2005/07/26 by John M. Martinis, K. B. Cooper, R. McDermott +8 · 1 citation
Physics and Astronomy · #cond-mat.mtrl-sci
paper · pdf · doi:10.1103/physrevlett.95.210503
shortened version submitted to PRL
arxiv created 2005/07/26 · arxiv updated 2009/12/01
Dielectric loss from two-level states is shown to be a dominant decoherence source in superconducting quantum bits. Depending on the qubit design, dielectric loss from insulating materials or the tunnel junction can lead to short coherence times. We show that a variety of microwave and qubit measurements are well modeled by loss from resonant absorption of two-level defects. Our results demonstrate that this loss can be significantly reduced by using better dielectrics and fabricating junctions of small area \lesssim 10 μ\textrmm2. With a redesigned phase qubit employing low-loss dielectrics, the energy relaxation rate has been improved by a factor of 20, opening up the possibility of multi-qubit gates and algorithms.