I noticed for some quantum information processing protocols such as teleportation, entanglement distillation, bound entanglement activation, entanglement catalysis, the protocols seem to have a similar structure as:
(1) A certain task can not be achieved with a certain system configuration.
(2) Then an extra entangled system is attached to the original system.
(3) A local unitary operation is carried out (not always since in entanglement catalysis we do not do this)
(4) A local measurement is carried out.
(5) Communication of the measurement result.
(6) A local post-operation is applied depending on the measurement results.
(7) The task is accomplished (may need multiple iterations of the above operations)
For me, it seems that the key components are:
(1) Attaching an extra entangled system
(2) Local measurement
(3) Communication of measurement results and post-operations
What's the physical(mathematical) meaning of these operations? Why they all have such a structure? Is there anything in common among these protocols?