Probing defect densities at the edges and inside Josephson junctions of superconducting qubits

• URL: http://arxiv.org/abs/2108.06555v2
• Date: Mon, 7 Mar 2022 14:00:22 GMT
• Title: Probing defect densities at the edges and inside Josephson junctions of superconducting qubits
• Authors: Alexander Bilmes, Serhii Volosheniuk, Alexey V. Ustinov, and J\"urgen Lisenfeld
• Abstract summary: Tunneling defects in disordered materials form spurious two-level systems. For superconducting qubits, defects in tunnel barriers of submicrometer-sized Josephson junctions couple strongest to the qubit. We investigate whether defects appear predominantly at the edges or deep within the amorphous tunnel barrier of a junction.
• Score: 58.720142291102135
• License: http://creativecommons.org/licenses/by-sa/4.0/
• Abstract: Tunneling defects in disordered materials form spurious two-level systems which are a major source of decoherence for micro-fabricated quantum devices. For superconducting qubits, defects in tunnel barriers of submicrometer-sized Josephson junctions couple strongest to the qubit, which necessitates optimization of the junction fabrication to mitigate defect formation. Here, we investigate whether defects appear predominantly at the edges or deep within the amorphous tunnel barrier of a junction. For this, we compare defect densities in differently shaped Al/AlO$_x$/Al Josephson junctions that are part of a Transmon qubit. We observe that the number of detectable junction-defects is proportional to the junction area, and does not significantly scale with the junction's circumference, which proposes that defects are evenly distributed inside the tunnel barrier. Moreover, we find very similar defect densities in thermally grown tunnel barriers that were formed either directly after the base electrode was deposited, or in a separate deposition step after removal of native oxide by Argon ion milling.

Related papers

• The influence of pinholes and weak-points in aluminium-oxide Josephson junctions [0.0]
  Josephson junctions are the key components used in superconducting qubits for quantum computing. Pinholes in the junction have been suggested as one of the possible contributors to these instabilities. We use molecular dynamics to create three-dimensional atomistic models to describe Al-AlOx-Al tunnel junctions.
  arXiv  Detail & Related papers  (2023-11-27T06:13:39Z)
• Quasiparticles in superconducting qubits with asymmetric junctions [0.0]
  We consider quasiparticle effects in superconducting qubits to account for asymmetry in the gap on the two sides of a Josephson junction. We find that different regimes can be encountered in which the quasiparticles have either similar densities in the two junction leads, or are largely confined to the lower-gap lead.
  arXiv  Detail & Related papers  (2022-05-12T12:43:42Z)
• Review on coherent quantum emitters in hexagonal boron nitride [91.3755431537592]
  I discuss the state-of-the-art of defect centers in hexagonal boron nitride with a focus on optically coherent defect centers. The spectral transition linewidth remains unusually narrow even at room temperature. The field is put into a broad perspective with impact on quantum technology such as quantum optics, quantum photonics as well as spin optomechanics.
  arXiv  Detail & Related papers  (2022-01-31T12:49:43Z)
• Quasiparticle tunneling as a probe of Josephson junction barrier and capacitor material in superconducting qubits [2.6549320605996862]
  Non-equilibrium quasiparticles are possible sources for decoherence in superconducting qubits because they can lead to energy decay or dephasing upon tunneling across Josephson junctions (JJs) Here, we investigate the impact of the intrinsic properties of two-dimensional transmon qubits on quasiparticle tunneling (QPT) We find the tunneling rate of the nonequilibrium quasiparticles to be sensitive to the choice of the shunting capacitor material and their geometry in qubits.
  arXiv  Detail & Related papers  (2021-06-22T02:33:59Z)
• In-situ bandaged Josephson junctions for superconducting quantum processors [101.18253437732933]
  Shadow evaporation is commonly used to micro-fabricate the key element of superconducting qubits - the Josephson junction. Here, we present an improved shadow evaporation technique allowing one to fabricate sub-micrometer-sized Josephson junctions together with bandage layers in a single lithography step.
  arXiv  Detail & Related papers  (2021-01-05T11:08:09Z)
• Quantum Sensors for Microscopic Tunneling Systems [58.720142291102135]
  tunneling Two-Level-Systems (TLS) are important for micro-fabricated quantum devices such as superconducting qubits. We present a method to characterize individual TLS in virtually arbitrary materials deposited as thin-films. Our approach opens avenues for quantum material spectroscopy to investigate the structure of tunneling defects.
  arXiv  Detail & Related papers  (2020-11-29T09:57:50Z)
• Coherent superconducting qubits from a subtractive junction fabrication process [48.7576911714538]
  Josephson tunnel junctions are the centerpiece of almost any superconducting electronic circuit, including qubits. In recent years, sub-micron scale overlap junctions have started to attract attention. This work paves the way towards a more standardized process flow with advanced materials and growth processes, and constitutes an important step for large scale fabrication of superconducting quantum circuits.
  arXiv  Detail & Related papers  (2020-06-30T14:52:14Z)
• Mechanical Decoupling of Quantum Emitters in Hexagonal Boron Nitride from Low-Energy Phonon Modes [52.77024349608834]
  Quantum emitters in hexagonal Boron Nitride (hBN) were recently reported to hol a homogeneous linewidth according to the Fourier-Transform limit up to room temperature. This unusual observation was traced back to decoupling from in-plane phonon modes which can arise if the emitter is located between two planes of the hBN host material.
  arXiv  Detail & Related papers  (2020-04-22T20:00:49Z)
• Transparent Gatable Superconducting Shadow Junctions [2.396595761899586]
  Gate junctions are key elements in quantum devices based on hybrid semiconductor-superconductor materials. We grow single crystalline InAs, InSb and $mathrmInAs_1-xSb_x$ nanowires with epitaxial superconductors and in-situ shadowed junctions in a single-step molecular beam epitaxy process.
  arXiv  Detail & Related papers  (2020-03-10T01:36:12Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.