Expérimental
uperconducting quantum circuits, particularly in the circuit Quantum ElectroDynamics (cQED) architecture, have achieved significant progress in recent decades. In this architecture, quantum signals are carried by microwave photons. Most cQED experiments rely on aluminum Josephson Junctions (JJ's), which act as non-linear inductors. This non-linearity enabled the development of crucial non-linear lossless microwave components, such as tunable resonators and low-noise amplifiers, essential for cQED. However, aluminum JJ-based components are limited to low magnetic fields (≲250mT), low temperatures (≲250mK), and frequencies (≲10 GHz), constraining their applications. Using disordered superconductors with a larger superconducting gap, like NbN, could expand these limits by an order of magnitude. This project aims to demonstrate that NbN’s non-linearity can replace Al JJ’s, enabling lossless microwave components for research at higher magnetic fields (~6 T), temperatures (~4 K), and frequencies (~100 GHz). During this master’s project, you’ll work with a team of 30, including 15 Ph.D. researchers, contributing to sample development, design, theory, and nano-fabrication in our cleanroom. You'll also learn cryogenic cooling and perform advanced DC and RF measurements. This project may evolve into a Ph.D. thesis. References: [1] Appl. Phys. Lett. 92, 203501, 2008 [2] Appl. Phys. Lett. 118, 142601, 2021 [3] Appl. Phys. Lett. 118, 054001, 2021