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TT: Fachverband Tiefe Temperaturen

TT 21: Superconductivity: Poster Session

TT 21.45: Poster

Montag, 16. März 2015, 15:00–18:00, Poster B

Temperature dependence of coherence in transmon qubits — •Steffen Schlör¹, Jochen Braumüller¹, Oleksandr Lukashenko¹, Hannes Rotzinger¹, Martin Sandberg², Michael R. Vissers², David P. Pappas², Martin Weides¹, and Alexey V. Ustinov¹ — ¹Physikalisches Institut, KIT, 76131 Karlsruhe, Germany — ²NIST, Boulder, CO 80305, United States

Superconducting qubits are a promising field of research, not only with respect to quantum computing but also as highly sensitive detectors and due to the possibility of using them to study fundamental implications of quantum mechanics. The requirements for qubits that can be used as building blocks in a potential quantum computer are challenging. Modern superconducting qubits like the transmon are strong candidates for achieving these goals. The main challenge here is to increase the coherence of prepared quantum states. Here, we experimentally investigate the influence of temperature variation on relaxation and dephasing of a transmon qubit. Our goal is to understand decoherence mechanisms in material optimized circuits. Aiming at longer coherence, in this case peaking over 50 µs for T₁ and T₂, our samples are fabricated at NIST using two different materials. Low-loss TiN was used for the shunt capacitance as well as the resonator, combined with shadow evaporated ultra-small Al-AlO_x-Al Josephson junctions. We will present temperature-dependent data on qubit relaxation and dephasing times as well as power spectra. Our data will be compared to previously obtained temperature dependent data for other types of qubits.