  We analyze three quantum communication protocols that have been proposed in
the literature, and compare how well they communicate single-rail entanglement.
We use specific metrics for output state purity and probability of success and
include the presence of imperfect photon source and detection components. We
find that a distributed noiseless linear amplification (NLA) protocol with a
relay point placed half-way between Alice and Bob outperforms NLA at Bob's end
and a recently proposed purification protocol under most conditions, unless the
distance is very small or the photon source component is very good.
