Materials in superconducting quantum circuits

Xiong, Kanglin; Feng, Jiagui; Zheng, Yingkui; Cui, Jiangyu; Yung, Man‐Hong; Zhang, Shengyu; Li, Shunfeng; Yang, Hui

doi:10.1360/tb-2021-0479

Cited by 11 publications

(10 citation statements)

References 53 publications

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“…It is believed that most lossy channels emerged in the material growth and device fabrication 10,11 . Speci cally, the dielectric loss arises from three interfaces 12 , i.e., the amorphous oxide layer at the superconductor-air (MA) interface, the amorphous oxide layer at the substrate-air (SA) interface, and the amorphous layer at the superconductor-substrate (MS) interface. Substrate cleaning, epitaxial lm growth, and subsequently etching method for the qubit fabrication can improve the MS interface [13][14][15][16][17] .…”

Section: Introductionmentioning

confidence: 99%

A stable and low loss oxide layer on α-Ta (110) film for superconducting qubits

Ding,

zhou,

Wang

et al. 2023

Preprint

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The dielectric loss of amorphous oxide layers is a major limiting factor for the coherent time of superconducting qubits. Usually, the surface oxides of superconductor film are lossy and unstable in air. To increase the coherence time, it is essential for qubits to have stable and low dielectric loss oxides, either as barrier or passivation layers. Here, we demonstrate that a kind of amorphous tantalum oxide on α-Ta (110) film is robust and stable by means of chemical and structural analysis. Such kind of oxide layer forms in a self-limiting process on the surface of α-Ta (110) film in piranha solution, yielding stable thickness and steady chemical composition. Quarter-wavelength coplanar waveguide resonators are made to study the loss of this oxide. One fresh resonator have a Qi of 3.0×106 in the single photon region. The Qi of most devices are higher than 2.0×106. And most of them are still over one million even after exposed to air for months. Based on these findings, we propose an all-tantalum superconducting qubit utilizing such oxide as passivation layers, which possess low dielectric loss and improved stability.

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Section: Introductionmentioning

confidence: 99%

A stable and low loss oxide layer on α-Ta (110) film for superconducting qubits

Ding,

zhou,

Wang

et al. 2023

Preprint

Self Cite

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“…However, it is not only di cult to achieve uniform junction patterns using low-energy electron beam exposure (due to charging effect), but also hard to improve uniform junction resistance using laser annealing (due to transparency to light). Therefore, exploring the fabrication process for Al/AlO x /Al junctions with high uniformity on a large scale on sapphire is critical for developing high-quality superconducting quantum processors 13,14 .…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Al/AlOx/Al junctions with high uniformity and stability on sapphire substrates

Zheng

Li²,

Ding³

et al. 2023

Preprint

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Tantalum and aluminum on sapphire are widely used platforms for qubits of long coherent time. As quantum chips scale up, the number of Josephson junctions on Sapphire increases. Thus, both the uniformity and stability of the junctions are crucial to quantum devices, such as scalable superconducting quantum computer circuit, and quantum-limited amplifiers. By optimizing the fabrication process, especially, the conductive layer during the electron beam lithography process, Al/AlOx/Al junctions of sizes ranging from 0.0169 to 0.04 µm2 on sapphire substrates were prepared. The relative standard deviation of room temperature resistances (RN) of these junctions is better than 1.7% on 15 mm×15 mm chips, and better than 2.66% on 2 inch wafers, which is the highest uniformity on sapphire substrates has been reported. The junctions are robust and stable in resistances as temperature changes. The resistances increase by the ratio of 9.73% relative to RN as the temperature ramp down to 4K, and restore their initial values in the reverse process as the temperature ramps back to RT. After being stored in a nitrogen cabinet for 100 days, the resistance of the junctions changed by1.16% in average. The demonstration of uniform and stable Josephson junctions in large area paves the way for the fabrication of superconducting chip of hundreds of qubits on sapphire substrates.

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“…[5][6][7][8][9] On the other hand, eliminating decoherence channels such as two-level defects, which are closely related to the materials and device fabrication processes, paves the way for future steps. [10][11][12][13][14][15] To that purpose, novel materials [16][17][18][19][20] and innovative manufacturing technologies [21][22][23][24] are explored to improve the coherence times of superconducting qubits.…”

mentioning

confidence: 99%

“…The atomic relationship at the interface between sapphire and α-Ta, which is crucial for determining the properties of the grown films. Perpendicular to the [11][12][13][14][15][16][17][18][19][20] direction, the Al 2 O 3 lattice is composed of alternating layers of Al and O. The Al layer itself can be described as flat, with every third atomic position along the [0001] direction being vacant, as shown in Fig.…”

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confidence: 99%

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Epitaxial α-Ta (110) film on a-plane sapphire substrate for superconducting qubits on wafer scale

Zhou,

Yang,

Wang

et al. 2023

Jpn. J. Appl. Phys.

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Realization of practical superconducting quantum computing requires many qubits of long coherence time. Compared to the commonly used Ta deposited on c-plane sapphire, which occasionally form α-Ta (111) grains and β-tantalum grains, high quality Ta (110) film can grow epitaxial on a-plane sapphire because of the atomic relationships at the interface. Well-ordered α-Ta (110) film on wafer-scale a-plane sapphire has been prepared. The film exhibits high residual resistance ratio. Transmon qubits fabricated using these film shows relaxation times exceeding 150 μs. The results suggest Ta film on a-plane sapphire is a promising choice for long coherence time qubit on wafer scale.

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Materials in superconducting quantum circuits

Cited by 11 publications

References 53 publications

A stable and low loss oxide layer on α-Ta (110) film for superconducting qubits

A stable and low loss oxide layer on α-Ta (110) film for superconducting qubits

Fabrication of Al/AlOx/Al junctions with high uniformity and stability on sapphire substrates

Epitaxial α-Ta (110) film on a-plane sapphire substrate for superconducting qubits on wafer scale

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