Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 6: Superconductivity: Tunnelling & Josephson Junctions

TT 6.2: Talk

Monday, March 11, 2013, 09:45–10:00, H18

Direct observation and characterization of two coherent and strongly coupled TLS using a superconducting phase qubit — •Grigorij J. Grabovskij¹, Jürgen Lisenfeld¹, Jared H. Cole², Clemens Müller³, Georg Weiss¹, and Alexey V. Ustinov¹ — ¹Karlsruhe Institute of Technology, Physikalisches Institut, 76131 Karlsruhe, Germany — ²Chemical and Quantum Physics, School of Applied Sciences, RMIT University, Melbourne, 3001, Australia — ³Département de Physique, Université de Sherbrooke, Sherbrooke, Québec, Canada J1K 2R1

Atomic two-level tunneling systems (TLS) are known to be present in amorphous dielectrics. The use of a superconducting phase qubit allows one to study the quantum mechanical properties of individual and coherent TLS in detail. Recently, we demonstrated that controlled flexing of the substrate with a piezo actuator changes the TLS resonance frequency. Some TLS show a hyperbolic frequency dependence [1]. In further measurements, we found and investigated in detail two interacting TLS. The spectroscopically observed frequency-strain dependence exhibits a characteristic S-like shape with clearly visible avoided level crossings, both being clear signatures of the coherently coupled TLS. By measuring and analyzing this 4-level system we determine energies of the states, coupling constants and coherence times. From these data, we estimate the spatial separation between these two interacting TLS.
[1] G. J. Grabovskij et al., Science 338, 232 (2012)