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TT: Fachverband Tiefe Temperaturen

TT 31: Superconducting Electronics: SQUIDs, Qubits, Circuit QED, Quantum Coherence and Quantum Information Systems 1

TT 31.12: Vortrag

Mittwoch, 18. März 2020, 12:30–12:45, HSZ 03

Implementation of a transmon qubit using superconducting granular aluminum — •Patrick Winkel¹, Kiril Borisov², Lukas Grünhaupt¹, Dennis Rieger¹, Martin Spiecker¹, Francesco Valenti^1,3, Alexey V. Ustinov^1,4, Wolfgang Wernsdorfer^1,2,5, and Ioan M. Pop^1,2 — ¹Physikalisches Institut, KIT, Karlsruhe, Germany — ²Institute of Nanotechnology, KIT, Karlsruhe, Germany — ³Institut für Prozessdatenverarbeitung und Elektronik, KIT, Karlsruhe, Germany — ⁴Russian Quantum Center, MISIS, Moscow, Russia — ⁵Institut Néel, CNRS, Grenoble, France

The high kinetic inductance offered by granular aluminum (grAl) has recently been employed for linear inductors in superconducting high-impedance qubits and kinetic inductance detectors. Due to its large critical current density compared to typical Josephson junctions, its resilience to external magnetic fields, and its low dissipation, grAl may also provide a robust source of non-linearity for strongly driven quantum circuits, topological superconductivity, and hybrid systems. Having said that, can the grAl non-linearity be sufficient to build a qubit? Here we show that a small grAl volume shunted by a thin film aluminum capacitor results in a microwave oscillator with an anharmonicity of 4.48 MHz, two orders of magnitude larger than its spectral linewidth, effectively forming a transmon qubit. Resonance fluorescence measurements of the fundamental transition yield an intrinsic qubit linewidth corresponding to a lifetime of 16 μs. This linewidth remains below 150 kHz for in-plane magnetic fields up to 70 mT.