Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

arXiv:1807.00582 · Physical Review Applied

Tunable Nb Superconducting Resonator Based on a Constriction Nano-SQUID Fabricated with a Ne Focused Ion Beam

Oscar W. Kennedy, Jonathan Burnett, J. C. Fenton, N. G. N. Constantino, Paul A. Warburton, John J. L. Morton, Eva Dupont-Ferrier

Published Jan 4, 2019• 39 citations
arXivHTMLPDF

Abstract

Tunable resonators with high quality factors underpin the storage and retrieval of microwave-domain quantum information in spin ensembles used as long-lived quantum memories, and can enable multifrequency high-sensitivity electron spin resonance (ESR). The authors develop a single-layer technology, based on embedding nanoSQUIDs in superconducting niobium resonators, to realize high-quality frequency-tunable devices that are resilient to moderate magnetic fields. These devices will enable tunable-resonator-enhanced ESR protocols to be performed at specific fields and frequencies, such as storing quantum information in spins at low-decoherence ``clock transitions''.

DOI
10.1103/physrevapplied.11.014006

Related papers

Millikelvin Nb nanoSQUID-embedded tunable resonator fabricated with a neon focused-ion-beam

Jamie Potter, Laith Meti, Gemma Chapman +3 more

SQUID-embedded superconducting resonators are of great interest due to their potential for coupling highly scalable superconducting circuits with quantum memories based on solid-state spin ensembles. Such an application requires a high-Q, frequency-tunable resonator that is both resilient to magnetic field and able to operate at millikelvin temperatures. These requirements motivate the use of a higher Hc metal such as niobium; however, the challenge then becomes to sufficiently reduce the operating temperature. We address this by presenting a monolithic Nb nanoSQUID-embedded resonator, where neon focused-ion-beam fabrication of the nanoSQUID results in a device displaying frequency tunability at T=16 mK. In order to assess the applicability of the device for coupling to small spin clusters, we characterize the flux sensitivity as a function of microwave drive power and externally applied magnetic field and find that the noise is dominated by dielectric noise in the resonator. Finally, we discuss improvements to the device design that can dramatically improve the flux sensitivity, which highlights the promise of Nb SQUID-embedded resonators for hybrid superconductor-spin applications.

arXiv:2412.16045•Applied Physics Letters•Jan 3, 2025•5 citations

Tuning high-Q superconducting resonators by magnetic field reorientation

Christoph W. Zollitsch, James O’Sullivan, Oscar W. Kennedy +2 more

Superconducting resonators interfaced with paramagnetic spin ensembles are used to increase the sensitivity of electron spin resonance experiments and are key elements of microwave quantum memories. Certain spin systems that are promising for such quantum memories possess “sweet spots” at particular combinations of magnetic fields and frequencies, where spin coherence times or linewidths become particularly favorable. In order to be able to couple high-Q superconducting resonators to such specific spin transitions, it is necessary to be able to tune the resonator frequency under a constant magnetic field amplitude. Here, we demonstrate a high-quality, magnetic field resilient superconducting resonator, using a 3D vector magnet to continuously tune its resonance frequency by adjusting the orientation of the magnetic field. The resonator maintains a quality factor of >105 up to magnetic fields of 2.6 T, applied predominantly in the plane of the superconductor. We achieve a continuous tuning of up to 30 MHz by rotating the magnetic field vector, introducing a component of 5 mT perpendicular to the superconductor.

arXiv:1909.11020•AIP Advances•Dec 1, 2019•31 citations

Tuning high-Q superconducting resonators by magnetic field reorientation

Zollitsch, CW, James O’Sullivan, Oscar W. Kennedy +2 more

ABSTRACT \nSuperconducting resonators interfaced with paramagnetic spin ensembles are used to increase the sensitivity of electron spin resonance experiments and are key elements of microwave quantum memories. Certain spin systems that are promising for such quantum memories possess “sweet spots” at particular combinations of magnetic fields and frequencies, where spin coherence times or linewidths become particularly favorable. In order to be able to couple high-Q superconducting resonators to such specific spin transitions, it is necessary to be able to tune the resonator frequency under a constant magnetic field amplitude. Here, we demonstrate a high-quality, magnetic field resilient superconducting resonator, using a 3D vector magnet to continuously tune its resonance frequency by adjusting the orientation of the magnetic field. The resonator maintains a quality factor of >10^{5} up to magnetic fields of 2.6 T, applied predominantly in the plane of the superconductor. We achieve a continuous tuning of up to 30 MHz by rotating the magnetic field vector, introducing a component of 5 mT perpendicular to the superconductor.

