Volume 964
Lecture Notes in Physics
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Shi-Ju Ran, Emanuele Tirrito, Cheng Peng, Xi Chen, Luca Tagliacozzo, Gang Su and Maciej Lewenstein

Tensor Network Contractions

Methods and Applications to Quantum Many-Body Systems

Shi-Ju Ran
Department of Physics, Capital Normal University, Beijing, China
Emanuele Tirrito
Quantum Optics Theory, Institute of Photonic Sciences, Castelldefels, Spain
Cheng Peng
Stanford Institute for Materials and Energy Sciences, SLAC and Stanford University, Menlo Park, CA, USA
Xi Chen
School of Physical Sciences, University of Chinese Academy of Science, Beijing, China
Luca Tagliacozzo
Department of Quantum Physics and Astrophysics, University of Barcelona, Barcelona, Spain
Gang Su
Kavli Institute for Theoretical Sciences, University of Chinese Academy of Science, Beijing, China
Maciej Lewenstein
Quantum Optics Theory, Institute of Photonic Sciences, Castelldefels, Spain
ISSN 0075-8450e-ISSN 1616-6361
Lecture Notes in Physics
ISBN 978-3-030-34488-7e-ISBN 978-3-030-34489-4
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Preface

Tensor network (TN), a young mathematical tool of high vitality and great potential, has been undergoing extremely rapid developments in the last two decades, gaining tremendous success in condensed matter physics, atomic physics, quantum information science, statistical physics, and so on. In this lecture notes, we focus on the contraction algorithms of TN as well as some of the applications to the simulations of quantum many-body systems. Starting from basic concepts and definitions, we first explain the relations between TN and physical problems, including the TN representations of classical partition functions, quantum many-body states (by matrix product state, tree TN, and projected entangled pair state), time evolution simulations, etc. These problems, which are challenging to solve, can be transformed to TN contraction problems. We present then several paradigm algorithms based on the ideas of the numerical renormalization group and/or boundary states, including density matrix renormalization group, time-evolving block decimation, coarse-graining/corner tensor renormalization group, and several distinguished variational algorithms. Finally, we revisit the TN approaches from the perspective of multi-linear algebra (also known as tensor algebra or tensor decompositions) and quantum simulation. Despite the apparent differences in the ideas and strategies of different TN algorithms, we aim at revealing the underlying relations and resemblances in order to present a systematic picture to understand the TN contraction approaches.

Shi-Ju Ran
Emanuele Tirrito
Cheng Peng
Xi Chen
Luca Tagliacozzo
Gang Su
Maciej Lewenstein
Beijing, ChinaCastelldefels, SpainMenlo Park, CA, USABeijing, ChinaBarcelona, SpainBeijing, ChinaCastelldefels, Spain
Acknowledgements

We are indebted to Mari-Carmen Bañuls, Ignacio Cirac, Jan von Delft, Yichen Huang, Karl Jansen, José Ignacio Latorre, Michael Lubasch, Wei Li, Simone Montagero, Tomotoshi Nishino, Roman Orús, Didier Poilblanc, Guifre Vidal, Andreas Weichselbaum, Tao Xiang, and Xin Yan for helpful discussions and suggestions. SJR acknowledges Fundació Catalunya-La Pedrera, Ignacio Cirac Program Chair and Beijing Natural Science Foundation (Grants No. 1192005). ET and ML acknowledge the Spanish Ministry MINECO (National Plan 15 Grant: FISICATEAMO No. FIS2016-79508-P, SEVERO OCHOA No. SEV-2015-0522, FPI), European Social Fund, Fundació Cellex, Generalitat de Catalunya (AGAUR Grant No. 2017 SGR 1341 and CERCA/Program), ERC AdG OSYRIS and NOQIA, EU FETPRO QUIC, and the National Science Centre, Poland-Symfonia Grant No. 2016/20/W/ST4/00314. LT was supported by the Spanish RYC-2016-20594 program from MINECO. SJR, CP, XC, and GS were supported by the NSFC (Grant No. 11834014). CP, XC, and GS were supported in part by the National Key R&D Program of China (Grant No. 2018FYA0305800), the Strategic Priority Research Program of CAS (Grant No. XDB28000000), and Beijing Municipal Science and Technology Commission (Grant No. Z118100004218001).

Acronyms
AKLT state

Affleck–Kennedy–Lieb–Tasaki state

AOP

Ab initio optimization principle

CANDECOMP/PARAFAC

Canonical decomposition/parallel factorization

CFT

Conformal field theory

CTM

Corner transfer matrix

CTMRG

Corner transfer matrix renormalization group

DFT

Density functional theory

DMFT

Dynamical mean-field theory

DMRG

Density matrix renormalization group

ECTN

Exactly contractible tensor network

HOOI

Higher-order orthogonal iteration

HOSVD

Higher-order singular value decomposition

HOTRG

Higher-order tensor renormalization group

iDMRG

Infinite density matrix renormalization group

iPEPO

Infinite projected entangled pair operator

iPEPS

Infinite projected entangled pair state

iTEBD

Infinite time-evolving block decimation

MERA

Multiscale entanglement renormalization ansatz

MLA

Multi-linear algebra

MPO

Matrix product operator

MPS

Matrix product state

NCD

Network contractor dynamics

NP hard

Non-deterministic polynomial hard

NRG

Numerical renormalization group

NTD

Network Tucker decomposition

PEPO

Projected entangled pair operator

PEPS

Projected entangled pair state

QES

Quantum entanglement simulation/simulator

QMC

Quantum Monte Carlo

RG

Renormalization group

RVB

Resonating valence bond

SEEs

Self-consistent eigenvalue equations

SRG

Second renormalization group

SVD

Singular value decomposition

TDVP

Time-dependent variational principle

TEBD

Time-evolving block decimation

TMRG

Transfer matrix renormalization group

TN

Tensor network

TNR

Tensor network renormalization

TNS

Tensor network state

TPO

Tensor product operator

TRD

Tensor ring decomposition

TRG

Tensor renormalization group

TTD

Tensor-train decomposition

TTNS

Tree tensor network state

VMPS

Variational matrix product state

Contents
Index 149