Coherence makes quantum systems ‘magical’

Abstract

Two primary facets of quantum technological advancement that hold great promise are quantum communication and quantum computation. For quantum communication, the canonical resource is entanglement. For quantum gate implementation, the resource is ‘magic’ in an auxiliary system. It has already been shown that quantum coherence is the fundamental resource for the creation of entanglement. We argue on the similar spirit that quantum coherence is the fundamental resource when it comes to the creation of ‘magic’. This unifies the two strands of modern development in quantum technology under the common underpinning of existence of quantum superposition, quantified by the coherence in quantum theory. We also obtain a coherence monotone from the discrete Wigner distribution. We further study the interplay between quantum coherence and ‘magic’ in a qutrit system and that between quantum entanglement and ‘magic’ in a qutrit-qubit setting.