Hi,
I am aware that the mps codes can measure correlations with more than two operators, but it seems this is not supported in sparsediag codes. For example, when I enter
'MEASURE_CORRELATIONS[S3]':'Sz:Sz:Sz'
and run sparsediag for a Heisenberg model, an error shows
"Cannot evaluate expression - 0.5 * Sz:Sz(i)"
Is there a way to compute this in ED? If this is not possible, I would like to know which part of the source codes of alps to modify so as to implement this myself.