We investigate non-markovian dynamics of two interacting two-level systems by numerical solution of the stochastic Schroedinger equation (SSE). It is shown that non- markovian noises have significant influence on dynamics of atomic levels populations.
В работе исследуется динамика системы двух диполь-дипольно взаимодей- ствующих атомов в марковском и немарковском приближениях с помощью численного ре- шения стохастического уравнения Шредингера (СУШ). Показано существенное влияние немарковских шумов на динамику системы в виде осцилляций вероятностей обнаружить систему во втором и третьем энергетическом состоянии. Markovian and non-Markovian dynamics of two dipole-dipole interacting atoms is studied with the help of stochastic Schroedinger equation (SSE). It is shown that the non-Markovian effects are appeared in the form of oscillations of probabilities to find the systems in the entanglement states. Keywords: non-Markovian dynamics, stochastic Schrödinger equation, dipole-dipole interaction.
It is our aim to study the dynamics of a two-level atom immersed in the modified radiation field of a photonic band-gap material using non-Markovian stochastic Schr\"odinger equations. Up to now, such methodology has only been applied to toy models and not to physically realistic systems as the one presented here. In order to check its validity, we shall study several of the physical phenomena already described in the literature within non-Markovian master equations, such as the long-time-limit residual population in the excited level of the atom and the population inversion which occurs in the atomic system when applying an external laser field. In addition to the stochastic equation, we propose a non-Markovian master equation derived from the stochastic formalism, which in contrast to the current models of master equation preserves positivity. We propose a correlation function for the radiation field (environment) that captures many of the physically relevant aspects of the problem and describes the short-time behavior in a more accurate way than previously proposed ones. This characteristic permits a correct description of the fluctuations of the electromagnetic field, which in the stochastic formalism are represented by the noise, and a better description of the non-Markovian effects in the atomic dynamics. The methodology presented in this paper to apply stochastic Schr\"odinger equations can be followed to study more complex systems, like many-level atoms embedded in more complicated photonic band-gap structures.
Firstly, the Markovian stochastic Schrödinger equations are presented, together with their connections with the theory of measurements in continuous time. Moreover, the stochastic evolution equations are translated into a simulation algorithm, which is illustrated by two concrete examples — the damped harmonic oscillator and a two-level atom with homodyne photodetection. We then consider how to introduce memory effects in the stochastic Schrödinger equation via coloured noise. Specifically, the approach by using the Ornstein-Uhlenbeck process is illustrated and a simulation for the non-Markovian process proposed. Finally, an analytical approximation technique is tested with the help of the stochastic simulation in a model of a dissipative qubit.