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Full-Text Articles in Physical Sciences and Mathematics
Vortices And Quasiparticles In Superconducting Microwave Resonators, Ibrahim Nsanzineza
Vortices And Quasiparticles In Superconducting Microwave Resonators, Ibrahim Nsanzineza
Dissertations - ALL
Superconducting resonators with high quality factors are of great interest in many areas. However, the quality factor of the resonator can be weakened by many dissipation channels including trapped magnetic flux vortices and nonequilibrium quasiparticles which can significantly impact the performance of superconducting microwave resonant circuits and qubits at millikelvin temperatures. Quasiparticles result in excess loss, reducing resonator quality factors and qubit lifetimes. Vortices trapped near regions of large microwave currents also contribute excess loss. However, vortices located in current-free areas in the resonator or in the ground plane of a device can actually trap quasiparticles and lead to a …
Flux-Tunable Superconducting Transmons For Quantum Information Processing, Matthew Ware
Flux-Tunable Superconducting Transmons For Quantum Information Processing, Matthew Ware
Dissertations - ALL
In this thesis, I describe a series of experiments using flux-tunable transmon qubits for quantum information processing. These qubits are designed with different levels of Josephson junction asymmetry. The first two chapters of this thesis will introduce the reader to superconducting qubits and circuit quantum electrodynamics. I will present experiments using the cQED architecture to implement fast photon swapping between an asymmetric qubit and a superconducting resonator using flux-driven sidebands. This is the first experimental observation of flux-driven sidebands in a superconducting system. This process also allows photon swaps between qubit and resonator to first order in the qubit-resonator coupling …
Microstrip Superconducting Quantum Interference Devices For Quantum Information Science, Michael Paul Defeo
Microstrip Superconducting Quantum Interference Devices For Quantum Information Science, Michael Paul Defeo
Physics - Dissertations
Quantum-limited amplification in the microwave frequency range is of both practical and fundamental importance. The weak signals corresponding to single microwave photons require substantial amplification to resolve. When probing quantum excitations of the electromagnetic field, the substantial noise produced by standard amplifiers dominates the signal, therefore, several averages must be accumulated to achieve even a modest signal-to-noise ratio. Even worse, the back-action on the system due to amplifier noise can hasten the decay of the quantum state. In recent years, low-noise microwave-frequency amplification has been advancing rapidly and one field that would benefit greatly from this is circuit quantum electrodynamics …