 Foundations II: Measurement and Evolution by John Preskill

Caltech quantum-computation lecture notes, chapter 3.

Verified primary passages: sections 3.4.2–3.4.3, printed pp. 33–37, equations (3.125)–(3.132), unitary system-environment phase damping and spontaneous-emission amplitude damping. Diagonal populations are constant in the phase-damping example, but change in the amplitude-damping example while off-diagonal coherence is suppressed. Reuses the existing John Preskill and Work by John Preskill headers.