Quantifying interference in multipartite quantum systems

TL;DR

This paper investigates quantum interference in multi-qubit systems, introduces a new quantum correlation measure called quantum interference, and reveals that entanglement is not necessary for multiparticle interference.

Contribution

It establishes a new type of quantum correlation called quantum interference and provides explicit quantifiers based on the density matrix elements.

Findings

Quantum interference can occur without entanglement.

New quantifiers for quantum interference are derived.

Entanglement is not essential for multiparticle interference.

Abstract

The characterization of quantum correlations is crucial to the development of new quantum technologies and to understand how dramatically quantum theory departs from classical physics. Here we systematically study single- and multiparticle interference patterns produced by general two- and three-qubit systems. From this we establish on phenomenological grounds a new type of quantum correlation for these systems, which we name quantum interference, deriving some quantifiers that are given explicitly in terms of the density matrix elements of the complete system. By using these quantifiers, we show that, contrary to our expectations, entanglement is not a required property for a composite quantum system to manifest multiparticle interference.