TY  - CONF
AU  - Novotny, Mark
AU  - Jin, Fengping
AU  - Yuan, Shengjun
AU  - Miyashita, Seiji
AU  - De Raedt, Hans
AU  - Michielsen, Kristel
TI  - Decoherence and Thermalization at Finite Temperatures for Quantum Systems
M1  - FZJ-2016-04023
PY  - 2016
AB  - We consider a quantum system $S$ with Hamiltonian ${\cal H}_S$ coupled via a Hamiltonian ${\cal H}_{SE}$ to a quantum environment $E$ with Hamiltonian ${\cal H}_E$.  We assume the entirety $S+E$ is in a canonical-thermal state at an inverse temperature $\beta$.   The entirety is a closed quantum system which evolves via the time-dependent Schr{\”o}dinger equation with Hamiltonian ${\cal H}={\cal H}_S+{\cal H}_E+\lambda{\cal H}_{SE}$ where $\lambda$ is the overall strength of the system-environment coupling.  Using both large-scale simulations and perturbation theory calculations in $\lambda$, we have studied a measure $\sigma(t)$ for decoherence and $\delta(t)$ for thermalization of $S$.  We performed large-scale parallel calculations on spin systems with up to $N=40$ spins in the entirety, with both real-time and imaginary-time quantum calculations.  We performed perturbation theory calculations about $\lambda=0$ and fluctuations about the average for the canonical-thermal ensemble, for both $\sigma$ and $\delta$.  We obtained closed form expressions for both $\sigma$ and $\delta$, in terms of the free energies of $S$ and $E$.  Our perturbation theory calculations agree very well with our numerical calculations, at least as long as $\beta\lambda$ is small.
T2  - 26th IUPAP International conference on Statistical Physics
CY  - 18 Jul 2016 - 22 Jul 2016, Lyon (France)
Y2  - 18 Jul 2016 - 22 Jul 2016
M2  - Lyon, France
LB  - PUB:(DE-HGF)24
UR  - https://juser.fz-juelich.de/record/811604
ER  -