Spectral correlation control in down-converted photon pairs

Abstract

Sources of photon pairs based on the spontaneous parametric down-conversion process are commonly used for long-distance quantum communication and quantum information processing. The key feature for improving the range of transmission is engineering their spectral properties. Our analysis shows the way for full control of spectral correlation within a fiber-coupled photon pair. The result of extensive numerical simulations allows us to specify the settings for the generation of pairs featuring positive-energy correlation, which can potentially improve the signal-to-noise ratio in practical implementation of quantum communication protocols. We analytically and numerically analyze the characteristics of a source based on a $\ensuremath{\beta}$-barium borate crystal cut for type-II phase matching at the degenerated frequencies $755\phantom{\rule{4pt}{0ex}}\mathrm{nm} \ensuremath{\rightarrow}1550\phantom{\rule{4pt}{0ex}}\mathrm{nm}+1550\phantom{\rule{4pt}{0ex}}\mathrm{nm}$. The presented framework is general and can be applied to other crystals.