Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 103: Transport: Poster Session

TT 103.23: Poster

Thursday, March 19, 2015, 15:00–18:00, Poster B

Decoherence in Two-Level Systems — •Sebastian Zanker¹, Jürgen Lisenfeld², Michael Marthaler¹, Gerd Schön¹, Alexey Ustinov², and Georg Weiß² — ¹Institut für Theoretische Festkörperphysik, Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany — ²Physikalisches Institut, Karlsruhe Institute of Technology , D-76131 Karlsruhe, Germany

We study decoherence of two level systems (TLS) living inside the amorphous AlOx layer of a phase qubit’s Josephson junction. We discuss TLS coupling to phonons, tunneling quasiparticles and other TLS as possible sources of decoherence and compare theoretical decoherence behavior with experimental data. The experiment suggests strong improvements in dephasing times using spin echo protocol as compared to Ramsey dephasing, Γ_Ramsey/Γ_echo∼3−55 which indicates a divergent noise spectral density at low frequencies best matched by either other TLS or quasiparticles.