MPS & MPOs as a function of a for loop variable

Question

Hi Miles,
I am trying to get the ground state of a Hamiltonian, which depends on an external field strength, say 'h'. Now I want to vary h in a for loop and get the corresponding ground state. But I don't know how to treat the ITensor MPO or MPS as a function of a loop variable, something like psi(h), can this be done?

Thanking You,
Ipsita.

Answer 1

Hi Ipsita,
The direct answer to your question is that, whichever procedure you are using to make your MPO necessarily includes "h" as a parameter. (Say using AutoMPO, where "h" appears as a coefficient.) So then to change h, you just re-create the MPO again from the beginning, using a different value for h.

However, the other answer I would give to your question is to say, I don't recommend doing a lot of different calculations (I assume DMRG?) in a loop. Instead, I think it's a much better practice to do each calculation separately, and carefully study each one. How well did it go? Were all indications that it converged? Is the system approaching a phase boundary where perhaps the initial state and number of sweeps needed for convergence might need to be changed?

Best regards,
Miles

Comments

Hi, Thank you very much for your suggestion. Yes, it is DMRG that I was talking about.