XDiag (formerly exactdiag)

Official Resources

• Homepage: https://awietek.github.io/xdiag/
• Source Repository: https://github.com/awietek/xdiag
• Documentation: https://awietek.github.io/xdiag/
• Julia Package: https://github.com/awietek/XDiag.jl
• License: Apache License 2.0

Overview

XDiag (previously known as exactdiag) is a modern, high-performance C++ library for the Exact Diagonalization (ED) of quantum many-body systems. It is designed to be user-friendly while maintaining high efficiency. It provides a Julia interface (XDiag.jl) which makes it accessible for rapid prototyping and scripting. It specializes in spin systems, t-J models, and Hubbard models.

Scientific domain: Quantum Many-Body Physics, Exact Diagonalization
Target user community: Theoretical Physicists, Condensed Matter Researchers

Capabilities (CRITICAL)

• Models: Heisenberg, t-J, Hubbard, and various custom spin/fermion Hamiltonians.
• Symmetries: Utilization of translation, point group, and spin symmetries to reduce Hilbert space dimension.
• Algorithms:
  • Full diagonalization (Lapack)
  • Iterative diagonalization (Lanczos) for ground state and low-lying excited states.
  • Time evolution.
  • Finite temperature calculations (typicality).
• Interfaces: C++17 library and a rich Julia interface.
• Parallelism: Shared memory parallelization (OpenMP) and distributed memory (MPI).

Inputs & Outputs

• Input formats: Hamiltonian definition via API (C++ or Julia), lattice geometry.
• Output data types: Eigenenergies, eigenstates, correlation functions, spectral functions.

Performance Characteristics

• Highly optimized for modern architectures.
• Can handle Hilbert spaces up to ~50 billion states (with MPI).
• Efficient implementation of matrix-vector multiplications.

Application Areas

• Frustrated magnetism.
• Strongly correlated electron systems.
• Quantum phase transitions.
• Benchmarking quantum simulators.

Verification & Sources

• Source: Active GitHub repository (awietek/xdiag).
• Documentation: Comprehensive and modern.
• Identity: Confirmed renaming from exactdiag to XDiag.

Confidence: VERIFIED

Verification status: ✅ VERIFIED

• Website: ACTIVE
• Documentation: COMPREHENSIVE
• Source: OPEN (GitHub)
• Development: ACTIVE
• Applications: Exact Diagonalization