## Learn to Use ITensor

# The ITensor Book

Tensor methods are a powerful approach for problems in physics and applied mathematics, but keeping track of tensor indices can be tedious and error-prone.

Inspired by tensor diagram notation, ITensor automatically handles low-level details of index ordering and data permutation, freeing the user to think about the structure of tensor networks. Indices in ITensor carry extra information and "multiplying" two ITensors contracts all matching indices, similar to Einstein summation. Despite these higher level features ITensor is very efficient.

The goal of this book is to quickly familiarize users with the main features of ITensor. Later chapters turn to advanced features and customizing higher-level parts of the library.

# Table of Contents

### ITensor Fundamentals

### IQTensor: Block-Sparse, Quantum Number Conserving Tensors

### Matrix Product States and DMRG

### Design of ITensor Library and Internals

*The ITensor Book is written and maintained by Miles Stoudenmire*

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