•Dec 1, 2019•2 citations

Coupling superconducting resonators to bismuth donor spins in silicon for quantum memory applications

James O’Sullivan

Spins in nuclear-spin-free solid state systems such as isotopically purified 28Si have seen extensive research as candidates for quantum information storage and processing, thanks to their long spin coherence lifetimes [1]. Strongly coupling such spins to a high Q superconducting resonator provides a route to develop microwave quantum memories. Bismuth donor spins can be tuned to so-called ‘clock transitions’, which, due to their insensitivity to magnetic field noise, can have electron spin coherence times as long as 3 seconds [2]. The system also possesses ‘hyperfine clock transitions’, which are insensitive to changes in the hyperfine coupling constant, and which may mitigate the effects of strain on the transition. Achieving coupling to such transitions requires resonators which are both magnetic-field resilient, and frequency tuneable. This thesis outlines the work done towards realising a quantum memory using Bi donors in silicon, from resonator design and fabrication, coupling these to implanted Bi spins in silicon and tuning to various clock transitions, through to storage and retrieval of few-photon excitations in a spin ensemble and their retrieval over 100 ms later.

•Jan 1, 2020•0 citations

Multi-frequency spin manipulation using rapidly tunable superconducting coplanar waveguide microresonators

A. T. Asfaw, A. J. Sigillito, A. M. Tyryshkin +2 more

In this work, we demonstrate the use of frequency-tunable superconducting NbTiN coplanar waveguide microresonators for multi-frequency pulsed electron spin resonance (ESR) experiments. By applying a bias current to the center pin, the resonance frequency (∼7.6 GHz) can be continuously tuned by as much as 95 MHz in 270 ns without a change in the quality factor of 3000 at 2 K. We demonstrate the ESR performance of our resonators by measuring donor spin ensembles in silicon and show that adiabatic pulses can be used to overcome magnetic field inhomogeneities and microwave power limitations due to the applied bias current. We take advantage of the rapid tunability of these resonators to manipulate both phosphorus and arsenic spins in a single pulse sequence, demonstrating pulsed double electron-electron resonance. Our NbTiN resonator design is useful for multi-frequency pulsed ESR and should also have applications in experiments where spin ensembles are used as quantum memories.

arXiv:1705.02413•Applied Physics Letters•Jul 17, 2017•23 citations

Microwave Inductive Readout of EBL Nanobridge SQUIDs

Tom Godfrey, George Long, John C. Gallop +5 more

Niobium-based nanobridge superconducting quantum interference devices (SQUIDs) have shown very low noise performance and high-frequency operation. We describe how we are bringing together these two aspects of nanobridge SQUIDs with the aim of realizing single spin-flip detection using microwave inductive readout techniques, where the nanobridge SQUID is integrated into a superconducting coplanar waveguide resonator. Using electron beam lithography (EBL) is ideal for fabricating nanobridge junctions and has the advantage of being easily scalable compared to using a focused ion beam. In this article, we demonstrate that EBL is suitable for fabricating nanobridge junction SQUIDs, and they exhibit very comparable performance to previous focused ion beam milled SQUIDs. Our integrated devices show potential to be used for flux-tunable sensors.

