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Excitonic models of light-harvesting complexes, where the vibrational degrees of freedom are treated as a bath, are commonly used to describe the motion of the electronic excitation through a molecule. Recent experiments point toward the…

Quantum Physics · Physics 2011-07-19 Christoph Kreisbeck , Tobias Kramer , Mirta Rodriguez , Birgit Hein

Tree tensor network states (TTNSs) combined with the density matrix renormalization group (DMRG) are emerging as powerful tools for vibrational and vibronic structure simulations in molecules with strong coupling and fluxionality. In this…

Chemical Physics · Physics 2026-05-28 Henrik R. Larsson , Brieuc Le Dé , Gino E. Gamboni

The hierarchical equations of motion (HEOM) approach can describe the reduced dynamics of a system simultaneously coupled to multiple bosonic and fermionic environments. The complexity of exactly describing the system-environment…

Time- and frequency resolved optical signals provide insights into the properties of light harvesting molecular complexes, including excitation energies, dipole strengths and orientations, as well as in the exciton energy flow through the…

Chemical Physics · Physics 2018-06-15 Tobias Kramer , Matthias Noack , Alexander Reinefeld , Mirta Rodriguez , Yaroslav Zelinskyy

We unite two of the most widely used approaches for strongly damped, non-Markovian open quantum dynamics, the Hierarchical Equations of Motion (HEOM) and the pseudomode method by proving two statements: First, every physical bath…

Quantum Physics · Physics 2026-04-09 Kai Müller , Walter T. Strunz

We investigate the disordered spin-$\frac12$Heisenberg model in two dimensions and employ tree tensor networks (TTNs) with a physics-informed structural optimization of the tree layout, to simulate dynamics in the many-body localization…

Disordered Systems and Neural Networks · Physics 2025-12-23 Lars Humpert , Dante M. Kennes , Jan-Niklas Herre

Hybrid Tensor Networks (hTN) offer a promising solution for encoding variational quantum states beyond the capabilities of efficient classical methods or noisy quantum computers alone. However, their practical usefulness and many…

To investigate a system coupled to a harmonic oscillator bath, we propose a new approach based on a phonon number representation of the bath. Compared to the method of the hierarchical equations of motion, the new approach is…

Quantum Physics · Physics 2020-01-08 M. Tokieda , K. Hagino

We present a tensor network model (TNM) for forecasting nonlinear and chaotic dynamics, bridging quantum many-body methods with classical complex systems. The TNM leverages hierarchical tensor contractions to encode non-Markovian temporal…

Quantum Physics · Physics 2025-11-13 Jia-Bin You , Jian Feng Kong , Jun Ye

We study truncations of hierarchical equations of motion (HEOM) for finite-dimensional open quantum systems. We prove that for finite-dimensional approximations constructed with a Schur-complement type of terminator, the spectrum converges…

Quantum Physics · Physics 2026-04-27 Vasilii Vadimov

Approaching the long-time dynamics of non-Markovian open quantum systems presents a challenging task if the bath is strongly coupled. Recent proposals address this problem through a representation of the so-called process tensor in terms of…

Quantum Physics · Physics 2024-05-20 Valentin Link , Hong-Hao Tu , Walter T. Strunz

In non-perturbative non-Markovian open quantum systems, reaching either low temperatures with the hierarchical equations of motion (HEOM) or high temperatures with the Thermalized Time Evolving Density Operator with Orthogonal Polynomials…

Quantum Physics · Physics 2025-03-05 Brieuc Le Dé , Amine Jaouadi , Etienne Mangaud , Alex W. Chin , Michèle Desouter-Lecomte

Out-of-equilibrium dynamics of non-integrable Hamiltonian many-body quantum systems are characterized by highly entangled wave functions. Near-maximal entanglement arises in systems exhibiting thermalization or pre-thermalization, where the…

This paper proposes a novel higher-order multi-scale (HOMS) computational method, which is highly targeted for efficient, high-accuracy and low-computational-cost simulation of hygro-thermo-mechanical (H-T-M) coupling problems in…

Numerical Analysis · Mathematics 2025-12-11 Hao Dong , Yifei Ding , Jiale Linghu , Yufeng Nie , Yaochuang Han

The hybrid tensor network (HTN) method is a general framework allowing for the construction of an effective wavefunction with the combination of classical tensors and quantum tensors, i.e., amplitudes of quantum states. In particular,…

Quantum Physics · Physics 2025-08-08 Hiroyuki Harada , Yasunari Suzuki , Bo Yang , Yuuki Tokunaga , Suguru Endo

Building on the standard hierarchy of pure states (HOPS) approach, we construct a generalized formulation suitable for open quantum systems interacting with nonstationary Gaussian baths, potentially extending its applicability to…

Quantum Physics · Physics 2026-03-13 Vladislav Sukharnikov , Stasis Chuchurka , Frank Schlawin

In this work, we present the tree tensor network Nystr\"om (TTNN), an algorithm that extends recent research on streamable tensor approximation, such as for Tucker and tensor-train formats, to the more general tree tensor network format,…

Numerical Analysis · Mathematics 2024-12-10 Alberto Bucci , Gianfranco Verzella

Being able to describe accurately the dynamics and steady-states of driven and/or dissipative but quantum correlated lattice models is of fundamental importance in many areas of science: from quantum information to biology. An efficient…

Quantum Physics · Physics 2021-05-19 Conor Mc Keever , Marzena H. Szymańska

In power system dynamic simulation, up to 90% of the computational time is devoted to solve the network equations, i.e., a set of linear equations. Traditional approaches are based on sparse LU factorization, which is inherently sequential.…

Systems and Control · Electrical Eng. & Systems 2021-07-06 Lu Zhang , Bin Wang , Vivek Sarin , Weiping Shi , P. R. Kumar , Le Xie

We derive the formula of energy flux for the hierarchical equations of motion (HEOM) method with the help of stochastic decoupling technique. The resulting expression is a combination of the terms in the first two layers of the hierarchy.…

Statistical Mechanics · Physics 2019-04-30 Yun Zhou , Tie-Jun Xiao , Jun Cao , Yun-An Yan