Device-independent tomography of multipartite quantum states

TL;DR

This paper introduces a method for device-independent tomography of multipartite quantum states, allowing state characterization solely from observed data without assuming perfect measurement devices, using self-testing based on Bell violations.

Contribution

It develops a black box tomography approach for multipartite states leveraging Bell violations, removing the need for device trust in quantum state characterization.

Findings

Successfully self-tests three-qubit W state

Self-tests three- and four-qubit GHZ states

Self-tests four-qubit linear cluster state

Abstract

In the usual tomography of multipartite entangled quantum states one assumes that the measurement devices used in the laboratory are under perfect control of the experimenter. In this paper, using the so-called SWAP concept introduced recently, we show how one can remove this assumption in realistic experimental conditions and nevertheless be able to characterize the produced multipartite state based only on observed statistics. Such a black box tomography of quantum states is termed self-testing. As a function of the magnitude of the Bell violation, we are able to self-test emblematic multipartite quantum states such as the three-qubit W state, the three- and four-qubit Greenberger-Horne-Zeilinger states, and the four-qubit linear cluster state.