Photon-number fluctuation and correlation of bound soliton pairs in mode-locked fiber lasers

Quantum photon-number fluctuation and correlation of bound soliton pairs in mode-locked fiber lasers are studied based on the complex Ginzburg-Landau equation model. We find that, depending on their phase difference, the total photon-number noise of the bound soliton pair can be larger or smaller than that of a single soliton and the two solitons in the soliton pairs are with positive or negative photon-number correlation, correspondingly. It is predicted for the first time that out-of-phase soliton pairs can exhibit less noises due to negative correlation.