A bound on approximating non-Markovian dynamics by tensor networks in the time domain

• URL: http://arxiv.org/abs/2307.15592v2
• Date: Sun, 22 Oct 2023 17:47:11 GMT
• Title: A bound on approximating non-Markovian dynamics by tensor networks in the time domain
• Authors: Ilya Vilkoviskiy and Dmitry A. Abanin
• Abstract summary: We show that the spin-boson model can be efficiently simulated using in time computational resources. This bound indicates that the spin-boson model can be efficiently simulated using in time computational resources.
• Score: 0.9790236766474201
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: Spin-boson (SB) model plays a central role in studies of dissipative quantum dynamics, both due its conceptual importance and relevance to a number of physical systems. Here we provide rigorous bounds of the computational complexity of the SB model for the physically relevant case of a zero temperature Ohmic bath. We start with the description of the bosonic bath via its Feynman-Vernon influence functional (IF), which is a tensor on the space of spin's trajectories. By expanding the kernel of the IF functional via a sum of decaying exponentials, we obtain an analytical approximation of the continuous bath by a finite number of damped bosonic modes. We bound the error induced by restricting bosonic Hilbert spaces to a finite-dimensional subspace with small boson numbers, which yields an analytical form of a matrix-product state (MPS) representation of the IF. We show that the MPS bond dimension $D$ scales polynomially in the error on physical observables $\epsilon$, as well as in the evolution time $T$, $D\propto T^4/\epsilon^2$. This bound indicates that the spin-boson model can be efficiently simulated using polynomial in time computational resources.

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