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Due to the exponential growth of the state space of coupled quantum systems it is not possible, in general, to numerically store the state of a very large number of quantum systems within a classical computer. We demonstrate a method for…

Quantum Physics · Physics 2017-02-07 J. J. Bowen , V. M. Dwyer , I. W. Phillips , M. J. Everitt

We address the calculation of dynamical correlation functions for many fermion systems at zero temperature, using the auxiliary-field quantum Monte Carlo method. The two-dimensional Hubbard hamiltonian is used as a model system. Although…

Strongly Correlated Electrons · Physics 2016-08-24 Ettore Vitali , Hao Shi , Mingpu Qin , Shiwei Zhang

A method for deriving quantum kinetic equations with initial correlations is developed on the basis of the nonequilibrium Green's function formalism. The method is applicable to a wide range of correlated initial states described by…

Statistical Mechanics · Physics 2009-10-31 V. G. Morozov , G. Röpke

We introduce a unified Gaussian quantum operator representation for fermions and bosons. The representation extends existing phase-space methods to Fermi systems as well as the important case of Fermi-Bose mixtures. It enables simulations…

Other Condensed Matter · Physics 2009-11-11 P. D. Drummond , J. F. Corney

We introduce a novel computational framework for excited-states molecular quantum dynamics simulations driven by quantum computing-based electronic-structure calculations. This framework leverages the fewest-switches surface-hopping method…

Quantum Physics · Physics 2024-02-26 Anthony Gandon , Alberto Baiardi , Pauline Ollitrault , Ivano Tavernelli

We study nonequilibrium thermodynamics in a fermionic resonant level model with arbitrary coupling strength to a fermionic bath, taking the wide-band limit. In contrast to previous theories, we consider a system where both the level energy…

Mesoscale and Nanoscale Physics · Physics 2018-03-07 Patrick Haughian , Massimiliano Esposito , Thomas L. Schmidt

Quantization of electrodynamics in curved space-time in the Lorenz gauge and with arbitrary gauge parameter makes it necessary to study Green functions of non-minimal operators with variable coefficients. Starting from the integral…

Mathematical Physics · Physics 2007-05-23 Giuseppe Bimonte , Enrico Calloni , Luciano Di Fiore , Giampiero Esposito , Leopoldo Milano , Luigi Rosa

We study time-dependent quantum transport in a correlated model system by means of time-propagation of the Kadanoff-Baym equations for the nonequilibrium many-body Green function. We consider an initially contacted equilibrium system of a…

Mesoscale and Nanoscale Physics · Physics 2011-11-28 Petri Myöhänen , Adrian Stan , Gianluca Stefanucci , Robert van Leeuwen

The nonequilibrium Dyson (or Kadanoff-Baym) equation, which is an equation of motion with long-range memory kernel for real-time Green functions, underlies many numerical approaches based on the Keldysh formalism. In this paper we map the…

Strongly Correlated Electrons · Physics 2014-02-05 Karsten Balzer , Martin Eckstein

Time-dependent nonequilibrium Green's functions (TDNEGF) are shown to provide a flexible, effective tool for the description of quantum mechanical single particle scattering on a spatially localized, time-dependent potential. Focusing on…

Quantum Physics · Physics 2017-12-07 Peter Foldi

While the Landauer viewpoint constitutes a modern basis to understand nanoscale electronic transport and to realize first-principles implementations of the non-equilibrium Green's function (NEGF) formalism, seeking an alternative picture…

Mesoscale and Nanoscale Physics · Physics 2020-12-18 Juho Lee , Han Seul Kim , Yong-Hoon Kim

While general quantum many-body systems require exponential resources to be simulated on a classical computer, systems of non-interacting fermions can be simulated exactly using polynomially scaling resources. Such systems may be of…

Strongly Correlated Electrons · Physics 2019-12-18 Norbert Schuch , Bela Bauer

Non equilibrium Green's function methods are regularly used to calculate current and charge densities in nanoscale (both molecular and semiconductor) conductors under bias. This method is mainly used for ballistic conduction but may be…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 M. Paulsson

An efficient implementation of the nonequilibrium Green function (NEGF) method combined with the density functional theory (DFT) using localized pseudo-atomic orbitals (PAOs) is presented for electronic transport calculations of a system…

Mesoscale and Nanoscale Physics · Physics 2015-05-14 Taisuke Ozaki , Kengo Nishio , Hiori Kino

The electric conductance of a molecular junction is calculated by recasting the Keldysh formalism in Liouville space. Dyson equations for nonequilibrium many body Green's functions (NEGF) are derived directly in real (physical) time. The…

Quantum Physics · Physics 2007-05-23 U. Harbola , S. Mukamel

The non-Markovian collision integral is obtained on the base of the Kadanoff-Baym equations for Green functions in a form with allowance for small retardation effects. The collisional relaxation times and damping width of the giant…

Nuclear Theory · Physics 2014-11-18 V. A. Plujko , S. N. Ezhov , A. N. Gorbachenko , M. O. Kavatsyuk

Quantum computing offers promising new avenues for tackling the long-standing challenge of simulating the quantum dynamics of complex chemical systems, particularly open quantum systems coupled to external baths. However, simulating such…

Quantum Physics · Physics 2025-02-20 Xiaohan Dan , Eitan Geva , Victor S. Batista

Efficient classical simulation has matured to a critical component of the quantum computing stack, driving hardware validation, algorithm design, and the study of structured quantum dynamics. Lie-algebraic simulation ($\mathfrak{g}$-sim) is…

Quantum Physics · Physics 2026-04-21 Adelina Bärligea , Matthew L. Sims-Goh , Jakob S. Kottmann

Current quantum simulation experiments are starting to explore non-equilibrium many-body dynamics in previously inaccessible regimes in terms of system sizes and time scales. Therefore, the question emerges which observables are best suited…

Quantum Gases · Physics 2022-05-24 A. Bohrdt , S. Kim , A. Lukin , M. Rispoli , R. Schittko , M. Knap , M. Greiner , J. Léonard

In strongly correlated materials, interacting electrons are entangled and form collective quantum states, resulting in rich low-temperature phase diagrams. Notable examples include cuprate superconductors, in which superconductivity emerges…