Flavien Hirsch - CHSH violation with optimal resources and partial information

Tue, 09 Sep 2025 00:00:00 +0000

CHSH violation with optimal resources and partial information

Ce séminaire, donné par Flavien Hirsch, aura lieu le 09 September 2025, à 13:0. Il aura lieu en salle 26-00/534.

Vous trouverez un plan du campus ici.

Résumé

Entanglement is necessary for Bell nonlocality. In the case of the CHSH inequality/game, Bell pairs i.e. two-qubit maximally entangled states are known to be optimal to reach the Tsirelson bound. Nevertheless, from an informational perspective, one might wonder if Alice and Bob both need to exactly know the state they share to play CHSH optimally, or if some degree of epistemic ignorance is allowed. In this talk, we consider a variation of the standard Bell bipartite scenario, where Alice and Bob play the CHSH with optimal resources i.e. Bell pairs, but imperfect information about them, in order to answer the question How ignorant can Alice and Bob be about the optimal resources they share and still reach the Tsirelson bound, or at least violate the Bell-local bound?

All the best, Marco

Device-independent and semi-device-independent entanglement certification in broadcast Bell scenarios

Sun, 01 Jan 2023 00:00:00 +0000

It has recently been shown that by broadcasting the subsystems of a bipartite quantum state, one can activate Bell nonlocality and significantly improve noise tolerance bounds for device-independent entanglement certification. In this work we strengthen these results and explore new aspects of this phenomenon. First, we prove new results related to the activation of Bell nonlocality. We construct Bell inequalities tailored to the broadcast scenario, and show how broadcasting can lead to even stronger notions of Bell nonlocality activation. In particular, we exploit these ideas to show that bipartite states admitting a local hidden-variable model for general measurements can lead to genuine tripartite nonlocal correlations. We then study device-independent entanglement certification in the broadcast scenario, and show through semidefinite programming techniques that device-independent entanglement certification is possible for the two-qubit Werner state in essentially the entire range of entanglement. Finally, we extend the concept of EPR steering to the broadcast scenario, and present novel examples of activation of the two-qubit isotropic state. Our results pave the way for broadcast-based device-independent and semi-device-independent protocols.

Flavien Hirsch | LIP6 - Équipe QI

Flavien Hirsch - CHSH violation with optimal resources and partial information

CHSH violation with optimal resources and partial information

Résumé

Device-independent and semi-device-independent entanglement certification in broadcast Bell scenarios