Measurements of Decoherence in Three dc SQUID Phase Qubits

Author

Paik, Hanhee ; Cooper, B.K. ; Dutta, S.K. ; Lewis, R.M. ; Ramos, R.C. ; Palomaki, T.A. ; Przybysz, A.J. ; Dragt, A.J. ; Anderson, J.R. ; Lobb, C.J. ; Wellstood, F.C.

Author_Institution

Univ. of Maryland, College Park

Volume

17

Issue

2

fYear

2007

fDate

6/1/2007 12:00:00 AM

Firstpage

120

Lastpage

123

Abstract

We report measurements of spectroscopic linewidth and Rabi oscillations in three thin-film dc SQUID phase qubits. One device had a 6-turn Nb loop, the second had a single-turn Al loop, and the third was a first order gradiometer formed from 6-turn wound and counter-wound Nb coils to provide isolation from spatially uniform flux noise. In the 6-7.2 GHz range, the spectroscopic coherence times for the gradiometer varied from 4 ns to 8 ns, about the same as for the other devices (4 to 10 ns). The time constant for decay of Rabi oscillations was significantly longer in the single-turn Al device (20 to 30 ns) than either of the Nb devices (10 to 15 ns). These results imply that spatially uniform flux noise is not the main source of decoherence or inhomogeneous broadening in these devices.

Keywords

SQUID magnetometers; coherence; oscillations; Rabi oscillations; counter-wound coils; first order gradiometer; inhomogeneous broadening; spatially uniform flux noise; spectroscopic coherence times; spectroscopic linewidth measurements; thin-film dc SQUID phase qubits; Coils; Dielectric losses; Niobium; Phase measurement; Phase noise; Quantum computing; SQUID magnetometers; Spectroscopy; Superconducting device noise; Wounds; Decoherence; Rabi oscillation; flux noise; qubit;

fLanguage

English

Journal_Title

Applied Superconductivity, IEEE Transactions on

Publisher

ieee

ISSN

1051-8223

Type

jour

DOI

10.1109/TASC.2007.898124

Filename

4277654