Roope Uola | LIP6 - Équipe QI

Certifying measurement incompatibility in prepare-and-measure and Bell scenarios

Mon, 03 Mar 2025 00:00:00 +0000

We consider the problem of certifying measurement incompatibility in a prepare-and-measure (PM) scenario. We present different families of sets of qubit measurements which are incompatible, but cannot lead to any quantum over classical advantage in PM scenarios. Our examples are obtained via a general theorem which proves a set of qubit dichotomic measurements can have their incompatibility certified in a PM scenario if and only if their incompatibility can be certified in a bipartite Bell scenario where the parties share a maximally entangled state. Our framework naturally suggests a hierarchy of increasingly stronger notions of incompatibility, in which more power is given to the classical simulation by increasing its dimensionality. For qubits, we give an example of measurements whose incompatibility can be certified against trit simulations, which we show is the strongest possible notion for qubits in this framework.

Roope Uola - Genuinely high-dimensional quantum devices

Thu, 25 Apr 2024 00:00:00 +0000

Genuinely high-dimensional quantum devices

Ce séminaire, donné par Roope Uola, aura lieu le 25 April 2024, à 9:0. Il aura lieu en salle Not specified.

Vous trouverez un plan du campus ici.

Résumé

High-dimensional quantum systems form a rapidly developing research field that covers both theoretical and experimental aspects of quantum communication and, more generally, quantum information theory. These systems provide various advantages over their low-dimensional counterparts in terms of, for example, noise resilience and information carrying capacity. In order to reach such benefits, one needs to possess a system that is not effectively low-dimensional. In this theory talk, I will introduce the concept of genuine high-dimensionality for a range of quantum devices, and discuss how this leads to experimentally testable criteria, that can rule out central low-dimensional simulation protocols in a semi-device independent manner.

Network Quantum Steering

Fri, 22 Oct 2021 00:00:00 +0000

The development of large-scale quantum networks promises to bring a multitude of technological applications as well as shed light on foundational topics, such as quantum nonlocality. It is particularly interesting to consider scenarios where sources within the network are statistically independent, which leads to so-called network nonlocality, even when parties perform fixed measurements. Here we promote certain parties to be trusted and introduce the notion of network steering and network local hidden state (NLHS) models within this paradigm of independent sources. In one direction, we show how results from Bell nonlocality and quantum steering can be used to demonstrate network steering. We further show that it is a genuinely novel effect, by exhibiting unsteerable states that nevertheless demonstrate network steering, based upon entanglement swapping, yielding a form of activation. On the other hand, we provide no-go results for network steering in a large class of scenarios, by explicitly constructing NLHS models.

Device-Independent Quantification of Quantum Resources

Tue, 07 Sep 2021 00:00:00 +0000