Decoherence in Josephson qubits from dielectric Loss

John M. Martinis, K. B. Cooper, R. McDermott, Matthias Steffen, Markus Ansmann, K. D. Osborn, K. Cicak, Seongshik Oh, D. P. Pappas, R. W. Simmonds, Clare C. Yu

Research output: Contribution to journalArticlepeer-review

312 Scopus citations


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 10μm2. 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 multiqubit gates and algorithms.

Original languageEnglish (US)
Article number210503
JournalPhysical review letters
Issue number21
StatePublished - Nov 18 2005

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)


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