Quantum Solitons: Control and Spectral Broadening

Quantum soliton (QS) evolution and highly nonclassical supercontinuum generation (SG) are noteworthy challenges in nonlinear quantum optics, which can be addressed by quantum control (QC) current techniques, as chopped random basis optimization (CRAB).

Optical QSs are the quantum counterpart of the self-localized propagation-invariant optical classical solitons (CSs). When the number of quanta goes to infinity, QSs tend to CSs. But, surprisingly, the evolution in the quantum regime is characterized by spreading. We control QSs by computing an optimal time-dependent perturbation to the Hamiltonian, achievable by dispersion or nonlinearity management in an optical fiber. By combining stochastic partial differential equations and CRAB, we look for the optimal control to limit quantum spreading and maximize SG. We find that QC allows to induce a steep-field gradient that enhances the QS spectral broadening.

The quantum deviation from the classical propagation of QSs is here ruled by the powerful QC tools to resemble CSs at low photon number regime or to obtain SG from quantum sources.