openfermion.measurements.pair_within

Generates pairings of labels that contain each pair at least once.

A pairing of a list is a set of pairs of list elements. E.g. a pairing of

labels = [1, 2, 3, 4, 5, 6, 7, 8]

could be

[(1, 2), (3, 4), (5, 6), (7, 8)]

(Note that we insist each element only appears in a pairing once; the following is not a pairing:

[(1, 1), (2, 2), (3, 4), (5, 6), (7, 8)]

This function generates a set of len(labels)-1 such pairings of the input list labels, such that each element in labels is paired with each other element in at least one pairing

labels list

list of elements

pairings list

list of pairings of elements of labels