  The ultimate limits of continuous-variable single-mode quantum teleportation
due to absorption are studied, with special emphasis on (quasi-)monochromatic
optical fields propagating through fibers. It is shown that even if an
infinitely squeezed two-mode squeezed vacuum were used, the amount of
information that would be transferred quantum mechanically over a finite
distance is limited and effectively approaches to zero on a length scale that
is much shorter than the (classical) absorption length. Only for short
distances the state-dependent teleportation fidelity can be close to unity. To
realize the largest possibly fidelity, an asymmetrical equipment must be used,
where the source of the two-mode squeezed vacuum is nearer to Alice than to Bob
and in consequence the coherent displacement performed by Bob cannot be chosen
independently of the transmission lengths.
