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/2142/32121
Description
Title
Low-frequency 1/f noise : low temperature measurements and effect on superconducting qubit dephasing
Author(s)
Crane, Trevis Atherton
Issue Date
2005
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
low-frequency noise
critical-current noise power
superconducting qubits
Language
en
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.
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