IDMRG implementation (tensor diagrams)

Question

Hi everyone,
i don't want to use the idmrg implementation as a black box, i want to implement my self in order to understand better the method. But i haven't found any document or tensor diagrams that explain how this is implemented. I have read all the review papers and White's papers, but i need some references how this is best implemented using iTensor.

Any help will be much appreciated.

Answer 1

Hi, so the ITensor iDMRG code is based on this paper by McCulloch:
https://arxiv.org/abs/0804.2509

It follows the main steps of the algorithm, but uses a different (yet equivalent) form of the growing step / ansatz for the new unit cell.

An alternative approach to infinite DMRG which you might be interested in implementing instead, since it can give much faster convergence for challenging systems, is the "VUMPS" algorithm described in this paper:
https://arxiv.org/abs/1701.07035