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Hardy Paradox Advances Quantum Parameter Estimation with Post-Selection Efficiency Insights

A team of quantum physicists has leveraged Hardy’s paradox to create a post‑selected phase‑estimation protocol that dramatically improves measurement sensitivity. By engineering a contextuality‑violating state, they achieved a quantum Fisher information gain up to four times the standard limit. The peak enhancement occurs when the overlap parameter |⟨0|a⟩|² is around 0.55, while efficiency declines sharply beyond 0.5. The work demonstrates that quantum paradoxes can serve as practical resources for advanced metrology.