  We develop a theory to teleport an unknown quantum state using entanglement
between two distant parties. Our theory takes into account experimental
limitations due to contribution of multi-photon pair production of parametric
down conversion source, inefficiency and dark counts of detectors and channel
losses. We use a linear optics setup for quantum teleportation of an unknown
quantum state by performing Bell state measurement by the sender. Our theory
successfully provides a model for experimentalists to optimize the fidelity by
adjusting the experimental parameters. We apply our model to a recent
experiment on quantum teleportation and the results obtained by our model are
in good agreement with the experiment results.
