SOUAILLE Benjamin : Quantum-to-classical transition seen through quantum signals

Résumé de thèse :

The measurement problem and the quantum-to-classical transition have become central practical problems since the developments in quantum technologies in recent years. The physics of decoherence made it possible to lay the theoretical foundations to understand these problems in depth. A central missing element in this traditional approach is the study of the physics of observers themselves in order to understand wether and how a network of observers can reconstruct a common classic image. This was highlighted by the work of Zurek on quantum Darwinism using tools of quantum information theory, theses ideas are still yet in their infancy and tools are needed to assess the existence of a classical image and the reconstruction abilities of a network of observers. This project aims to build a general resource-based quantum information framework allowing us to precisely analyze the problem of the emergence and reconstruction of a classical description. A specific aim of this work is to put these general ideas to the test via the study measurement signals, bosonic or fermionic. How to define and test the role of resources available to observers in the emergence of a classical consensus remains a largely open question. A simple case study to properly define and test it experimentally is through the study of bosonic signals (multimode light), in the spirit of quantum Darwinism, from circuit electrodynamics and quantum optics experiments. It will help lay the foundations of the “one-shot” quantum information approach to the problem, a necessary step to get closer to experimental reality. Then, the analysis of this problem for fermionic degrees of freedom, especially their entanglement, remains largely to be done. It’s a major issue for fermionic quantum technologies. An important part of the proposed work is to clarify what we mean by fermionic entanglement and to understand how to characterize it through experimental quantum signals, like those of electron quantum optics. Finally, the end goal of the proposed work will be to bridge the gap between the “practical point of view” (measurement signals) and the N-body correlations structure of the quantum state. The central question to address is to determine what kind of correlations are needed between N-bodies for a classical description to exit and being recovered at a certain scale.

Doctorant : SOUAILLE Benjamin

Directeur de thèse : FELLER Alexandre