Support of fermionic systems

[diret47]

Hi.
Is it possible to compute fermionic PEPS?

[jurajHasik]

Hi,

currently fermionic iPEPS are not available out-of-the-box. What are the options:

One way of formulating iPEPS computations with fermions is in terms of Z2-symmetric block-sparse tensors
together with swap-gates realizing anticommutation rules. The basic ingredients for that, including AD support,
can be provided by YASTN - https://github.com/yastn/yastn
YASTN is already used here, in peps-torch, for implementation of abelian-symmetric iPEPS / CTM / observables / transfer matrices.

The YASTN also includes full implementation of (finite-temperature) Hubbard model, see

https://github.com/yastn/yastn/tree/master/yastn/tn/fpeps

So if you want to instead do AD-based optimizations, one can start from there, making use of CTM & observables. That's pretty much all you need for AD-optimization.

Alternatively, there are open-source fermionic TNs supported by i.e. QuantumGhent's TensorKit https://github.com/Jutho/TensorKit.jl (in Julia language)

[diret47]

Thank you very much for your reply.
https://github.com/yastn/yastn/tree/master/yastn/tn/fpeps Is this implementation based on simple update or full update?