University of Oulu

Hsu, H., Silveri, M., Sevriuk, V., Möttönen, M., & Catelani, G. (2021). Charge dynamics in quantum-circuit refrigeration: Thermalization and microwave gain. In AVS Quantum Science Vol. 3, Issue 4, p. 042001. American Vacuum Society. https://doi.org/10.1116/5.0062868

Charge dynamics in quantum-circuit refrigeration : thermalization and microwave gain

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Author: Hsu, Hao1,2; Silveri, Matti3; Sevriuk, Vasilii4,5;
Organizations: 1JARA Institute for Quantum Information (PGI-11), Forschungszentrum Jülich, 52425 Jülich, Germany
2JARA Institute for Quantum Information, RWTH Aachen University, 52056 Aachen, Germany
3Nano and Molecular Systems Research Unit, University of Oulu, P.O. Box 3000, FI-90014 Oulu, Finland
4QCD Labs, QTF Centre of Excellence, Department of Applied Physics, Aalto University, P.O. Box 13500, FI-00076 Aalto, Finland
5IQM, Keilaranta 19, 02150 Espoo, Finland
6QTF Centre of Excellence, VTT Technical Research Centre of Finland Ltd, P.O. Box 1000, FI-02044 VTT Espoo, Finland
Format: article
Version: published version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe2021101451094
Language: English
Published: AIP Publishing, 2021
Publish Date: 2022-10-08
Description:

Abstract

Previous studies of photon-assisted tunneling through normal-metal–insulator–superconductor junctions have exhibited potential for providing a convenient tool to control the dissipation of quantum-electric circuits in situ. However, the current literature on such a quantum-circuit refrigerator (QCR) does not present a detailed description for the charge dynamics of the tunneling processes or the phase coherence of the open quantum system. Here, we derive a master equation describing both quantum-electric and charge degrees of freedom, and discover that typical experimental parameters of low temperature and yet lower charging energy yield a separation of time scales for the charge and quantum dynamics. Consequently, the minor effect of the different charge states can be taken into account by averaging over the charge distribution. We also consider applying an ac voltage to the tunnel junction, which enables control of the decay rate of a superconducting qubit over four orders of magnitude by changing the drive amplitude; we find an order-of-magnitude drop in the qubit excitation in 40 ns and a residual reset infidelity below 10⁻⁴. Furthermore, for the normal island, we consider the case of charging energy and single-particle level spacing large compared to the superconducting gap, i.e., a quantum dot. Although the decay rates arising from such a dot QCR appear low for use in qubit reset, the device can provide effective negative damping (gain) to the coupled microwave resonator. The Fano factor of such a millikelvin microwave source may be smaller than unity, with the latter value being reached close to the maximum attainable power.

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Series: AVS quantum science
ISSN: 2639-0213
ISSN-E: 2639-0213
ISSN-L: 2639-0213
Volume: 3
Article number: 042001
DOI: 10.1116/5.0062868
OADOI: https://oadoi.org/10.1116/5.0062868
Type of Publication: A1 Journal article – refereed
Field of Science: 114 Physical sciences
Subjects:
Funding: This research was financially supported by the Academy of Finland under Grant Nos. 316619, 319579, 316551, and 335460 and under its Centres of Excellence Programme (Grant Nos. 336810 and 312300), by the Internationalization Fund–Cutting-Edge Ideas initiative of Forschungszentrum Jülich, by the Centre for Quantum Engineering at Aalto under Grant No. JVSG, and by the European Research Council under Grant Nos. 681311 (QUESS) and 680167 (SCAR).
Academy of Finland Grant Number: 316619
Detailed Information: 316619 (Academy of Finland Funding decision)
Dataset Reference: The data that support the findings of this study are available from the corresponding author upon reasonable request.
Copyright information: © 2021 Author(s). Published under an exclusive license by AIP Publishing.