Shape & cutoff in superconducting qubits, work fluctuations in correlation creation, & critical commentary

quantum field theory;superconducting qubits;unruh-dewitt detectors;critiques of physics

McKay, Emmaadvisor:Martin-Martinez, Eduardo ; affiliation1:Faculty of Mathematics ; Martin-Martinez, Eduardo ;

University of Waterloo

关键词: superconducting qubits;    Master Thesis;    quantum field theory;    critiques of physics;    unruh-dewitt detectors;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/14373/3/McKay_Emma.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

Part IWe apply the Unruh-DeWitt model for a qubit interacting with a quantum field to asuperconducting qubit. We use the flexibility of this model, as compared to the spin-bosonmodel used widely in the literature, to investigate the effect of an ultraviolet cutoff in thefield and the finite size of a qubit on the dynamics of a qubit. In studying these features inthe setup of a qubit coupled to an infinite transmission line, we find that both the shapeand scale of the ultraviolet cutoff have a significant effect on the qubit’s dynamics. Forexperimentally reasonable parameters, we estimate that using an inaccurate model for theultraviolet cutoff present in the line could introduce errors in calculation of probability ofspontaneous emission of the qubit of around 10%. This is particularly interesting in light ofthe fact that superconducting lines have natural ultraviolet cutoffs due to the breakdownof superconductivity for high frequency electromagnetic waves.Part IIWe investigate a unitary protocol to create correlations in a bipartite quantum me-chanical system. The protocol was initially motivated by its optimal average work cost.We calculate the fluctuations in the work cost and show that for maximal generation ofcorrelations, the fluctuations in the work cost are of the order of the average work cost,making the protocol energetically rather unreliable. We additionally explore some of thenuances of the discussion around work in quantum systems with discussion of the currentliterature as well as some philosophical motivations of the most widely used definitions ofwork.Throughout the thesis, we comment on the motivations for this research and its effecton our world. In doing so, we find multiple ways that supporting the project of developingquantum technology supports injustice. We also model a methodology for engaging withsocietal and ethical implications of work in theoretical physics.