QuSpin: a Python Package for Dynamics and Exact Diagonalisation of Quantum Many Body Systems part I: spin chains

TL;DR

QuSpin is an open-source Python package designed for exact diagonalization and quantum dynamics simulations of spin chains, supporting various symmetries and enabling studies of complex many-body phenomena.

Contribution

It introduces a user-friendly Python toolkit that supports advanced symmetry usage and dynamic simulations for spin chains up to 32 sites, with detailed usage examples.

Findings

Supports quantum quenches, ETH, MBL, and dynamical phase transitions.

Enables simulation of Floquet systems and adiabatic ramps.

Facilitates studies of spin-photon interactions.

Abstract

We present a new open-source Python package for exact diagonalization and quantum dynamics of spin(-photon) chains, called QuSpin, supporting the use of various symmetries in 1-dimension and (imaginary) time evolution for chains up to 32 sites in length. The package is well-suited to study, among others, quantum quenches at finite and infinite times, the Eigenstate Thermalisation hypothesis, many-body localisation and other dynamical phase transitions, periodically-driven (Floquet) systems, adiabatic and counter-diabatic ramps, and spin-photon interactions. Moreover, QuSpin's user-friendly interface can easily be used in combination with other Python packages which makes it amenable to a high-level customisation. We explain how to use QuSpin using four detailed examples: (i) Standard exact diagonalisation of XXZ chain (ii) adiabatic ramping of parameters in the many-body localised XXZ model, (iii) heating in the periodically-driven transverse-field Ising model in a parallel field, and (iv) quantised light-atom interactions: recovering the periodically-driven atom in the semi-classical limit of a static Hamiltonian.