Coherent preparation of the biexciton state in a semiconductor quantum dot coupled to a metallic nanoparticle

We study the potential for controlled transfer of population to the biexciton state of a semiconductor quantum dot coupled with a metal nanoparticle, under the influence of an electromagnetic pulse with hyperbolic secant shape, and derive analytical solutions of the density matrix equations, for both zero and nonzero biexciton energy shift. These solutions lead to efficient transfer to the biexciton state, for various interparticle distances, including relatively small values. In certain cases, when the distance between the two particles is small, the transfer of population is strongly modified because of the influence of surface plasmons to the excitons, and the effect is more pronounced for shorter pulses. The hybrid snanostructure that we study has been proposed for generating efficiently polarization-entangled photons, thus the successful biexciton state preparation considered here is expected to contribute in this line of research.