Difficulty with simulating a specific model with VUMPS (that works perfectly fine with regular DMRG)

[ryanlevy]

@amoghanakru

Is there any way I can import MPS’s from open chain DMRG computations

There is limited functionality here unfortunately (there is a bit of a question of how to take a finite MPS and make it into a uniform state). Matt has added something to attempt this

ITensor/ITensorInfiniteMPS.jl/blob/main/examples/development/finite_mps_to_infinite_mps.jl#L44

However last time I tried this I don’t believe it had quantum numbers working (PRs welcome!)

@amoghanakru

or infinite MPS’s from prior VUMPS calculations (e.g. the output of something easy like the Fermi-Hubbard model), for use as VUMPS ansätze? I’ve been saving/loading MPS’s using HDF5 in open-chain DMRG but I’m not sure how this functionality transfers over to VUMPS/InfiniteMPS.

The same save/load functionality exists here as well. Here’s an example on saving loading

using HDF5
using ITensorInfiniteMPS
using ITensorMPS

# do stuff to get a state
psi = ...
h5open("my_wavefunction.h5","w") do fo
  write(fo,"psi",psi)
  # example metadata, needs vector for hdf5 conversion
  write(fo, "model_params", [model_params]) 
end

#######

psi, model_params = h5open("my_wavefunction.h5","r") do fi
  read(fi,"psi",InfiniteCanonicalMPS), read(fi,"model_params")[1]
end
s = siteinds(psi) 

model = #...
# load H using matching indices from old calculation
H = InfiniteSum{localham_type}(model, s; model_params...)