Séminaire/Seminar – Dispersive coupling of resonators for qubit readout – Alexis Jouan – 7/04/23

11 h 00 min-12 h 00 min
INSP - Sorbonne Université
Sorbonne Université Campus Pierre et Marie Curie 4 place Jussieu, Paris, 75005
Type d’évènement/Event category

Barre 12-22, 4e étage, pièce 426

Alexis Jouan, LPEM – ESPCI


Light can be used to determine the state of a quantum system, by measuring the frequency of a cavity in interaction with this system. This presentation will be focused on the readout of two different qubits using high frequency resonators. The first one, is the spin qubit in Silicon [1]. During my first postdoc at UNSW in the group of Andrew Dzurak, we developed an innovative readout method based on the capacitive coupling of a resonator with a double quantum dot in Silicon [2]. Due to Pauli spin blockade, the quantum capacitance of the double dot contribution depends on the symmetry of the electron pair spin (singlet or triplet). This method, called dispersive gate sensing, is now widely used in the community and reaches very high readout fidelities [3]. The second type of qubit I will present is the Fluxonium qubit [4], that I fabricated and characterised at ENS Lyon in the group of Benjamin Huard. One naturally want to increase the number of photons in the cavity to determine more accurately the state of the qubit, but it was shown that this increase quickly brings the qubit out of the computational subspace [5]. I will present the effect of a strong measurement on the dynamics of a Fluxonium qubit.