In order to assess inelastic effects on two fermion entanglement production, we address
an exactly solvable
two-particle scattering problem where the target is an excitable scatterer. Useful
entanglement, as measured by
the two particle concurrence, is obtained from post-selection of oppositely scattered
particle states. The S
matrix formalism is generalized in order to address nonunitary evolution in the
propagating channels. We find
the striking result that inelasticity can actually increase concurrence as compared to
the elastic case by increasing
the uncertainty of the single particle subspace. Concurrence zeros are controlled by
either single particle
resonance energies or total reflection conditions that ascertain precisely one of the
electron states. Concurrence
minima also occur and are controlled by entangled resonance situations where the electron
becomes entangled
with the scatterer, and thus does not give up full information of its state. In this
model, exciting the scatterer
can never fully destroy phase coherence due to an intrinsic limit to the probability of
inelastic events. |