University of Oulu

Single qubit dephasing in the many-body localization phase transition

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Author: Liimatta, Petri1
Organizations: 1University of Oulu, Faculty of Science, Physics
Format: ebook
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 2.7 MB)
Pages: 50
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Language: English
Published: Oulu : P. Liimatta, 2021
Publish Date: 2021-05-20
Thesis type: Master's thesis
Tutor: Silveri, Matti
Reviewer: Orell, Tuure
Silveri, Matti


We are interested in a model for quantum computer that consists of superconducting qubits, transmons. These transmons are known to experience decoherence which causes unwanted dynamics in their quantum state. In this thesis, one form of decoherence experienced by the transmon, dephasing, is studied. The goal of this research is to differentiate the thermalization phase from the many-body localization phase in a transmon chain by studying dephasing of a single transmon. This phase transition is measured by simulating an array of transmons using the Bose–Hubbard model and calculating the dephasing rate R2 that a single transmon experiences. The many-body localization is shown to have significantly reduced dephasing rates compared to the rates observed at the thermalization phase in three different cases with varying ratio between the interaction strength and the hopping rate U/J = 2, 3.5 and 5. From these results we see that the phase transition is seen when the disorder strength is in the range of W/J = 10−15 on all three cases. An interesting future outlook could be to study the deeper features of the phase transition by examining the the effect of spin-echo pulses on the transmon dephasing.

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Copyright information: © Petri Liimatta, 2021. This publication is copyrighted. You may download, display and print it for your own personal use. Commercial use is prohibited.