Composable framework for device-independent state certification

TL;DR

This paper introduces a new framework for certifying quantum states in a device-independent, composable manner, allowing integration into larger quantum protocols without trusting internal device details.

Contribution

It develops a composable, device-independent state certification method based on the extractability measure, applicable to sequences of independent states, and demonstrates it with the CHSH inequality.

Findings

Certifies the singlet state in a DI, composable way using CHSH.

Introduces methods to compute extractability under local operations.

Shows the framework's applicability to non-identical state sequences.

Abstract

Certifying a quantum state in a device-independent (DI) manner, in which no trust is placed on the internal workings of any physical components, is a fundamental task bearing various applications in quantum information theory. The composability of a state certification protocol is key to its integration as a subroutine within information-theoretic protocols. In this work, we present a composable certification of quantum states in a DI manner under the assumption that a source prepares a finite sequence of independent quantum states that are not necessarily identical. We show that the security relies on the DI analog of the fidelity, called the extractability. We develop methods to compute this quantity under local operations and classical communication in certain Bell scenarios that self-test the singlet state, which may also be of independent interest. Finally, we demonstrate our framework by certifying the singlet state in a composable and DI manner using the Clauser-Horne-Shimony-Holt inequality.