Low-frequency 1/f noise : low temperature measurements and effect on superconducting qubit dephasing

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date

2012

Author dc:creator

• Crane, Trevis Atherton

• low-frequency noise
• critical-current noise power
• superconducting qubits

Statement dc:rights

• ©2005 Crane

Language dc:language

en

Identifier

Q. 537.623 Tc5c
FILM 2005 C85

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/32121