For the three-terminal NSN device with single-mode normal terminals and
without Coulomb blockade, we propose an approach which allows us to
consistently characterize the device operation as that of a Cooper pair
splitter in terms of scattering matrix elements as well as in terms of
measurable quantities. The obtained explicit expression for the splitting
probability notably contains the two-particle interference term not available
from conductance measurements. We show that splitting doesn't necessarily rely
on crossed Andreev reflection thus allowing for the unit efficiency at zero
energy. Our results imply that the current cross-correlator generally doesn't
provide definite measure of splitting.Comment: 6 pages + 10 pages Supplemental Materia