15.6 Incompatible observables, 6.6, 6.7 Infinite square well, **3.2**; energy levels, 3.2; wave functions, 3.2; time evolution, 7.2 (ex) Inner product, **2.4**, **8.2**; properties, 8.2; Schwarz inequality, 8.2 (ex) Interference, quantum, 1.6, 7.3; single-photon, 1.6; two-slit, 1.6 Interpretation of