Optimal strategies for estimating the average fidelity of quantum gates

Understand

We show that the minimum experimental effort to characterize the proper functioning of a quantum device scales as 2^n for n qubits and requires classical computational resources ~ n^2 2^{3n}.

• This represents an exponential reduction compared to the best currently available protocol, Monte Carlo characterization.
• The reduction comes at the price of either having to prepare entangled input states or obtaining bounds rather than the average fidelity itself.
• It is achieved by applying Monte Carlo sampling to so-called two-designs or two classical fidelities.