KIT - Campus North -
Lecture Hall 0-167, Bldg. 640

21.10.2009

Prof. Dr. Alexey Ustinov
Physikalisches Institut
Karlsruhe Institute of Technology, Germany

15:00

Abstract: Josephson plasma oscillations in superconducting tunnel junctions operated as phase qubits show signatures of coherent coupling to microscopic two-level fluctuators (TLFs). TLFs manifest themselves by avoided level crossings in the spectroscopic data reflecting the dependence of the Josephson plasma frequency on the current flowing through the junction. The microscopic TLFs are currently understood as nanoscale dipole states emerging from metastable lattice configurations in amorphous dielectrics forming the tunnel barrier of the Josephson junction or its shunting capacitor. A switching between different metastable charge configurations at low temperatures occurs by quantum tunneling, and such an atomic-scale charge displacement can be associated with the creation of a electrical dipole. Such a dipolar TLF couples to the electrical field inside the junction, which oscillates at the Josephson qubit (plasma) frequency. I will present very recent experiments performed in our newly set up lab in Karlsruhe in which we use a Josephson junction for manipulating quantum states of individual TLFs.