Pure dephasing in flux qubits due to flux noise with spectral density scaling as 1/fα

Anton, S. M., Mueller, C., Birenbaum, J. S., O'Kelley, S. R., Fefferman, A. D., Golubev, D. S., Hilton, G. C., Cho, H. -M., Irwin, K. D., Wellstood, F. C., Schoen, Gerd, Shnirman, A. and Clarke, John (2012) Pure dephasing in flux qubits due to flux noise with spectral density scaling as 1/fα. Physical Review B - Condensed Matter and Materials Physics, 85 22: 1-6. doi:10.1103/PhysRevB.85.224505

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Author Anton, S. M.
Mueller, C.
Birenbaum, J. S.
O'Kelley, S. R.
Fefferman, A. D.
Golubev, D. S.
Hilton, G. C.
Cho, H. -M.
Irwin, K. D.
Wellstood, F. C.
Schoen, Gerd
Shnirman, A.
Clarke, John
Title Pure dephasing in flux qubits due to flux noise with spectral density scaling as 1/fα
Formatted title
Pure dephasing in flux qubits due to flux noise with spectral density scaling as 1/fα
Journal name Physical Review B - Condensed Matter and Materials Physics   Check publisher's open access policy
ISSN 1098-0121
1550-235X
Publication date 2012-06-05
Sub-type Article (original research)
DOI 10.1103/PhysRevB.85.224505
Open Access Status File (Publisher version)
Volume 85
Issue 22
Start page 1
End page 6
Total pages 6
Place of publication College Park, MD, United States
Publisher American Physical Society
Language eng
Formatted abstract
For many types of superconducting qubits, magnetic flux noise is a source of pure dephasing. Measurements on a representative dc superconducting quantum interference device (SQUID) over a range of temperatures show that S Φ(f)=A2/ (f /1Hz )α, where S Φ is the flux noise spectral density, A is of the order of 1 μΦ 0Hz -1 /2, 0.61≤α≤0.95, and Φ 0 is the flux quantum. For a qubit with an energy level splitting linearly coupled to the applied flux, calculations of the dependence of the pure dephasing time τ φ of Ramsey and echo pulse sequences on α for fixed A show that τ φ decreases rapidly as α is reduced. We find that τ φ is relatively insensitive to the noise bandwidth, f 1≤f≤f 2, for all α provided the ultraviolet cutoff frequency f 21/ τ φ. We calculate the ratio τ φ,E/ τ φ,R of the echo (E) and Ramsey (R) sequences and the dependence of the decay function on α and f 2. We investigate the case in which S Φ(f 0) is fixed at the "pivot frequency" f 0≠1 Hz while α is varied and find that the choice of f 0 can greatly influence the sensitivity of τ φ,E and τ φ,R to the value of α. Finally, we present calculated values of τ φ in a qubit corresponding to the values of A and α measured in our SQUID.
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status Non-UQ
Additional Notes Article # 224505

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Mathematics and Physics
 
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