Low -Frequency 1/F Noise: Low Temperature Measurements and Effect on Superconducting Qubit Dephasing

Crane, Trevis Atherton

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https://hdl.handle.net/2142/80518 Copy

Description

Title

Low -Frequency 1/F Noise: Low Temperature Measurements and Effect on Superconducting Qubit Dephasing

Author(s)

Crane, Trevis Atherton

Issue Date

2005

Doctoral Committee Chair(s)

Dale Van Harlingen

Department of Study

Physics

Discipline

Physics

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

Physics, Condensed Matter

Language

eng

Abstract

Low-frequency noise caused by critical-current fluctuations in Josephson junctions can lead to substantial, measurement-induced dephasing in superconducting qubits. The purpose of this work is to measure this noise as a function of temperature and to simulate its effect on the measurement dynamics associated with superconducting qubits. In Nb trilayer junctions we measure the noise power at 1 Hz down to 10 mK and verify a T2 dependence for T > 1 K, below which we observe a flattening of the noise magnitude versus temperature. In Al trilayer junctions we measure the critical-current noise power at 1 Hz from 10 mK to 1.4 K and find no dependence on temperature over this range. Possible reasons for the deviation from a T2 dependence are explored, including heating and sample quality. Simulations of the effect of 1/f noise are performed to examine the consequence of using different qubit sampling methods on expected dephasing times. Using the two sampling methods, we can probe the spectral nature and possible source of the dominant noise in a qubit.

Graduation Semester

2005

Type of Resource

text

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http://hdl.handle.net/2142/80518

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