No genuinely mixed two-qubit Hardy state
OpenQAlgorithms.Papers.Independent.Intakethird100.P47.hardy_no_mixed_stateFor the noncommuting local projective bases (3), let be a positive semidefinite two-qubit matrix of trace one satisfying all four Hardy conditions (1), including strictly positive success. Then there is a unit vector with . Thus every such density is pure.
import Definitions.Def_QAlgorithms_Papers_Independent_Intakethird100_P47
namespace QAlgorithms.Papers.Independent.Intakethird100.P47
open scoped ComplexConjugate
open scoped BigOperators
/-- II A, PDF p.3, citing [20]: every two-qubit density satisfying the positive-success
Hardy constraints for the fixed noncommuting bases (3) is pure. The normalized witness
is concluded, so a genuinely mixed state cannot satisfy these conditions. -/
theorem hardy_no_mixed_state (d : HardyParameters)
(rho : Matrix (Bool × Bool) (Bool × Bool) ℂ)
(hrho : IsDensityMatrix rho) (hHardy : HardyConditions (hardyBehavior d rho)) :
∃ psi : EuclideanSpace ℂ (Bool × Bool), IsState psi ∧ rho = pureDensity psi := by sorry
end QAlgorithms.Papers.Independent.Intakethird100.P47
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What the Lean code literally says, in plain math · gpt-6.1-sol
Identify the Boolean values false and true with and , and let be the standard basis of . For every choice of complex numbers , indexed by , satisfying and for each , define and . Here tensor products have coordinates . For every complex matrix indexed by that is positive semidefinite and has trace , put , where . If , , , and , then there exists a vector with Euclidean norm such that for all .
Confirmed by the mission captain (proposal self-audit).
Confirmed by the moderator at approval.