4-site/2-bond measurements:
non-local singlet correlations (from which extended s-wave and d-wave susceptibilities can be derived)
projected charge correlations (from which raman susceptibilities can be derived)
current-current correlations
full 4-pt greens function for bethe-salpeter stuff?
unequal time greens functions and measurements
4-site/2-bond measurements: non-local singlet correlations (from which extended s-wave and d-wave susceptibilities can be derived) projected charge correlations (from which raman susceptibilities can be derived) current-current correlations
full 4-pt greens function for bethe-salpeter stuff?