I am working with a Heisenberg spin-1 AF chain, trying to get the out-of-time correlators for z-components of the spins at different sites so that I can construct the spectral function. More explicitly, I am trying to calculate objects of the form

$$

e^{i E_0 t} <0|S^z_i e^{-i H t} S^z_j |0>

$$

In the correlators example http://itensor.org/docs.cgi?page=tutorials/correlations the MPS are turned into ITensor objects so that indices can be contracted. However, we can only time evolve MPS (I am using FitApplyMPO). I need to apply Sz_j before time evolving.. How can I accomplish this? I keep on getting errors.

Thanks so much for your help!