Lindblad Master Equation — Open Quantum Decay

The Lindblad equation dρ/dt = −i[H,ρ] + Σ_k γ_k(L_k ρ L_k† − ½{L_k†L_k,ρ}) governs open quantum systems. For a qubit, it describes decoherence (loss of phase) and relaxation (energy decay) as the Bloch vector spirals toward the equilibrium point.