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Granular aluminium nanojunction fluxonium qubit

Rieger, D. 1; Günzler, S. ORCID iD icon 1,2; Spiecker, M. 1; Paluch, P. 1,2; Winkel, P. 1,2; Hahn, L. 3; Hohmann, J. K. 3; Bacher, A. 3; Wernsdorfer, W. 1,2; Pop, I. M. 1,2
1 Physikalisches Institut (PHI), Karlsruher Institut für Technologie (KIT)
2 Institut für QuantenMaterialien und Technologien (IQMT), Karlsruher Institut für Technologie (KIT)
3 Institut für Mikrostrukturtechnik (IMT), Karlsruher Institut für Technologie (KIT)

Abstract (englisch):

Mesoscopic Josephson junctions, consisting of overlapping superconducting electrodes separated by a nanometre-thin oxide layer, provide a precious source of nonlinearity for superconducting quantum circuits. Here we show that in a fluxonium qubit, the role of the Josephson junction can also be played by a lithographically defined, self-structured granular aluminium nanojunction: a superconductor–insulator–superconductor Josephson junction obtained in a single-layer, zero-angle evaporation. The measured spectrum of the resulting qubit, which we nickname gralmonium, is indistinguishable from that of a standard fluxonium. Remarkably, the lack of a mesoscopic parallel plate capacitor gives rise to an intrinsically large granular aluminium nanojunction charging energy in the range of tens of gigahertz, comparable to its Josephson energy. We measure coherence times in the microsecond range and we observe spontaneous jumps of the value of the Josephson energy on timescales from milliseconds to days, which offers a powerful diagnostics tool for microscopic defects in superconducting materials.


Postprint §
DOI: 10.5445/IR/1000153980
Veröffentlicht am 10.04.2024
Originalveröffentlichung
DOI: 10.1038/s41563-022-01417-9
Scopus
Zitationen: 6
Dimensions
Zitationen: 9
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Mikrostrukturtechnik (IMT)
Institut für QuantenMaterialien und Technologien (IQMT)
Physikalisches Institut (PHI)
Publikationstyp Zeitschriftenaufsatz
Publikationsmonat/-jahr 12.2022
Sprache Englisch
Identifikator ISSN: 1476-1122, 1476-4660
KITopen-ID: 1000153980
HGF-Programm 47.12.01 (POF IV, LK 01) Advanced Solid-State Qubits and Qubit Systems
Erschienen in Nature Materials
Verlag Nature Research
Band 22
Heft 2
Seiten 194–199
Vorab online veröffentlicht am 08.12.2022
Nachgewiesen in Scopus
Web of Science
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