The need for spatial and spectral filtering in the generation of polarization entanglement is eliminated by combining two coherently-driven type-II spontaneous parametric downconverters. The resulting ultrabright source emits photon pairs that are polarization entangled over the entire spatial cone and spectrum of emission. We detect a flux of ∼12 000 polarization-entangled pairs/s per mW of pump power at 90% quantum-interference visibility, and the source can be temperature tuned for 5 nm around frequency degeneracy. The output state is actively controlled by precisely adjusting the relative phase of the two coherent pumps.
@article{arxiv.quant-ph/0309071,
title = {Generation of ultrabright tunable polarization entanglement without spatial, spectral, or temporal constraints},
author = {Marco Fiorentino and Gaetan Messin and Christopher E. Kuklewicz and Franco N. C. Wong and Jeffrey H. Shapiro},
journal= {arXiv preprint arXiv:quant-ph/0309071},
year = {2009}
}