Fidelity

Fidelity

The scale runs from 0 to 1, and a score of 1 means the two states match up to a global phase. The mark sits near 1, which is the region where a long circuit can still accumulate a miss.

Fidelity is a score of how close two quantum states are, running from 0 to 1, and a score of 1 means they are the same state up to a global phase that no experiment sees. A gate fidelity is the same idea applied to an operation, scoring a real gate against the ideal one written on the page.

A score that looks very close to 1 can still disappoint in a long circuit, because small misses accumulate gate by gate. Malcolm does that accumulation on paper before he lets a percentage sound like reassurance.

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