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TT: Fachverband Tiefe Temperaturen

TT 103: Transport: Poster Session

TT 103.26: Poster

Donnerstag, 19. März 2015, 15:00–18:00, Poster B

Transmon qubits coupled to lumped element LC-readout-resonators — •Joel Cramer¹, Peter Fehlner¹, Jochen Braumüller¹, Steffen Schlör¹, Lucas Radtke¹, Hannes Rotzinger¹, Martin Weides^2,1, and Alexey V. Ustinov^3,1 — ¹Physikalisches Institut, KIT, Wolfgang-Gaede-Straße 1, 76131 Karlsruhe, Germany — ²Institut für Physik, JGU, Staudingerweg 7, 55128 Mainz, Germany — ³Russian Quantum Center, 100 Novaya St., Skolkovo, Moscow, 143025, Russia

Superconducting qubits are among the most promising approaches for unit cells of a quantum computer or simulator. In this work, we investigated capacitively shunted Cooper pair boxes, so-called transmon qubits, each of them coupled to a superconducting readout resonator. Significant detuning of resonator and qubit enables non-demolition readout of the qubit state. Transmon qubits offer simple design and, in principle, large coherence time. In this work quasi-lumped element LC-resonators have been employed,which allow a compact qubit-resonator design of about 400 × 600  µm². In total one chip contains 12 qubit-resonator pairs, each linked to its own fast-flux bias line. To implement and test these circuits, we have chosen simple optical lithography of aluminum films deposited on sapphire substrates. This approach results in relatively large junction sizes and reduced lifetimes due to large number of parasitic two-levels states within the tunnel barrier. Time domain measurements of the fabricated system revealed T1 lifetime of about 0.5  µ s, long enough to explore quantum phenomena like multi-level dressing.