Increasing Spectroscopic Coherence Times of a DC SQUID Phase Qubit by Operating Deeper in the Potential Well
Rupert Lewis, S. K. Dutta, Hanhee Paik, Tauno Palomaki, Benjamin K. Cooper, A. J. Przybysz, Alex J. Dragt, J. R. Anderson, Christopher J. Lobb, F. C. Wellstood · IEEE Transactions on Applied Superconductivity · 2007
We present measurements of the spectroscopic coherence time, T2* of a Nb-AlOx-Nb dc SQUID phase qubit. T2* is calculated from the spectroscopic width of the |0rang to |1rang transition measured at 25 mK. We find that T2*increases at higher transition frequencies corresponding to measurements deeper in the potential well. The measured are consistent with root mean square current noise saturating at 4 nA.