Parametric controls for modular quantum computing and quantum devicesLu, Pinlei (2022) Parametric controls for modular quantum computing and quantum devices. Doctoral Dissertation, University of Pittsburgh. (Unpublished) This is the latest version of this item.
AbstractIn superconducting quantum information, qubits are made from low-loss superconducting capacitors, inductors, and transmission lines in combination with nonlinear Josephson elements. In superconducting circuits, the Hamiltonian of the system is very flexible, allowing us to build very nonlinear circuits, like qubits, or very linear circuits, like parametric amplifiers, or anything in between, simply by changing the size of the Josephson junctions we use. The challenge is both to explore which circuits are feasible to realize in the laboratory and embody just the right Hamiltonian to result in a desired quantum behavior. On the other hand, parametric controls, as an approach acts on the Hamiltonian parameter, provides even more potential of realizing different quantum devices for various scenario. This dissertation begins with a discussion of the theory and simulation of quantum superconducting circuits, including circuit quantum electrodynamics and electromagnetic simulation. It next covers the nano-fabrication techniques I used during my PhD. It also contains a review of microwave measurement techniques for quantum circuits. The thesis next details the experimental realization of a simple, two-mode, quantum-limited, Josephson junction based frequency comb, including both the theoretical analysis on the instability of the circuits and the experiments on frequency and time domain. More, we have extended the Hamiltonian engineering techniques to realize a parametrically driven, modular architecture for coupling superconducting qubits. We have realized a ‘tree’ of microwave modes, which can mediate long-range interactions between individual bits by a series of parametric interactions. This architecture, in contrast to the current reliance on the field nearest-neighbor interaction, realizes a far denser of network of interaction between qubits, and thus makes the challenge of achieving large-scale quantum machines less daunting. In the end, my research has shown that devices that are thought of as very different (qubits and amplifiers) can be built and controlled very similarly. In ongoing work detailed in the final sections of this thesis, we have used our growing command of parametric control and Hamiltonian engineering to extend the idea of many-to-many connections among modes via a central SNAIL to realize a 4 transmon 'quantum module'. Share
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