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HL: Fachverband Halbleiterphysik

HL 55: Superconducting Electronics: SQUIDs, Qubits, Circuit QED, Quantum Coherence and Quantum Information Systems 2 (jointly with MA, HL) (joint session TT/HL)

HL 55.3: Vortrag

Donnerstag, 19. März 2020, 10:00–10:15, HSZ 03

High power dispersive qubit readout and state preparation without parametric amplifier — •Martin Spiecker¹, Daria Gusenkova¹, Richard Gebauer², Lukas Grünhaupt¹, Patrick Winkel¹, Francesco Valenti^1,2, Ivan Takmakov^1,2,3, Dennis Rieger¹, Alexey V. Ustinov^1,4, Wolfgang Wernsdorfer^1,3,5, Oliver Sander², and Ioan M. Pop^{1, 3} — ¹Physikalisches Institut, KIT, Germany — ²Institute for Data Processing and Electronics, KIT, Germany — ³Institute of Nanotechnology, KIT, Germany — ⁴Russian Quantum Center, MISIS, Moscow, Russia — ⁵Institute Neel, CNRS, Grenoble, France

High-fidelity qubit readout is an essential requirement for fault-tolerant quantum algorithms. In theory, within the dispersive readout scheme, the state discrimination can be improved significantly if the resonator’s photon population increases [1]. However, in practice the optimal photon number does usually not exceed 2.5 photons [2], and parametric amplifiers are needed to achieve a substantial signal-to-noise ratio.
In order to investigate the limitations of the readout fidelity we used a fluxonium qubit with a granular aluminum superinductance [3] having the advantage of reduced nonlinearity in comparison to previously used Josephson junction arrays. We demonstrate qubit measurements without a parametric amplifier at readout powers corresponding up to 200 photons in the resonator.

[1] A. Blais et al., PRA 69(6), 062320 (2004)

[2] T. Walter et al., PRA 7.5, 054020 (2017)

[3] L. Grünhaupt and M. Spiecker et al., Nat. Mater. 18, 816-819 (2019)