ITensor Library Classes and Methods

Detailed information about every method and function in the ITensor library.

The documentation may omit minor details that do not change how you use a method, like describing a particular function as f(ITensor T) even though its actual signature is f(ITensor const& T).

Utilities

• Reading and Writing Objects to Disk

• Support for MPI (Message Passing Interface) Parallelism

• Support for working with lattices:

  • LatticeBond Objects
  • Functions for Making Lattices

• BondGate - type for making quantum circuits or time-evolution gates

Index

• Index. Tensor index.

• Special Index modes:

  • QN Index. Index carrying QN block information.

• IndexVal. Index-value pair.

• IndexSet. Container for storing indices.

• QN. Abelian quantum numbers.

ITensor

• ITensor. The elementary tensor type.
  

• Sparse ITensors:

  • QN ITensor
  • Single Element ITensor
  • Combiner
  • Delta and Diagonal ITensor

• Tensor Decompositions. Singular value decomposition, density matrix diagonalization, etc.

Matrix product states (MPS) and matrix product operators (MPO)

• SiteSet. Collection of site objects, defining a Hilbert space and local operators.
  

  • SpinHalf and SpinHalfSite. S=1/2 spin sites.
    
  • SpinOne and SpinOneSite. S=1 spin sites.
    
  • Boson and BosonSite. Spinless boson sites with adjustable max occupancy.
    
  • Fermion and FermionSite. Spinless fermion sites.
    
  • Electron and ElectronSite. Spinful fermion sites.
    
  • tJ and tJSite. t-J model sites.
    
  • CustomSpin and CustomSpinSite. Spin sites with custom spin S size.
    

• InitState. Helper object for initializing product-state MPS.
  

• MPS. Matrix product state class.
  

• MPO. Matrix product operator class.
  

• Algorithms for MPS and MPO.
  

• AutoMPO. System for making MPOs from sums of local operators.
  

• Time Evolution of MPS. Methods for time evolving MPS.

Density matrix renormalization group (DMRG)

• Sweeps. Class for specifying DMRG accuracy parameters.

• DMRG. Interface for running DMRG calculations.