  Entanglement swapping is gaining widespread attention due to its application
in entanglement distribution among different parts of quantum appliances. We
investigate the entanglement swapping for pure and noisy systems, and argue
different entanglement quantifiers for quantum states. We explore the
relationship between the entanglement of initial states and the average
entanglement of final states in terms of concurrence and negativity. We find
that if initial quantum states are maximally entangled and we make measurements
in the Bell basis, then average concurrence and average negativity of final
states give similar results. In this case, we simply obtain the average
concurrence (average negativity) of the final states by taking the product of
concurrences (negativities) of the initial states. However, the measurement in
non-maximally entangled basis during entanglement swapping degrades the average
swapped entanglement. Further, the product of the entanglement of the initial
mixed states provides an upper bound to the average swapped entanglement of
final states obtained after entanglement swapping. The average concurrence of
finally obtained states provides an upper bound to the average negativity of
these states. We also discuss how successfully the output state can be used as
a channel for the teleportation of an unknown qubit.
