State preparation of a fluxonium qubit with feedback from a custom FPGA-based platform

Gebauer, R. et al. (2020) State preparation of a fluxonium qubit with feedback from a custom FPGA-based platform. AIP Conference Proceedings, 2241(1), 020015. (doi: 10.1063/5.0011721)

Abstract

We developed a versatile integrated control and readout instrument for experiments with superconducting quantum bits (qubits), based on a field-programmable gate array (FPGA) platform. Using this platform, we perform measurement-based, closed-loop feedback operations with 428 ns platform latency. The feedback capability is instrumental in realizing active reset initialization of the qubit into the ground state in a time much shorter than its energy relaxation time T1. We show experimental results demonstrating reset of a fluxonium qubit with 99.4 % fidelity, using a readout-and-drive pulse sequence approximately 1. 5 µs long. Compared to passive ground state initialization through thermalization, with the time constant given by T1 = 80 µs, the use of the FPGA-based platform allows us to improve both the fidelity and the time of the qubit initialization by an order of magnitude.

• Item Type: Articles
• Additional Information: Funding was provided by the Initiative and Networking Fund of the Helmholtz Association, within the Helmholtz Future Project ‘Scalable solid state quantum computing’ and the Alexander von Humboldt Foundation in the framework of a Sofja Kovalevskaja award endowed by the German Federal Ministry of Education and Research. R. Gebauer acknowledges support by the Helmholtz International Research School for Teratronics (HIRST). N. Karcher acknowledges support by the Karlsruhe School of Elementary Particle and Astroparticle Physics (KSETA). I. Takmakov and A.V. Ustinov acknowledge support from the Ministry of Education and Science of the Russian Federation in the framework of the Increase Competitiveness Program of the National University of Science and Technology MISIS (contract no. K2-2017-081). M. Weides acknowledges support by the European Research Council (ERC) under the Grant Agreement No. 648011, and the Deutsche Forschungsgemeinschaft (DFG) projects INST 121384/138-1FUGG. Facilities use was supported by the KIT Nanostructure Service Laboratory. We acknowledge Qkit [30] for providing a convenient measurement software framework.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Weides, Professor Martin
• Authors: Gebauer, R., Karcher, N., Gusenkova, D., Spiecker, M., Grünhaupt, L., Takmakov, I., Winkel, P., Planat, L., Roch, N., Wernsdorfer, W., Ustinov, A. V., Weber, M., Weides, M., Pop, I. M., and Sander, O.
• College/School: College of Science and Engineering > School of Engineering > Electronics and Nanoscale Engineering
• Journal Name: AIP Conference Proceedings
• Publisher: AIP Publishing
• ISSN: 0094-243X
• ISSN (Online): 1551-7616
• Copyright Holders: Copyright © 2020 The Authors
• First Published: First published in AIP Conference Proceedings 2241(1):020015
• Publisher Policy: Reproduced in accordance with the copyright policy of the publisher