Dear All,
ITensor provides a function that computes correlation function matrix for two operators A_{i}, B_{i}.
That is C[i, j] = correlation_matrix(psi, A_{i}, B_{i}).
How can I compute a multi-point correlation quantity, for instance, C[i, j, k, l]?
Could you please help me with this? also how to implement it using DMRGObserver?
And I apologize for asking the naive question.
There is unfortunately limited support for general C_ijkl, but some things are implemented in this package:
Thanks you so much for the quick response
Also, Zahid, if you are interested in a way to implement multi-point correlators yourself (say of the form \langle\psi| A_i B_j C_k |\psi\rangle), one thing you can try is to first multiply A_i into your state |\psi'_i\rangle = A_i |\psi\rangle, then compute a kind of “mixed correlator” \langle\psi| B_j C_k |\psi'_i\rangle for all j and k for a fixed i, then repeat for different values of i.
Our correlation_matrix function does not support putting different states around the operators, so you would have to also implement the two-point correlator part of that strategy above yourself. Hope that’s helpful to think about –
Nice! Thanks for your response. Sure, I will try this strategy.
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