Un, S; de Graaf, S; Bertet, P; Kubatkin, S; Danilov, A (2022) On the nature of decoherence in quantum circuits: Revealing the structural motif of the surface radicals in α-Al2O3. Science Advances, 8 (14). eabm6169

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Abstract

Quantum computing puts new stringent demands on the quality of materials and interfaces in the effort to increase device coherence. Paramagnetic impurities, thought to be mainly adsorbed species, produce both flux and charge noise in devices, which leads to the decoherence of fragile quantum states. To date, very little is known about the chemical origin of these centers. Here we perform high frequency electron paramagnetic resonance (HFEPR) measurements of α-Al2O3 – a material commonly used for quantum devices as a substrate, and unavoidably present in amorphous form in superconducting Al circuits and qubits. We show that radical centers on α-Al2O3 are, contrary to previous understandings, spin delocalized structures at the surface created by reaction with molecular oxygen. This chemistry is common to many metal oxides and may in part explain the ubiquity of noise and decoherence in quantum devices. As such, HFEPR can be used to inform decoherence mitigation strategies.

Item Type:	Article
Keywords:	High-field electron paramagnetic resonance EPR ESR surface spins decoherence quantum circuits
Subjects:	Nanoscience > Surface and Nanoanalysis
Divisions:	Quantum Technologies
Identification number/DOI:	10.1126/sciadv.abm6169
Last Modified:	24 May 2022 12:44
URI:	http://eprintspublications.npl.co.uk/id/eprint/9451

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