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TT: Fachverband Tiefe Temperaturen

TT 30: Superconductivity - Poster Session

TT 30.58: Poster

Montag, 31. März 2014, 15:00–19:00, P2

Investigation of a tunable transmon qubit in microstrip geometry — •Jochen Braumüller, Lucas Radtke, Oleksandr Lukashenko, Hannes Rotzinger, Martin Weides, and Alexey V. Ustinov — Karlsruhe Institute of Technology (KIT), Physikalisches Institut, 76131 Karlsruhe, Germany

Qubits constitute the main building blocks of a prospective quantum computer. The main challenge is given by their coherence times, determining the feasibility for quantum error correction and scalability. In this work we investigate a transmon qubit having lower sensitivity to charge noise and a reduced dephasing rate compared to a conventional Cooper pair box. The employed microstrip design reduces surface losses due to a decrease in field strength and by focussing of field lines into the substrate. The transmon's large shunt capacitance pads are connected by a split Josephson junction, corresponding to a dc-SQUID. The tunability of the transmon allows frequency selective coupling to other quantum systems. Our design features four frequency detuned microstrip resonators each capacitively coupled to a qubit, enabling frequency multi-plexed simultaneous qubit readout and better statistics of qubit parameters. Chip fabrication is done by sputter deposition of aluminum films and optical lithography. We will present Josephson junction transport characterizations, microwave simulations and qubit measurements.