@misc{9237009,
  abstract     = {{This thesis investigates the quantum dynamics of a three-level laser system described by the Scovil and Schulz--DuBois model with emphasis on the emergence of classical laser behaviour. In particular we study the time evolution from an initially coherent quantum field. We compare closed Jaynes--Cummings dynamics with open Lindblad dissipator dynamics including hot and cold Markovian reservoirs, which provide lasing gain in the cavity field. This provides a unified setting for studying coherence, dissipation, and phase-space dynamics. We determine if the decoherence of the system can be predetermined by Jaynes--Cummings model and a Schawlow-Townes like estimate for a strong and weak coupling regime, respectively. 

Numerically, we show that the model follows the expected quantum optical behaviour. The numerical implementation was improved substantially through vectorisation and by benchmarking two integrators. The fourth-order Runge--Kutta method was found to be significantly more efficient than the forward Euler method, yielding an improvement in computational speed by a factor of $\sim 80$ for the parameter ranges considered.

From the simulation we find that the Jaynes--Cummings model holds for the strong--coupling regime and that indicators like the Husimi Q--function must be interpreted together with density-matrix-based observables to confirm quantum coherence. In the open system the coherence decays over time and the cavity field evolves toward a phase-averaged, annular shaped distribution in phase space, consistent with the expected steady-state behaviour of a laser. In the weak--coupling regime, the fitted coherence lifetime agrees well with a Schawlow-Townes-like phase diffusion estimate. This suggests that the Schawlow--Townes description becomes appropriate once coherent Jaynes--Cummings dynamics no longer dominate the cavity evolution.}},
  author       = {{Christov, Oskar}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{Coherence and Classical Emergence in the Scovil and Schulz-DuBois Laser Model}},
  year         = {{2026}},
}