Fidelity balance in quantum operations

Phys Rev Lett. 2001 Feb 12;86(7):1366-9. doi: 10.1103/PhysRevLett.86.1366.

Abstract

I derive a tight bound between the quality of estimating the state of a single copy of a d-level system, and the degree the initial state has to be altered in the course of this procedure. This result provides a complete analytical description of the quantum mechanical trade-off between the information gain and the quantum state disturbance expressed in terms of mean fidelities. I also discuss consequences of this bound for quantum teleportation using nonmaximally entangled states.