The creation/annihilation operators are obtained directly from the difference matrix, let's denote it by symbol: B. Suppose we suppose a particular matrix-element with indices: I and J . Then the pair-difference, δ, is just an array with "-1", "0", and "1" elements. The "-1" element indicates a loss of an electron from a given orbital, i.e. an annihilation, while "1" indicates a creation of an electron into a given orbital (and "0" indicates no change):