Probing two-level systems with electron spin inversion recovery of defects at the 
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 interface

Belli, M.; Fanciulli, M.; Sousa, Rogério de

doi:10.1103/physrevresearch.2.033507

Cited by 5 publications

(2 citation statements)

References 25 publications

(43 reference statements)

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“…However, it is needless to say that a detected unpaired electron present in a device could also constitute a charge dipole. Thus, EPR also has direct relevance for understanding TLS either directly or via spins that are influenced by TLS in their vicinity [82, [85][86][87], linking the associated spin to a chemical entity or environment.…”

Section: Chemical Identification By Magnetic Resonancementioning

confidence: 99%

Chemical and structural identification of material defects in superconducting quantum circuits

Graaf

Un²,

Shard³

et al. 2022

Mater. Quantum. Technol.

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Quantum circuits show unprecedented sensitivity to external fluctuations compared to their classical counterparts, and it can take as little as a single atomic defect somewhere in a mm-sized area to completely spoil device performance. For improved device coherence it is thus essential to find ways to reduce the number of defects, thereby lowering the hardware threshold for achieving fault-tolerant large-scale error-corrected quantum computing. Given the evasive nature of these defects, the materials science required to understand them is at present in uncharted territories, and new techniques must be developed to bridge existing capabilities from materials science with the needs identified by the superconducting quantum circuit community. In this paper, we give an overview of methods for characterising the chemical and structural properties of defects in materials relevant for superconducting quantum circuits. We cover recent developments from in-operation techniques, where quantum circuits are used as probes of the defects themselves, to in situ analysis techniques and well-established ex situ materials analysis techniques. The latter is now increasingly explored by the quantum circuits community to correlate specific material properties with qubit performance. We highlight specific techniques which, given further development, look especially promising and will contribute towards a future toolbox of material analysis techniques for quantum.

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Section: Chemical Identification By Magnetic Resonancementioning

confidence: 99%

Chemical and structural identification of material defects in superconducting quantum circuits

Graaf

Un²,

Shard³

et al. 2022

Mater. Quantum. Technol.

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show abstract

“…There are two known types of TLSs [17]: "Atomic TLSs" occur when impurities tunnel between pairs of equivalent sites. A notable example is Nb:O,H [18], where interstitial O creates a bistable trap for H. Only two locations for H are stable for a given interstitial O, leading to octahedral averaging of p, with sharply defined p. The other type is the "glassy TLS" realized by bistable configurations involving several atoms in an amorphous lattice [19,20]. The wide variation in glassy TLS morphology indicates a broad distribution for p, with implications for dielectric loss.…”

Section: Introductionmentioning

confidence: 99%

Modelling dielectric loss in superconducting resonators: Evidence for interacting atomic two-level systems at the Nb/oxide interface

Gorgichuk¹,

Junginger²,

Sousa³

2022

Preprint

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While several experiments claim that two-level system (TLS) defects in amorphous oxides are responsible for energy relaxation in superconducting resonators and qubits, only a few are able to provide quantitative explanation of their data in terms of the conventional noninteracting TLS model. Here several models of dielectric loss are considered to explain available experimental data of photon loss in TESLA cavities. These cavities contain a single amorphous niobium/niobium oxide interface in their interior, making them convenient testbeds for analysis of TLS parameters. It is shown that the noninteracting model does indeed yield the best fit to experimental data, provided that a one-species model with sharp modulus of electric dipole moment p is assumed for electropolished cavities with a thin (5 nm) amorphous oxide. In contrast, a two-species model with two different p's is required to explain data in anodized cavities with a thick 100 nm oxide layer. The small variation in TLS microscopic structure is indicative of "atomic TLSs" such as Nb:O,H, realized by an atom (H) trapped in one of two locations near an O interstitial.

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Model for 1/f flux noise in superconducting aluminum devices: Impact of external magnetic fields

Aquino

Sousa

2023

Applied Physics Letters

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Superconducting quantum interference devices and related circuits made of aluminum are known to display 1/ω flux noise, where ω is frequency. A recent experiment showed that the application of an external magnetic field in the 10–100 G range changed the noise to a single Lorentzian peaked at ω = 0. Here, it is shown that a model based on independent impurity spin flips with coexisting cross and direct mechanisms of spin relaxation may explain these experiments. The model shows that application of an external magnetic field can be used to reduce the impact of flux noise in qubits.

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Probing two-level systems with electron spin inversion recovery of defects at the Si/SiO2 interface

Cited by 5 publications

References 25 publications

Chemical and structural identification of material defects in superconducting quantum circuits

Chemical and structural identification of material defects in superconducting quantum circuits

Modelling dielectric loss in superconducting resonators: Evidence for interacting atomic two-level systems at the Nb/oxide interface

Model for 1/f flux noise in superconducting aluminum devices: Impact of external magnetic fields

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