Unitary limit in crossed Andreev transport
  One of the most promising approaches of generating spin- and energy-entangled electron pairs is splitting a Cooper pair into the metal through spatially separated terminals. Utilizing hybrid systems with the energy-dependent barriers at the superconductor-normal metal interfaces, one can achieve practically 100% efficiency outcome of entangled electrons. We investigate minimalistic one-dimensional model comprising a superconductor and two metallic leads and derive an expression for an electron-to-hole transmission probability as a measure of splitting efficiency. We find the conditions for achieving 100% efficiency and present analytical results for the differential conductance and differential noise. 
I. A. Sadovskyy, G. B. Lesovik, V. M. Vinokur
cond-mat.mes-hall cond-mat.supr-con quant-ph