Suppression of Exciton Fine-Structure Splitting in Anisotropic Colloidal Quantum Dots for Applications in Quantum Communications

On-demand sources of indistinguishable and entangled photon pairs are needed for implementations of quantum repeaters. These devices can be based on a single semiconductor quantum dot (QD) employed for the generation of polarization-entangled photon pairs via a biexciton-exciton emission cascade. The key factor enabling its realization is the ability to find QDs with almost zero fine-structure splitting (FSS) of the exciton radiative doublet. Here we analyze conditions where FSS suppression can occur in colloidal nanocrystals and demonstrate its feasibility. This would open the possibility to use low-cost colloidal QDs in quantum communications.