a $sech$-shaped initial pulse analyzed earlier. We reveal that double-hump initial pulses can get more squeezed, and the squeezing ratio enhancement is due to the long collision period in which the pulses are more stationary. These results offer promising possibilities of using higher-order solitons to generate strongly squeezed states for the quantum information process and quantum computation.