QuantumQuokka
Phase Stripping Fidelity Estimation ✨🎯📊
Sample- and Hardware-Efficient Fidelity Estimation by Stripping Phase-Dominated Magic
Published: 12 May 2026 · Updated: 13 July 2026
Read the original sourceWhat the paper says
They came up with 'phase stripping' that lets you estimate fidelity with only O(poly(n)) samples instead of EXPONENTIAL!!
The Critique
The 'phase stripping' requires knowing the target state's phase structure... but if you already know the target state, why are you measuring it?! This is the ultimate chicken-and-egg problem! And they never quantify how 'close to phase states' your state needs to be—at what point does the sample complexity blow up again?!
Why It Matters
If the method requires prior knowledge of the state being estimated, it's not useful for experimental characterization where the goal is to learn unknown states.
What They Missed
They assume perfect fan-out gates, ignoring gate errors that would propagate through the nonlinear post-processing.
The Big Question
How do you perform phase stripping when the target state is a priori unknown, and how robust is this to realistic gate errors?