QAOA(三):能保证什么

1. H_C = (3/2)I − ½(Z₀Z₁ + Z₁Z₂ + Z₂Z₀),C_max = 2(奇圈切不断三边)

2. 对称性约化到 span{|a⟩,|b⟩}:|s⟩ = ½|a⟩ + (√3/2)|b⟩(系数由内积 ⟨a|s⟩ = ½、⟨b|s⟩ = √3/2 算出);ΣX 矩阵 [[0,√3],[√3,2]],λ²−2λ−3 = 0 → λ = 3、−1,|s⟩ 是 λ = 3 的本征矢

3. 子流形 β = γ/2 + π/2 上 F = 30/16 + (3/4)c − (9/8)c²,c = cos 2γ;dF/dc = 3/4 − (9/4)c = 0 → c = 1/3

4. F_max = 30/16 + 4/16 − 2/16 = 32/16 = 2 = C_max → r₁ = 1;γ = ½·arccos(1/3) ≈ 0.6155、β ≈ 1.8786;六个最优串各占 1/6

5. 样本核对(N = 12、六串各 2 次):⟨Z₀Z₁⟩ = (2−8+2)/12 = −1/3 → F̂ = 3·(1−(−1/3))/2 = 2 ✓

类型integration(定理卡)+ worked-example(K₃ 闭式演算)