A strong correlation is found in the linear polarization of pairs of photons emitted by individual quantum dots, even though their time-averaged emission is unpolarized. This is consistent with an asymmetric dot shape, as is the exciton level splitting of 26 μeV determined from photoluminescence spectra. We find that the photon pairs are emitted with an equal probability into just two polarization modes. This intrinsic property of the source can be combined with polarization sensitive optics to passively encode random data for quantum key distribution.

• Received 25 April 2002

DOI:https://doi.org/10.1103/PhysRevB.66.081302