[Todos] HOY: Coloquios DF - Gerd Schön (KIT), 14hs, Aula Seminario, 2do piso, Pab. I

[Augusto Roncaglia]

COLOQUIOS DEL DEPARTAMENTO DE F�SICA FCEYN - UBA


              En el Aula Seminario, 2do piso, Pab. I,

              Jueves 3/11, 14hs:

              GERD SCHÖN

              Karlsruhe Institute of Technology, Germany



*Properties of individual 2-level defects investigated using
superconducting qubits*
Recent progress with microfabricated quantum devices has revealed that an
ubiquitous source of noise originates from parasitic two-level systems
(TLSs). For superconducting qubits, TLSs residing on surfaces or in tunnel
junctions account for a major part of dephasing and thus pose a roadblock
to the realization of solid-state quantum processors. Recent experiments of
Lisenfeld et al. [1] demonstrated that it is possible to utilize a
superconducting qubit to explore the quantum state evolution of such
high-frequency TLSs. We found that a major source of dephasing of the
probed high-frequency TLSs is their interaction with thermal, low-frequency
TLSs [2]. The so-called standard model of TLS  is sufficient to
quantitatively explain the Ramsey-type experiments. The effect of
low-frequency TLSs is efficiently reduced by spin-echo techniques. The
remaining dephasing observed in the echo protocol is due to further noise
sources with a more white spectrum.

[1] Decoherence spectroscopy with individual two-level tunneling defects.
Lisenfeld, A. Bilmes, S. Matityahu, S. Zanker, M. Marthaler, M. Schechter,
G. Schön, A. Shnirman , G. Weiss and A.V. Ustinov, Sci. Rep.  6, 23786
(2016).

[2] Decoherence of a quantum two-level system by spectral diffusion.
Matityahu, A. Shnirman , G. Schön and M. Schechter, Phys. Rev. B   93,
134208 (2016).
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