A Purity Benchmarking Study of Superconducting Single-qubit Fluctuations
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Date
2023-07-31
Authors
Zhu, Auda
Advisor
Mariantoni, Matteo
Journal Title
Journal ISSN
Volume Title
Publisher
University of Waterloo
Abstract
Quantum processes are susceptible to errors. Over the years, numerous noise models,
such as two-level system noise and flux noise, have been proposed by physicists to describe
the mechanisms behind the error sources affecting quantum processes. However, a compre-
hensive understanding of the quantum noise landscape, particularly on longer timescales,
is still under active exploration. This thesis contributes to this ongoing effort, exploring
long-term quantum noise through the lens of a superconducting Xmon transmon qubit.
In our study, we explore the long-term qubit noises by conducting continuous purity
benchmarking experiments, utilizing a set of established metrics to gauge the quantum
errors. These metrics, namely the average gate fidelity and unitarity, provides a more
detailed characterization of quantum error compared to the commonly studied variables
such as T1 and frequency detuning, including characterization of the coherence property.
These metrics are also the subject of intense discussions, particularly in the fields of quan-
tum algorithms and quantum information processing hardware development. We measured
the coherent and incoherent quantum error for very long time periods, up to 440 hours.
Through these experiments. we gain valuable insights into the nature of the quantum noise
and its impact on qubit coherence.
Following the experiments, we further attempt to reconcile our observations with well-
established models, namely the two-level system and flux noise, through simultaneous
measurements and comprehensive simulations. While we succeed in explaining certain
aspects of the experimental results, our findings also highlight intriguing discrepancies
between experimental observations and simulations, thus prompting further research.
Description
Keywords
purity benchmarking, randomized benchmarking, qubit noise, coherence, long-period