Calculate dynamic correlation function for fermonic operators in ITensor

DMRG and Numerical Methods
1

Hi,
I would like to calculate the dynamic correlation function, e.g., \langle c(t)c^{\dagger}(0)\rangle for fermionic operators by ITensor. Standard way to this using time evolution is

  1. calculate the groundstate |\psi_g\rangle
  2. act c^\dagger on |\psi_g\rangle
  3. time evolution on c^\dagger|\psi_g\rangle and obtain e^{-iHt} c^\dagger|\psi_g\rangle
  4. overlap with c^\dagger|\psi_g\rangle and multiply the phase factor e^{iE_g t}.

I first try define an MPO by AutoMPO for c^\dagger but it raises an error

Parity-odd fermionic terms not yet supported by OpSum to MPO conversion

So what is the correct way to do this? A possible way is to naively use op("Cdag",sites[i]) (sites[i] is an Index) and then using apply to act it on |\psi_g\rangle but creation/annihilation operators should be attached with an Jordan-Wigner string and I do not know if apply correctly treat this.
Thanks!

2

I find that in Proper way to construct fermion gates Mile’s reply mentioned that the apply function will automatically deal with the fermion string so maybe this should be the correct way.

3

This topic was automatically closed 10 days after the last reply. New replies are no longer allowed.