Self-testing is a procedure for characterizing quantum resources with the minimal level of trust. Up to now it has been used as a device-independent certification tool for particular quantum measurements, channels, and pure entangled states. In this work we introduce the concept of self-testing more general entanglement structures. More precisely, we present the first self-tests of an entangled subspace - the five-qubit code and the toric code. We show that all quantum states maximally violating a suitably chosen Bell inequality must belong to the corresponding code subspace, which remarkably includes also mixed states.
@article{arxiv.2003.02285,
title = {Device-Independent Certification of Genuinely Entangled Subspaces},
author = {Flavio Baccari and Remigiusz Augusiak and Ivan Šupić and Antonio Acín},
journal= {arXiv preprint arXiv:2003.02285},
year = {2021}
}