Material matters in superconducting qubits

Murray, Conal E.

doi:10.1016/j.mser.2021.100646

Cited by 51 publications

(32 citation statements)

References 341 publications

(552 reference statements)

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“…S7 we plot d c vs. B c for a sphere radius R YIG = 3 µm, assuming d w = 100 nm. A distance from the center of the magnet to the SQUID loop of d min = √ 2R YIG 4.2 µm would allow to use superconductors with critical field down to 120 mT, which is two orders of magnitude smaller than the critical magnetic field of NbTiN [84] used in highly coherent transmon qubit implementations [63,65,85]. Josephson junctions are typically made from aluminum and for a typical junction thickness ∼ 10 nm [63] the critical field is around 1 T [75].…”

Section: Critical Distancementioning

confidence: 99%

Analog quantum control of magnonic cat states on-a-chip by a superconducting qubit

Kounalakis,

Bauer,

Blanter

2022

Preprint

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We propose to directly and quantum-coherently couple a superconducting transmon qubit to magnons -the quanta of the collective spin excitations, in a nearby magnetic particle. The magnet's stray field couples to the qubit via a superconducting interference device (SQUID). We predict a resonant qubit-magnon exchange and a nonlinear radiation-pressure interaction that are both stronger than dissipation rates and tunable by an external flux bias. We additionally demonstrate a quantum control scheme that generates qubit-magnon entanglement and magnonic Schrödinger cat states with high fidelity.

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Section: Critical Distancementioning

confidence: 99%

Analog quantum control of magnonic cat states on-a-chip by a superconducting qubit

Kounalakis,

Bauer,

Blanter

2022

Preprint

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“…Although exciting and potentially disruptive, applications such as quantum simulations require a daunting amount of resources and complex infrastructures [3]. In contrast, an immediate application of superconducting devices is to use a single quantum circuit as a sensor for loss and noise processes in dielectric and superconducting materials [4]. Understanding such dissipative phenomena, which lead to quantum decoherence, is of paramount importance to further scale up quantum computers.…”

Section: Introductionmentioning

confidence: 99%

Fluctuation Spectroscopy of Two-Level Systems in Superconducting Resonators

Béjanin¹,

Ayadi²,

Xu³

et al. 2022

Preprint

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Superconducting quantum computing is experiencing a tremendous growth. Although major milestones have already been achieved, useful quantum-computing applications are hindered by a variety of decoherence phenomena. Decoherence due to two-level systems (TLSs) hosted by amorphous dielectric materials is ubiquitous in planar superconducting devices. We use high-quality quasilumped element resonators as quantum sensors to investigate TLS-induced loss and noise. We perform two-tone experiments with a probe and pump electric field; the pump is applied at different power levels and detunings. We measure and analyze time series of the quality factor and resonance frequency for very long time periods, up to 1000 h. We additionally carry out simulations based on the TLS interacting model in presence of a pump field. We find that loss and noise are reduced at medium and high power, matching the simulations, but not at low power.

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“…Silicon and sapphire are the current workhorse substrates for superconducting quantum devices [1,2]. As superconducting devices have advanced, material engineering has played a critical role in increasing resonator quality factor and qubit coherence time, with notable increases owing to the removal of disorder at device interfaces [3,4].…”

Section: Introductionmentioning

confidence: 99%

“…Likewise, new material systems are a testbed to explore microscopic origins of decoherence, ultimately leading to improved device function [1]. Currently, material and interfacial losses are the most prominent factors hindering the development of a useful quantum computer [2,7].…”

Section: Introductionmentioning

confidence: 99%

Ternary metal oxide substrates for superconducting circuits

Degnan¹,

He²,

Frieiro³

et al. 2022

Mater. Quantum. Technol.

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Substrate material imperfections and surface losses are one of the major factors limiting superconducting quantum circuitry from reaching the scale and complexity required to build a practical quantum computer. One potential path towards higher coherence of superconducting quantum devices is to explore new substrate materials with a reduced density of imperfections due to inherently diﬀerent surface chemistries. Here, we examine two ternary metal oxide materials, spinel (MgAl2O4) and lanthanum aluminate (LaAlO3), with a focus on surface and interface characterization and preparation. Devices fabricated on LaAlO3 have quality factors three times higher than those of earlier devices, which we attribute to a reduction in the interfacial disorder. MgAl2O4) is a new material in superconducting quantum devices, and even in the presence of signiﬁcant surface disorder, it consistently outperforms LaAlO3. Our results highlight the importance of materials exploration, substrate preparation, and characterization for identifying materials suitable for high-performance superconducting quantum circuitry.

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Material matters in superconducting qubits

Cited by 51 publications

References 341 publications

Analog quantum control of magnonic cat states on-a-chip by a superconducting qubit

Analog quantum control of magnonic cat states on-a-chip by a superconducting qubit

Fluctuation Spectroscopy of Two-Level Systems in Superconducting Resonators

Ternary metal oxide substrates for superconducting circuits

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