Quantum Weak Values & Post-Selection

Pre-state θ_i: 45°
Post-state θ_f: 135°
Coupling g: 0.10
φ_i: 0°
φ_f: 0°

The weak value A_w = ⟨f|A|i⟩/⟨f|i⟩ of observable A (here σ_z) between pre-selected |i⟩ and post-selected |f⟩ states can exceed ±1 (anomalous), causing the measurement pointer to shift far beyond eigenvalue range. The pointer shift is Re(A_w)·g for weak coupling g.