Generating dark solitons by single photons

We show that dark solitons in 1D bose systems may be excited by resonant absorption of single quanta of an external ac field. The energy of the quantum $\hbar\omega$ should be slightly blue-detuned from the energy of a soliton with momentum $\hbar q$, where $q$ is the external field wavenumber $q$. We calculate the absorption cross-section and show that it has power-law dependence on the frequency detuning. This reflects the quantum nature of the absorption process and the orthogonality catastrophe phenomenon associated with it.