Poster (Other)

FZJ-2016-04023

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Decoherence and Thermalization at Finite Temperatures for Quantum Systems

Novotny, M. (Corresponding author) ; Jin, F.FZJ* ; Yuan, S. ; Miyashita, S. ; De Raedt, H. ; Michielsen, K.FZJ*

2016

Please use a persistent id in citations: http://hdl.handle.net/2128/11963

Abstract: 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.

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Contributing Institute(s):

1. Jülich Supercomputing Center (JSC)

Research Program(s):

1. 511 - Computational Science and Mathematical Methods (POF3-511) (POF3-511)

Appears in the scientific report 2016

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Database coverage:

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