STAGE OFFRE DE STAGE: PROBABILITY BOUNDS OF NON-UNITARY QUANTUM OPERATIONS

In quantum mechanics there are several fundamental tasks that we cannot perform, otherwise we would violate the linearity of the theory. For example cloning, perfect amplification, distinguishing non-orthogonal states, etc…

Nevertheless, one can still achieve these tasks as long as one doesn’t violate linearity on average. This is typically possible by resorting to entanglement and postselection, but postselection introduces a finite probability of success, which is lower the more the task is demanding.

The objective of this stage is to craft a unified model for non-unitary operations and to use it to find a general bound on the probability of success of any non-unitary operation. Finally, we could show that other known bounds for specific tasks are only particular cases of this general bound.