AVS 50th International Symposium
    Magnetic Interfaces and Nanostructures Thursday Sessions
       Session MI-ThA

Paper MI-ThA9
Tunnel Barrier Materials Development for Magnetometer based Josephson Qubits

Thursday, November 6, 2003, 4:40 pm, Room 316

Session: Magnetization Dynamics
Presenter: D.P. Pappas, National Institute of Standards and Technology
Authors: D.P. Pappas, National Institute of Standards and Technology
R. McDermott, National Institute of Standards and Technology
D.A. Hte, National Institute of Standards and Technology
R.W. Simmonds, National Institute of Standards and Technology
K.M. Lang, National Institute of Standards and Technology
J.M. Martinis, National Institute of Standards and Technology
Correspondent: Click to Email
Although Josephson-junction qubits show great promise for quantum computing, the origin of dominant decoherence mechanisms remains unknown. We report Rabi oscillations for a phase qubit, and show that their "coherence amplitude" is significantly degraded by spurious microwave resonances. These resonances appear to arise from changes in the junction critical current, produced by fluctuations in the position of electrons or atoms within the tunnel barrier. We argue this mechanism is a dominant source of decoherence in all present Josephson qubits, and improvements will require materials research directed at the tunnel barriers to remove these spurious resonances. In order to test the influence of the junctions on the cohereance amplitude we have developed tunnel junctions fabricated from both Al/AlO/AL and Al/AlN/Al trilayer structures.