Oxygen vacancies in niobium pentoxide as a source of two-level system losses in superconducting niobium

IF 3.8 2区物理与天体物理 Q2 PHYSICS, APPLIED

Physical Review Applied Pub Date : 2024-08-12 DOI:10.1103/physrevapplied.22.024035

D. Bafia, A. Murthy, A. Grassellino, A. Romanenko

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引用次数: 0

Abstract

We identify a major source of quantum decoherence in three-dimensional superconducting radio-frequency (SRF) resonators and two-dimensional transmon qubits composed of oxidized niobium: oxygen vacancies in the niobium pentoxide, which drive two-level system (TLS) losses. By probing the effect of sequential in situ vacuum-baking treatments on the rf performance of bulk

Nb

SRF resonators and on the oxide structure of a representative

Nb

sample using TOF SIMS, we find a nonmonotonic evolution of cavity quality factor

Q_{0}

, which correlates with the interplay of

{Nb}_{2} O_{5}

vacancy generation and oxide-thickness reduction. We localize this effect to the oxide itself and present the insignificant role of diffused interstitial oxygen in the underlying

Nb

by regrowing the oxide via wet oxidation, which reveals a mitigation of aggravated TLS losses. We hypothesize that such vacancies in the pentoxide serve as magnetic impurities and are a source of TLS-driven rf loss.

Abstract Image

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五氧化二铌中的氧空位是超导铌中两级系统损耗的来源

我们在由氧化铌组成的三维超导射频（SRF）谐振器和二维跨态子量子比特中发现了量子退相干的一个主要来源：五氧化二铌中的氧空位，它驱动了两级系统（TLS）损耗。通过使用 TOF SIMS 探测连续原位真空焙烧处理对块状铌 SRF 谐振器的射频性能和代表性铌样品的氧化物结构的影响，我们发现空腔品质因数 Q0 的非单调演化与 Nb2O5 空位生成和氧化物厚度降低的相互作用有关。我们将这种影响定位到氧化物本身，并通过湿氧化重新生长氧化物来说明扩散的间隙氧在底层铌中的作用微不足道，从而揭示了 TLS 损耗加剧的缓解过程。我们假设五氧化物中的这种空位是磁性杂质，是 TLS 驱动的射频损耗的来源。

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来源期刊

Physical Review Applied PHYSICS, APPLIED-

CiteScore

7.80

自引率

8.70%

发文量

760

审稿时长

2.5 months

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