Bounds on quantum process fidelity from quantum state fidelity measurements and optimal discrimination of projective single-qubit measurements

Bounds on quantum process fidelity from quantum state fidelity measurements and optimal discrimination of projective single-qubit measurements

Seminar author:Jaromir Fiurasek

Event date and time:03/27/2014 04:30:pm

Event location:IFAE seminar room

Event contact:

In the first part of my talk I will present our recent work on estimation of fidelity of quantum gates. To certify that an experimentally implemented quantum transformation is a certain unitary operation U on a d-dimensional Hilbert space, it suffices to determine fidelities of output states for d+1 suitably chosen pure input states. The set of these d+1 probe states can consist of d orthogonal states that form a basis and one additional state which is a balanced superposition of all d basis states.
In this talk, I will provide an analytical lower bound on quantum process fidelity for two-qubit quantum gates which results from the knowledge of average state fidelity for the basis states and the fidelity of the superposition state. This bound will be compared with the Hofmann bound that is based on knowledge of average state fidelities for two mutually unbiased bases and possible extension of these findings to N-qubit operations will be discussed.