Abstract
We report on a systematic experimental study of heralding efficiency and generation rate of
telecom-band infrared photon pairs generated by spontaneous parametric down-conversion and coupled to single mode optical fibers. We define the correlated-mode coupling efficiency--an inherent
source efficiency--and explain its relation to heralding efficiency. For our experiment, we developed
a reconfigurable computer controlled pump-beam and collection-mode optical apparatus which we
used to measure the generation rate and correlated-mode coupling efficiency. The use of low-noise,
high-efficiency superconducting-nanowire single-photon-detectors in this setup allowed us to explore
focus configurations with low overall photon flux. The measured data agree well with theory and we
demonstrated a correlated-mode coupling efficiency of 97 +-2%, which is the highest efficiency yet
achieved for this type of system. These results confirm theoretical treatments and demonstrate that
very high overall heralding efficiencies can, in principle, be achieved in quantum optical systems. It
is expected that these results and techniques will be widely incorporated into future systems that
require, or benefit from, a high heralding efficiency.
