1. 轨道：|x_j⟩ = |𝒜⟩|E_j⟩；|p_j⟩ = SELECT|x_j⟩
2. 关键内积：⟨x_j|p_j⟩ = ⟨𝒜|SELECT|𝒜⟩ 作用在 |E_j⟩ 分支 = E_j/λ =: Ẽ_j（加权和还原 A）
3. 勾股：‖|p_j⟩ − Ẽ_j|x_j⟩‖² = 1 − Ẽ_j² → 定义 |q_j⟩ = (|p_j⟩ − Ẽ_j|x_j⟩)/√(1−Ẽ_j²)
4. W|x_j⟩ = SELECT|x_j⟩ = |p_j⟩ = Ẽ_j|x_j⟩ + √(1−Ẽ_j²)|q_j⟩（反射固定辅助为 |𝒜⟩ 的分量）
5. W|p_j⟩ = SELECT·(2Ẽ_j|x_j⟩ − |p_j⟩) = 2Ẽ_j|p_j⟩ − SELECT²|x_j⟩ = 2Ẽ_j|p_j⟩ − |x_j⟩（用 SELECT² = I）
6. 换基排矩阵：W|K_j = [Ẽ_j, −√(1−Ẽ_j²); √(1−Ẽ_j²), Ẽ_j] = R_y(2θ_j)，θ_j = arccos Ẽ_j
7. 特征方程 μ² − 2Ẽ_j·μ + 1 = 0（判别式 4(Ẽ_j²−1) ≤ 0）→ μ = Ẽ_j ± i·√(1−Ẽ_j²) = e^{±iθ_j}