Measures of operator entanglement of two-qubit gates
S. Balakrishnan, R. Sankaranarayanan · Physical Review A · 2011
Two different measures of operator entanglement of two-qubit gates, namely, Schmidt strength and linear entropy, are studied. While these measures are shown to have a one-to-one relation between them for the Schmidt number 2 class of gates, no such relation exists for the Schmidt number 4 class, implying that the measures are inequivalent in general. Further, we establish a simple relation between linear entropy and local invariants of two-qubit gates. The implication of the relation is discussed.