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We present a numerically exact Inchworm Monte Carlo method for equilibrium multiorbital quantum impurity problems with general interactions and hybridizations. We show that the method, originally developed to overcome the dynamical sign…

Strongly Correlated Electrons · Physics 2020-05-25 Eitan Eidelstein , Emanuel Gull , Guy Cohen

We extend finite-temperature tensor network methods to compute Matsubara imaginary-time correlation functions, building on the minimally entangled typical thermal states (METTS) and purification algorithms. While imaginary-time correlation…

Strongly Correlated Electrons · Physics 2022-05-18 Daniel Bauernfeind , Xiaodong Cao , E. Miles Stoudenmire , Olivier Parcollet

We present a unified framework for renormalization group methods, including Wilson's numerical renormalization group (NRG) and White's density-matrix renormalization group (DMRG), within the language of matrix product states. This allows…

Strongly Correlated Electrons · Physics 2009-10-14 A. Weichselbaum , F. Verstraete , U. Schollwöck , J. I. Cirac , Jan von Delft

Strongly correlated quantum impurity problems appear in a wide variety of contexts ranging from nanoscience and surface physics to material science and the theory of strongly correlated lattice models, where they appear as auxiliary systems…

Strongly Correlated Electrons · Physics 2013-02-19 Hartmut Hafermann , Philipp Werner , Emanuel Gull

The impurity Green's function Gf in the local non-Fermi liquid state is evaluated by means of the continuous-time quantum Monte Carlo method extended to the multichannel Anderson model. For N=M (where N and M are numbers of spin components…

Strongly Correlated Electrons · Physics 2015-05-20 Junya Otsuki

We introduce real-time density matrix embedding theory (DMET), a dynamical quantum embedding theory for computing non-equilibrium electron dynamics in strongly correlated systems. As in the previously developed static DMET, real-time DMET…

Chemical Physics · Physics 2017-11-03 Joshua S. Kretchmer , Garnet Kin-Lic Chan

Based on the process tensor framework, we extend the time-evolving matrix product operator (TEMPO) method to solve bosonic quantum impurity problems (QIPs) with off-diagonal system-bath coupling. Our method is a most generic extension of…

Mesoscale and Nanoscale Physics · Physics 2026-04-03 Chu Guo , Wei Wu , Xiansong Xu , Tian Jiang , Ping-Xing Chen , Ruofan Chen

Using an imaginary-time matrix-product state (MPS) based quantum impurity solver we perform a realistic dynamical mean-field theory (DMFT) calculation combined with density functional theory (DFT) for Sr$_2$RuO$_4$. We take the full…

Strongly Correlated Electrons · Physics 2020-01-22 Nils-Oliver Linden , Manuel Zingl , Claudius Hubig , Olivier Parcollet , Ulrich Schollwöck

We describe two developments of tensor network influence functionals (in particular, influence functional matrix product states (IF-MPS)) for quantum impurity dynamics within the fermionic setting of the Anderson impurity model. The first…

Strongly Correlated Electrons · Physics 2024-07-03 Gunhee Park , Nathan Ng , David R. Reichman , Garnet Kin-Lic Chan

We propose an efficient algorithm to numerically solve Anderson impurity problems using matrix product states. By introducing a modified chain mapping we obtain significantly lower entanglement, as compared to all previous attempts, while…

Strongly Correlated Electrons · Physics 2021-07-14 Lucas Kohn , Giuseppe E. Santoro

This paper presents iterative methods for solving tensor equations involving the T-product. The proposed approaches apply tensor computations without matrix construction. For each initial tensor, these algorithms solve related problems in a…

Numerical Analysis · Mathematics 2025-04-28 Malihe Nobakht Kooshkghazi , Salman Ahmadi-Asl , Hamidreza Afshin

On the basis of the Green function method, analytical solutions of the diffusion equation which describes nonstationary migration of nonequilibrium interstitial impurity atoms have been derived. It is supposed that the initial distribution…

Materials Science · Physics 2008-09-09 O. I. Velichko , O. N. Burunova

We introduce a quantum Monte Carlo technique to calculate exactly at finite temperatures the Green function of a fermionic quantum impurity coupled to a bosonic field. While the algorithm is general, we focus on the single impurity Anderson…

Mesoscale and Nanoscale Physics · Physics 2009-11-11 Liliana Arrachea , Marcelo J. Rozenberg

Tensor networks have historically proven to be of great utility in providing compressed representations of wave functions that can be used for calculation of eigenstates. Recently, it has been shown that a variety of these networks can be…

Quantum Physics · Physics 2024-06-25 Amartya Bose

We solve the nonequilibrium dynamical mean-field theory (DMFT) using matrix product states (MPS). This allows us to treat much larger bath sizes and by that reach substantially longer times (factor $\sim$ 2 -- 3) than with exact…

Strongly Correlated Electrons · Physics 2014-12-22 F. Alexander Wolf , Ian P. McCulloch , Ulrich Schollwöck

We implement an efficient numerical method to calculate response functions of complex impurities based on the Density Matrix Renormalization Group (DMRG) and use it as the impurity-solver of the Dynamical Mean Field Theory (DMFT). This…

Strongly Correlated Electrons · Physics 2017-11-27 Y. Núñez Fernández , K. Hallberg

Dynamical mean-field theory (DMFT) is a useful tool to analyze models of strongly correlated fermions like the Hubbard model. In DMFT, the lattice of the model is replaced by a single impurity site embedded in an effective bath. The…

Quantum Physics · Physics 2026-03-27 Stefan Wolf , Martin Eckstein , Michael J. Hartmann

A continuous-time path integral Quantum Monte Carlo method using the directed-loop algorithm is developed to simulate the Anderson single-impurity model in the occupation number basis. Although the method suffers from a sign problem at low…

Strongly Correlated Electrons · Physics 2009-11-10 Jaebeom Yoo , Shailesh Chandrasekharan , Harold U. Baranger

We derive equations of motion for Green's functions of the multi-orbital Anderson impurity model by differentiating symmetrically with respect to all time arguments. The resulting equations relate the one- and two-particle Green's function…

Strongly Correlated Electrons · Physics 2019-08-14 Josef Kaufmann , Patrik Gunacker , Alexander Kowalski , Giorgio Sangiovanni , Karsten Held

The three key elements of a quantum simulation are state preparation, time evolution, and measurement. While the complexity scaling of time evolution and measurements are well known, many state preparation methods are strongly…

Quantum Physics · Physics 2022-03-24 Trevor Keen , Bo Peng , Karol Kowalski , Pavel Lougovski , Steven Johnston