YQI Seminar - Ioan Pop - Karlsruhe Institute of Technology

Event time: 
Wednesday, September 12, 2018 - 11:00am to 12:00pm
YQI Seminar Room - 4th Floor See map
17 Hillhouse Ave
Event description: 

 Granular Aluminum: A High Impedance Material for Coherent Quantum Circuits

Granular Aluminum (grAl) is a self-assembled material obtained by Aluminum deposition in an Oxygen atmosphere. Its properties have been studied extensively since the 60’s, in particular motivated by the measurement of the superconductor-to-insulator transition and the increase of the superconducting gap with increasing granularity. In this talk I will focus on the microwave properties of grAl, in particular its quality factor and its nonlinearity. I will present a circuit quantum electrodynamics (cQED) model to calculate the Kerr coefficients of grAl microwave resonators, starting from their nano-structure, and I will show measurements which support the cQED model. I will argue that the measured quality factor of grAl resonators recommends it as a material of choice for high-impedance quantum circuits, such as the fluxonium, even though quasiparticle poisoning is a limiting factor and should be addressed in future works.