QuTree: A tree tensor network package

Roman Ellerbrock; K Grace Johnson; Stefan Seritan; Hannes Hoppe; J H Zhang; Tim Lenzen; Thomas Weike; Uwe Manthe; Todd J Martínez

doi:10.1063/5.0180233

QuTree: A tree tensor network package

J Chem Phys. 2024 Mar 21;160(11):112501. doi: 10.1063/5.0180233.

Authors

Roman Ellerbrock^{1

2

3}, K Grace Johnson^{1

2}, Stefan Seritan^{1

2}, Hannes Hoppe³, J H Zhang^{1

2}, Tim Lenzen³, Thomas Weike³, Uwe Manthe³, Todd J Martínez^{1

2}

Affiliations

¹ Department of Chemistry and The PULSE Institute, Stanford University, Stanford, California 94305, USA.
² SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA.
³ Bielefeld University, Universitätsstraße 25, 33615 Bielefeld, Germany.

PMID: 38497471
DOI: 10.1063/5.0180233

Abstract

We present QuTree, a C++ library for tree tensor network approaches. QuTree provides class structures for tensors, tensor trees, and related linear algebra functions that facilitate the fast development of tree tensor network approaches such as the multilayer multiconfigurational time-dependent Hartree approach or the density matrix renormalization group approach and its various extensions. We investigate the efficiency of relevant tensor and tensor network operations and show that the overhead for managing the network structure is negligible, even in cases with a million leaves and small tensors. QuTree focuses on providing simple, high-level routines while retaining easy access to the backend to facilitate novel developments. We demonstrate the capabilities of the package by computing the eigenstates of coupled harmonic oscillator Hamiltonians and performing random circuit simulations on a virtual quantum computer.