Editing Openai/6897769e-4ee4-800f-aba5-69cca34f701c (section)

===== Quantum decoherence can be modelled by coupling the system (atom + photon mode) to an environment. A Lindblad master equation is a standard phenomenological form: =====

ρ˙=−iℏ[H,ρ]+∑k(LkρLk†−12{Lk†Lk,ρ}),\dot\rho = -\tfrac{i}{\hbar}[H,\rho] + \sum_k \Big( L_k \rho L_k^\dagger - \tfrac12\{L_k^\dagger L_k,\rho\}\Big),ρ˙=−ℏi[H,ρ]+k∑(LkρLk†−21{Lk†Lk,ρ}),
where the jump operators LkL_kLk represent environmentally induced transitions (absorption, emission). When the system couples strongly to many degrees of freedom (the detector), off‑diagonal coherences in the measured basis decay rapidly — that is the physical mechanism underlying “wavefunction collapse” in operational terms. The rate scales like (coupling strength)2^22 × (environment spectral density), so stronger photon exchange → faster decoherence → “the future becomes classical” in the QAT sense.