Berlin 2008 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 22: Transport: Poster Session

TT 22.19: Poster

Mittwoch, 27. Februar 2008, 14:00–18:00, Poster B

Superconducting Quantum Circuits: Building Blocks for cQED experiments — •Thomas Niemczyk, Elisabeth Hoffman, Achim Marx, and Rudolf Gross — Walther-Meissner-Institut, Bayerische Akademie der Wissenschaftem, Garching

There have been numerous promising advancements in the field of quantum information processing (QIP) since its conception. Coupling superconducting (SC) qubits to high-Q SC resonators opens the fascinating field of circuit quantum electrodynamics (cQED). Recent experiments with SC charge qubits have demonstrated the fundamental interaction of these ’artificial atoms’ with a single microwave photon. In our work we are concentrating on the development of SC flux-qubits and the required building blocks for cQED. We present designs and realizations of different SC coplanar waveguide resonators for cQED experiments with quality factors up to 2.3 · 10⁵. Furthermore, we present measurements on high-transparency Al/AlO_x/Al Josephson-Junctions (JJ). The JJs were characterized at 500 mK and exhibit E_J/E_C ratios of 30 - 70 with critical current densities J_c larger than 1000 A/cm². Finally, we present measurements on different realizations of microstrip hybrid rings, which act as a beam splitter in the microwave regime. The hybrid rings were characterized at 4.2 K and 1.5 K and exhibit isolation (S₃₁) and coupling (S₂₃) spectra suitable for a quantum homodyne measurement scheme for the detection of single microwave photons.
Financial support by the DFG via SFB 631 and the Excellence Initiative via NIM is gratefully acknowledged.