The problem of finding the resource-free, closest local unitary, to any bipartite unitary gate U is addressed. Previously discussed as a measure of nonlocality, the distance KD(U) to the nearest product unitary has implications for circuit complexity and related quantities. Dual unitaries, currently of great interest in models of complex quantum many-body systems, are shown to have a preferred role as these are maximally and equally away from the set of local unitaries.
