Decoupling a Cooper-Pair Box to Enhance the Lifetime to 0.2 ms

作者：Kim Z^*; Suri B; Zaretskey V; Novikov S; O**orn K D; Mizel A; Wellstood F C; Palmer B S

来源：Physical Review Letters, 2011, 106(12): 120501.

DOI：10.1103/PhysRevLett.106.120501

We present results on a circuit QED experiment in which a separate transmission line is used to address a quasilumped element superconducting microwave resonator which is in turn coupled to an Al/AlO(x)/Al Cooper-pair box charge qubit. With our device, we find a strong correlation between the lifetime of the qubit and the inverse of the coupling between the qubit and the transmission line. At the smallest coupling we measured, the lifetime of the Cooper-pair box was T(1) = 200 mu s, which represents more than a twentyfold improvement in the lifetime of the Cooper-pair box compared with previous results. These results imply that the loss tangent in the AlO(x) junction barrier must be less than about 4 X 10(-8) at 4.5 GHz, about 4 orders of magnitude less than reported in larger area Al/AlO(x)/Al tunnel junctions.

• 出版日期2011-3-22