ITensorTDMPO.jl

ITensorTDMPO.jl provides time evolution for time-dependent Hamiltonians on top of ITensorMPS.jl — in particular, adiabatic ramps.

The Hamiltonian is described once, as a set of driving channels H(t) = Σₐ fₐ(t) H⁽ᵃ⁾, and a single entry point, time_evolve, selects among several integrators (piecewise-constant TDVP, the Dyson series, the Magnus expansion, and a commutator-free exponential propagator), plus adaptive step-size control, imaginary time, and adiabaticity diagnostics. The Dyson and Magnus constructions implement part of the algorithms of Vanthilt, Van Damme, Haegeman, McCulloch & Vanderstraeten (2025).

Registered in the Julia General registry; not affiliated with the ITensor project.

Installation

using Pkg
Pkg.add("ITensorTDMPO")

Documentation

The full documentation — every algorithm, benchmark, and the API reference — is at jaydevsr.github.io/ITensorTDMPO.jl.

To build it locally instead:

julia --project=docs -e 'using Pkg; Pkg.develop(path="."); Pkg.instantiate(); include("docs/make.jl")'

then open docs/build/index.html.

Quick example

using ITensorMPS, ITensorTDMPO

ramp = Ramp(SmoothstepRamp(), 0.0, 10.0, 0.0, 2.0)

ψ = time_evolve([(1.0, Hzz), (ramp, Hx)], ψ0, 0.0, 10.0;
                nsteps = 100, cutoff = 1e-10, maxdim = 128)

Testing

julia --project=. -e 'using Pkg; Pkg.test()'

Citation

If you use the Dyson or Magnus constructions, please cite the paper this package implements:

@article{Vanthilt2025,
  title   = {Matrix Product Operator Encodings of the Magnus Expansion and Dyson Series},
  author  = {Vanthilt, Victor and Van Damme, Maarten and Haegeman, Jutho and McCulloch, Ian P. and Vanderstraeten, Laurens},
  journal = {arXiv preprint arXiv:2605.21597},
  year    = {2025},
}

The commutator-free propagator (alg = "cfet") implements the scheme of:

@article{AlvermannFehske2011,
  title   = {High-order commutator-free exponential time-propagation of driven quantum systems},
  author  = {Alvermann, Andreas and Fehske, Holger},
  journal = {Journal of Computational Physics},
  volume  = {230},
  pages   = {5930--5956},
  year    = {2011},
  doi     = {10.1016/j.jcp.2011.04.006},
}