Regensburg 2016 – wissenschaftliches Programm

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MA: Fachverband Magnetismus

MA 6: Transport: Quantum Coherence and Quantum Information Systems - Experiment
(Joint session of HL, MA and TT organized by TT)

MA 6.7: Hauptvortrag

Montag, 7. März 2016, 11:30–12:00, H22

Coherent Suppression of Quasiparticle Dissipation in a Superconducting Artificial Atom — •Ioan Pop — Physikalisches Institut, Karlsruhe Institute of Technology, 76131 Karlsruhe, Germany — Department of Applied Physics, Yale University, New Haven, CT 06520, USA

We demonstrate immunity to quasiparticle dissipation in a Josephson junction. At the foundation of this protection rests a prediction by Brian Josephson from fifty years ago: the particle-hole interference of superconducting quasiparticles when tunneling across a Josephson junction [1]. The junction under study is the central element of a fluxonium artificial atom, which we place in an extremely low loss environment and measure using radio-frequency dispersive techniques [2]. Furthermore, by using a quantum limited amplifier (a Josephson Parametric Converter) we can observe quantum jumps between the 0 and 1 states of the qubit in thermal equilibrium with the environment. The distribution of the times in-between the quantum jumps reveals quantitative information about the population and dynamics of quasiparticles[3]. The data is entirely consistent with the hypothesis that our system is sensitive to single quasiparticle excitations, which opens new perspectives for quasiparticle monitoring in low temperature devices.

[1] B. D. Josephson, Physics Letters 1, 251 (1962)

[2] I. M. Pop et al., Nature 508 (2014)

[3] U. Vool et al., PRL 113 (2014)