Sub-micrometer epitaxial Josephson junctions for quantum circuits

Kline, Jeffrey S.; Vissers, Michael; Silva, Fabio C. S. da; Wisbey, David; Weides, Martin; Weir, Terence J.; Turek, Benjamin; Braje, Danielle; Oliver, William; Shalibo, Yoni; Katz, Nadav; Johnson, Blake; Ohki, Thomas A.; Pappas, David P.

doi:10.1088/0953-2048/25/2/025005

Cited by 15 publications

(12 citation statements)

References 33 publications

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“…Yet another approach was taken by Kline et al (2012), who fabricated junctions with crystalline Sapphire (Al 2 O 3 ) barriers grown on an epitaxial Re/Ti multilayer base electrode. The multilayer was made by depositing 1.5 nm of Ti on 10 nm-thick layers of Re and repeating these steps 12 times.…”

Section: F Epitaxial Filmsmentioning

confidence: 99%

Towards understanding two-level-systems in amorphous solids: insights from quantum circuits

2019

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Amorphous solids show surprisingly universal behaviour at low temperatures. The prevailing wisdom is that this can be explained by the existence of two-state defects within the material. The so-called standard tunneling model has become the established framework to explain these results, yet it still leaves the central question essentially unanswered -what are these two-level defects? This question has recently taken on a new urgency with the rise of superconducting circuits in quantum computing, circuit quantum electrodynamics, magnetometry, electrometry and metrology. Superconducting circuits made from aluminium or niobium are fundamentally limited by losses due to two-level defects within the amorphous oxide layers encasing them. On the other hand, these circuits also provide a novel and effective method for studying the very defects which limit their operation. We can now go beyond ensemble measurements and probe individual defects -observing the quantum nature of their dynamics and studying their formation, their behaviour as a function of applied field, strain, temperature and other properties. This article reviews the plethora of recent experimental results in this area and discusses the various theoretical models which have been used to describe the observations. In doing so, it summarises the current approaches to solving this fundamentally important problem in solid-state physics.

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Section: F Epitaxial Filmsmentioning

confidence: 99%

Towards understanding two-level-systems in amorphous solids: insights from quantum circuits

2019

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“…For example, a multilayer of Re/Ti can be matched to a sapphire substrate and crystalline Al 2 O 3 can be used for the junction barrier. 172,173 Another option involves using NbN superconductors with an AlN barrier grown on MgO. 174 These systems have resulted in coherent operation, but fabricating robust structures with long-lived coherence remains elusive.…”

Section: [H1] Emerging Josephson Devicesmentioning

confidence: 99%

Engineering high-coherence superconducting qubits

Siddiqi

2021

Nat Rev Mater

170

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Advances in materials science and engineering have played a central role in the development of classical computers, and will undoubtedly be critical in propelling the maturation of quantum information technologies. In approaches to quantum computation based on superconducting circuits, as one goes from bulk materials to functional devices, amorphous insulating films and nonequilibrium excitations-electronic and phononic-are introduced, leading to dissipation and fluctuations that limit the computational power of state-of-the-art qubits and processors. In this Review, the major sources of decoherence in superconducting qubits are identified through an exploration of seminal qubit and resonator experiments. The proposed microscopic mechanisms associated with these imperfections are summarized, and directions for future research are discussed. The trade-offs between simple qubit primitives based on a single Josephson tunnel junction and more complex designs that use additional circuit elements, or new junction modalities, to reduce sensitivity to local noise sources are discussed, particularly in the context of materials optimization strategies for each architecture.

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“…There have been various studies on developing alternative multilayered fabrication methods [7]- [12] for large-scale integration of qubits. Trilayer junctions are particularly suitable for fabricating large-scale integrated circuits since they enable flexibility in the circuit layout.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Superconducting Qubits with Al Trilayer Josephson Junctions

Satoh

Noguchi

Yamagishi

et al. 2014

IEEE Trans. Appl. Supercond.

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To implement a large-scale integration of superconducting quantum bits (qubits), we have investigated a process of fabricating submicrometer Al/AlO x /Al trilayer Josephson junctions. Moreover, on the basis of this process, we developed a means of fabricating different kinds of superconducting qubits. Superconducting qubits require not only small junctions, but also peripheral circuit elements, such as a large resonator, on the same chip. As a result, we chose to use planarization in the self-aligned junction contact formation, which suppressed a pattern-areadependence of the chemical-mechanical polishing rate. In addition, Al fine wires with a width of 0.2 μm were required in some parts of the qubits to increase the coupling strength between the SQUIDs and qubits. We developed a two-step etching process to form such fine wires using i-line photoresist, which had a high etching resistance. The operation of three-junction flux qubits was confirmed in a dilution refrigerator.

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Sub-micrometer epitaxial Josephson junctions for quantum circuits

Cited by 15 publications

References 33 publications

Towards understanding two-level-systems in amorphous solids: insights from quantum circuits

Towards understanding two-level-systems in amorphous solids: insights from quantum circuits

Engineering high-coherence superconducting qubits

Fabrication of Superconducting Qubits with Al Trilayer Josephson Junctions

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