Activation of post-quantum steering

TL;DR

This paper demonstrates how to activate post-quantum EPR steering in a network, enabling the observation of post-quantum correlations in Bell tests, and introduces methods for self-testing bipartite quantum assemblages with post-quantum resources.

Contribution

It introduces a method to activate post-quantum steering in networks, linking it to observable post-quantum correlations and self-testing techniques.

Findings

Post-quantum steering can be activated in larger networks.

Networks can violate Tsirelson bounds without showing post-quantum non-locality.

Self-testing of bipartite assemblages with post-quantum resources is possible.

Abstract

There are possible physical theories that give greater violations of Bell's inequalities than the corresponding Tsirelson bound, termed post-quantum non-locality. Such theories do not violate special relativity, but could give an advantage in certain information processing tasks. There is another way in which entangled quantum states exhibit non-classical phenomena, with one notable example being Einstein-Podolsky-Rosen (EPR) steering; a violation of a bipartite Bell inequality implies EPR steering, but the converse is not necessarily true. The study of post-quantum EPR steering is more intricate, but it has been shown that it does not always imply post-quantum non-locality in a conventional Bell test. In this work we show how to distribute resources in a larger network that individually do not demonstrate post-quantum non-locality but violate a Tsirelson bound for the network. That is, we show how to activate post-quantum steering so that it can now be witnessed as post-quantum correlations in a Bell scenario. One element of our work that may be of independent interest is we show how to self-test a bipartite quantum assemblage in a network, even assuming post-quantum resources.