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Magnetism and spin physics are true quantum mechanical effects and their description usually requires multi reference methods and is often hidden in the standard description of molecules in quantum chemistry. In this work we present a…

We study the relationship between one-dimensional fermion gas-impurity models and quantum dissipative systems, via the method of constructive bosonisation and unitary transformation. Starting from an anisotropic Coqblin-Schrieffer model, a…

Quantum Physics · Physics 2010-06-01 Sol H. Jacobsen , P. D. Jarvis

A quantum two-level system immersed in a sub-Ohmic bath experiences enhanced low-frequency quantum statistical fluctuations which render the nonequilibrium quantum dynamics highly non-Markovian. Upon using the numerically exact…

Statistical Mechanics · Physics 2022-09-20 Florian Otterpohl , Peter Nalbach , Michael Thorwart

We discuss, within the simplified context provided by the polymeric harmonic oscillator, a construction leading to a separable Hilbert space that preserves some of the most important features of the spectrum of the Hamiltonian operator.…

General Relativity and Quantum Cosmology · Physics 2016-08-11 J. Fernando Barbero G. , Tomasz Pawłowski , Eduardo J. S. Villaseñor

We present an approximation scheme based on selective Hilbert space truncation for characterizing non-thermal states of magnetic systems beyond spin-wave theory. We study applications to states that are inaccessible through linear spin-wave…

Strongly Correlated Electrons · Physics 2026-01-13 Wesley Roberts , Michael Vogl , Roderich Moessner , Gregory A. Fiete

We investigate the real-time dynamics of open quantum spin-$1/2$ or hardcore boson systems on a spatial lattice, which are governed by a Markovian quantum master equation. We derive general conditions under which the hierarchy of…

Quantum Physics · Physics 2016-07-08 Stephan Caspar , Florian Hebenstreit , David Mesterházy , Uwe-Jens Wiese

We propose a ground-state ansatz for the Ohmic spin-boson model that improves upon the variational treatment of Silbey and Harris for biased systems in the scaling limit. In particular, it correctly captures the smooth crossover behaviour…

Mesoscale and Nanoscale Physics · Physics 2012-06-13 Ahsan Nazir , Dara P. S. McCutcheon , Alex W. Chin

We use the general framework of summation-by-parts operators to construct conservative, energy-stable, and well-balanced semidiscretizations of two different nonlinear systems of dispersive shallow water equations with varying bathymetry:…

Numerical Analysis · Mathematics 2025-11-12 Joshua Lampert , Hendrik Ranocha

While the quantum regression theorem (QRT) is the standard tool for computing multi-time correlation functions in open quantum systems, it relies on system-bath separability and an environment that remains in equilibrium, assumptions that…

Quantum Physics · Physics 2026-04-16 Matias Bundgaard-Nielsen , Jake Iles-Smith

The connections between standard theoretical tools used to study open quantum systems can sometimes seem opaque. Whether it is a Lindblad master equation, the equation of motion for the Wigner function or a dissipative Keldysh action,…

Quantum Physics · Physics 2023-11-02 Alexander McDonald , Aashish A. Clerk

The paper contributes to an ongoing effort to extend the conformal bootstrap beyond its traditional focus on systems of four-point correlation functions. Recently, it was demonstrated that semidefinite programming can be used to formulate a…

High Energy Physics - Theory · Physics 2025-12-10 Sebastian Harris

By employing the spin-boson model in a dense limit of environmental modes, quantum entanglement and correlation of sub-Ohmic and Ohmic baths for dissipative quantum phase transitions are numerically investigated based on the variational…

Quantum Physics · Physics 2022-02-08 Xiaohui Qian , Zhe Sun , Nengji Zhou

We present a theoretical scheme to simulate quantum field theory in a discrete curved spacetime based on the Bose-Hubbard model describing a Bose-Einstein condensate trapped inside an optical lattice. Using the Bose-Hubbard Hamiltonian, we…

Quantum Physics · Physics 2017-12-04 F. Bemani , R. Roknizadeh , M. H. Naderi

We develop fast and memory efficient numerical methods for learning functions of many variables that admit sparse representations in terms of general bounded orthonormal tensor product bases. Such functions appear in many applications…

Numerical Analysis · Mathematics 2020-05-11 Bosu Choi , Mark Iwen , Felix Krahmer

A recent promising arena for quantum advantage is simulating exponentially large classical systems. Here, we show how this advantage can be used to calculate the dynamics of open classical systems experiencing dissipation, including the…

Quantum Physics · Physics 2025-03-17 Agi Villanyi , Yariv Yanay , Ari Mizel

Hyperspectral measurements from long range sensors can give a detailed picture of the items, materials, and chemicals in a scene but analysis can be difficult, slow, and expensive due to high spatial and spectral resolutions of…

Machine Learning · Computer Science 2023-10-10 Michael G. Rawson , Timothy Doster

Open quantum systems host a wide range of intriguing phenomena, yet their simulation on well-controlled quantum devices is challenging, owing to the exponential growth of the Hilbert space and the inherently non-unitary nature of the…

We investigate on the procedure of extracting a "spectral density" from mixed QM/MM calculations and employing it in open quantum systems models. In particular, we study the connection between the energy gap correlation function extracted…

Quantum Physics · Physics 2012-12-12 Stéphanie Valleau , Alex Eisfeld , Alán Aspuru-Guzik

We provide a new approach to open quantum systems which is based on the Feshbach projection method in an appropriate Hilbert space. Instead of looking for a master equation for the dynamical map acting in the space of density operators we…

Quantum Physics · Physics 2013-08-14 Dariusz Chruściński , Andrzej Kossakowski

Some of the exciting phenomena uncovered in strongly correlated systems in recent years - for instance quantum topological order, deconfined quantum criticality, and emergent gauge symmetries -- appear in systems in which the Hilbert space…

Strongly Correlated Electrons · Physics 2019-08-07 Attila Szabó , Garry Goldstein , Claudio Castelnovo , Alexei M. Tsvelik