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Four Measurement Settings Are Both Necessary and Sufficient
For collective first and second moments of two qubits, structural bounds and explicit constructions certify a four-setting minimum.
Summary
For collective first and second moments of two qubits, structural bounds and explicit constructions certify a four-setting minimum.
The researchers ask how many orthogonal projective settings can estimate several observables without bias for arbitrary states. For two-qubit first and second moments, four settings are proven necessary and sufficient; an optimized design comes within about 0.0341 percent of a fixed-allocation variance lower bound. Finite-depth reconstruction adds bias, so the advantage depends on sample regime.
Why it matters
For collective first and second moments of two qubits, structural bounds and explicit constructions certify a four-setting minimum.
Limits and context
No additional limitation was separately recorded.
Key claims
For collective first and second moments of two qubits, structural bounds and explicit constructions certify a four-setting minimum.
Evidence: source-2026-10-28-019
Sources
- arXiv preprint 2610.36525, original v1arXiv · primary research
Corrections
No corrections have been recorded for this story.