Projet de thèse en Physique Théorique
Sous la direction de Serge Florens et de Nicolas Roch.
See in English
Quantum non-linearities of a qubit ultra-strongly coupled to a waveguide
Superconducting systems made from Josephson junctions are versatile quantum- mechanically coherent objects that can be manipulated locally and also coupled to microwave irradiation. Microwave fields can be used as a probe, or even incorporated in a quantum hybrid system made of superconducting and photon degrees of freedom, that can be strongly coupled together. A first chapter of thesis involves devices made of arrays of Josephson junctions that terminate into a Cooper pair quantum dot (charge qubit). This system experiences an alternative form of non-linearity, driven by Coulomb effects, and provides a novel benchmark for studying many-body physics in quantum optics. Linear and non-elastic processes in photon transport will be studied with the ultimate goal of performing Wigner tomography on the coupled superconducting degrees of freedom (qubits) and microwave photons. This theoretical work will be closely related to experimental work at NEEL in the Coherence Quantique group. A second experimental chapter of the thesis will be undertaken between Neel institute and TIFR in India. The goal will be to perform a challenging measurement of correlations in the microwave signal reflected by quantum impurity in order demonstrate the potential of a new generation of parametric amplifiers codeveloped by Neel and TIFR.