Dipole-dipole interaction in a photonic crystal nanocavity.

We put forward a general classical approach to obtain the quantum dipole-dipole interaction (DDI) between two two-level "atoms" in arbitrary nanostructures, in which the transfer rate of the DDI is analytically expressed as the difference between the two classical dipoles' total radiation power and the sum of the two individual dipole's radiation powers. The radiation power can be calculated by the finite-difference time-domain method. We apply the theory to investigate the DDI in a photonic crystal nanocavity. It is found that strong DDI at a distance can be achieved under resonant conditions and with a high quality factor, and the attractive or repulsive properties of the DDI can be manipulated. Our results should be significant for solid-state quantum-information processing based on the DDI [ABSTRACT FROM AUTHOR]