Thèse soutenue

Transitions de phase quantiques dans le régime de couplage ultrafort de l'electrodynamique quantique
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Auteur / Autrice : Alexandre Baksic
Direction : Cristiano Ciuti
Type : Thèse de doctorat
Discipline(s) : Physique
Date : Soutenance en 2014
Etablissement(s) : Paris 7

Résumé

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Quantum Electrodynamics describes the interaction of light with matter at atomic scale. By placing atoms inside a cavity, it is possible to increase the amplitude of their interaction with vacuum electromagnetic fluctuation. It is even possible to increase it in such a way that a quantum superradiant phase transition occurs, the system passing from a phase called normal (atoms in their ground state and vacuum of photons) to a phase called superradiant (macroscopic number of atomic and photonic excitations in the ground state). However, this theoretical prediction seems prohibited by the "No-go theorem" for superradiant phase transitions. We reconsidered some of the assumptions that led to this theorem and showed that with those new assumptions the superradiant phase transition can occur. We also took advantage of a new field, Circuit Quantum Electrodynamics, which focuses on the behaviour of "artificial" atoms made out of superconducting materials, which are more flexible and controllable than "real" atoms. This greater flexibility, allowed us to consider a new type of superradiant phase transition that led to a richer phase diagram than the traditional one.