Superconducting qubit in a resonator : test of the Legget-Garg inequality and single-shot readout
type: Dataset
description: This thesis presents a series of circuit QED (cQED) experiments, in which artificial atoms consisting of superconducting circuits are strongly coupled to the electromagnetic field stored in a microwave resonator. This resonator can be used as a measurement apparatus for the atom, allowing both to address fundamental issues in quantum mechanics, and to develop building blocks for a quantum processor. In a first experiment we continuously monitored the evolution of a quantum system while varying the measurement strength. We observed the crossover from weak to strong measurement regimes, and, ultimately, the freezing of the dynamics by the Quantum Zeno Effect. In the weak measurement regime, we probed if the artificial atom complies with the macroscopic realism hypotheses, from which Leggett and Garg have derived a Bell's inequality in time. The violation of this inequality confirms that although macroscopic, the artificial atom is a truly quantum object. On the quantum information side, we have enriched the proposed cQED quantum processor architecture by demonstrating a high fidelity single-shot qubit readout, a crucial element for quantum processors. This new circuit relies on a dynamical transition of a non-linear resonator. The coupled system formed by the qubit and the non-linear resonator allows in addition to investigate the interplay between strong coupling and non-linear effects --parametric amplification, squeezing...-- opening the new field of non-linear cQED. Finally we have operated a circuit which would potentially be able to mediate operations between two arbitrary qubits: a superconducting resonator which is tunable in frequency.
identifier: NNT: 2010PA066321
issued: 2026-05-11T10:25:51.890187
language: en
modified: 2026-05-11T10:25:51.890192
contact point: Organization
  fn: CCSD
keyword: circuit-quantique
keyword: coherence-quantique
keyword: electrodynamique-quantique
keyword: infoeu-reposemanticsdoctoralthesis
keyword: information-quantique
keyword: jonction-josephson
keyword: josephson-junction
keyword: lecture-dun-bit-quantique
keyword: macroscopic-realism
keyword: measurement-theory
keyword: physqphyphysics-physicsquantum-physics-quant-ph
keyword: quantum-circuit
keyword: quantum-coherence
keyword: quantum-electrodynamics
keyword: quantum-information
keyword: qubit-readout
keyword: realisme-macroscopique
keyword: theorie-de-la-mesure
keyword: theses
landing page: https://theses.hal.science/tel-00815078

Superconducting qubit in a resonator : test of the Legget-Garg inequality and single-shot readout
type: Distribution
format: HTML
issued: 2026-05-11T10:25:52.051050
modified: 2026-05-11T10:25:51.857001
access URL: https://theses.hal.science/tel-00815078

test_moissonnage_selune
type: Agent