IEEE Transactions on Applied Superconductivity•May 28, 2020•3 citations
Tunable resonators with high quality factors underpin the storage and retrieval of microwave-domain quantum information in spin ensembles used as long-lived quantum memories, and can enable multifrequency high-sensitivity electron spin resonance (ESR). The authors develop a single-layer technology, based on embedding nanoSQUIDs in superconducting niobium resonators, to realize high-quality frequency-tunable devices that are resilient to moderate magnetic fields. These devices will enable tunable-resonator-enhanced ESR protocols to be performed at specific fields and frequencies, such as storing quantum information in spins at low-decoherence ``clock transitions''.
SQUID-embedded superconducting resonators are of great interest due to their potential for coupling highly scalable superconducting circuits with quantum memories based on solid-state spin ensembles. Such an application requires a high-Q, frequency-tunable resonator that is both resilient to magnetic field and able to operate at millikelvin temperatures. These requirements motivate the use of a higher Hc metal such as niobium; however, the challenge then becomes to sufficiently reduce the operating temperature. We address this by presenting a monolithic Nb nanoSQUID-embedded resonator, where neon focused-ion-beam fabrication of the nanoSQUID results in a device displaying frequency tunability at T=16 mK. In order to assess the applicability of the device for coupling to small spin clusters, we characterize the flux sensitivity as a function of microwave drive power and externally applied magnetic field and find that the noise is dominated by dielectric noise in the resonator. Finally, we discuss improvements to the device design that can dramatically improve the flux sensitivity, which highlights the promise of Nb SQUID-embedded resonators for hybrid superconductor-spin applications.
Superconducting resonators interfaced with paramagnetic spin ensembles are used to increase the sensitivity of electron spin resonance experiments and are key elements of microwave quantum memories. Certain spin systems that are promising for such quantum memories possess “sweet spots” at particular combinations of magnetic fields and frequencies, where spin coherence times or linewidths become particularly favorable. In order to be able to couple high-Q superconducting resonators to such specific spin transitions, it is necessary to be able to tune the resonator frequency under a constant magnetic field amplitude. Here, we demonstrate a high-quality, magnetic field resilient superconducting resonator, using a 3D vector magnet to continuously tune its resonance frequency by adjusting the orientation of the magnetic field. The resonator maintains a quality factor of >105 up to magnetic fields of 2.6 T, applied predominantly in the plane of the superconductor. We achieve a continuous tuning of up to 30 MHz by rotating the magnetic field vector, introducing a component of 5 mT perpendicular to the superconductor.
ABSTRACT \nSuperconducting resonators interfaced with paramagnetic spin ensembles are used to increase the sensitivity of electron spin resonance experiments and are key elements of microwave quantum memories. Certain spin systems that are promising for such quantum memories possess “sweet spots” at particular combinations of magnetic fields and frequencies, where spin coherence times or linewidths become particularly favorable. In order to be able to couple high-Q superconducting resonators to such specific spin transitions, it is necessary to be able to tune the resonator frequency under a constant magnetic field amplitude. Here, we demonstrate a high-quality, magnetic field resilient superconducting resonator, using a 3D vector magnet to continuously tune its resonance frequency by adjusting the orientation of the magnetic field. The resonator maintains a quality factor of >10^{5} up to magnetic fields of 2.6 T, applied predominantly in the plane of the superconductor. We achieve a continuous tuning of up to 30 MHz by rotating the magnetic field vector, introducing a component of 5 mT perpendicular to the superconductor.
Spins in nuclear-spin-free solid state systems such as isotopically purified 28Si have seen extensive research as candidates for quantum information storage and processing, thanks to their long spin coherence lifetimes [1]. Strongly coupling such spins to a high Q superconducting resonator provides a route to develop microwave quantum memories. Bismuth donor spins can be tuned to so-called ‘clock transitions’, which, due to their insensitivity to magnetic field noise, can have electron spin coherence times as long as 3 seconds [2]. The system also possesses ‘hyperfine clock transitions’, which are insensitive to changes in the hyperfine coupling constant, and which may mitigate the effects of strain on the transition. Achieving coupling to such transitions requires resonators which are both magnetic-field resilient, and frequency tuneable. This thesis outlines the work done towards realising a quantum memory using Bi donors in silicon, from resonator design and fabrication, coupling these to implanted Bi spins in silicon and tuning to various clock transitions, through to storage and retrieval of few-photon excitations in a spin ensemble and their retrieval over 100 ms later.
In this work, we demonstrate the use of frequency-tunable superconducting NbTiN coplanar waveguide microresonators for multi-frequency pulsed electron spin resonance (ESR) experiments. By applying a bias current to the center pin, the resonance frequency (∼7.6 GHz) can be continuously tuned by as much as 95 MHz in 270 ns without a change in the quality factor of 3000 at 2 K. We demonstrate the ESR performance of our resonators by measuring donor spin ensembles in silicon and show that adiabatic pulses can be used to overcome magnetic field inhomogeneities and microwave power limitations due to the applied bias current. We take advantage of the rapid tunability of these resonators to manipulate both phosphorus and arsenic spins in a single pulse sequence, demonstrating pulsed double electron-electron resonance. Our NbTiN resonator design is useful for multi-frequency pulsed ESR and should also have applications in experiments where spin ensembles are used as quantum memories.
Niobium-based nanobridge superconducting quantum interference devices (SQUIDs) have shown very low noise performance and high-frequency operation. We describe how we are bringing together these two aspects of nanobridge SQUIDs with the aim of realizing single spin-flip detection using microwave inductive readout techniques, where the nanobridge SQUID is integrated into a superconducting coplanar waveguide resonator. Using electron beam lithography (EBL) is ideal for fabricating nanobridge junctions and has the advantage of being easily scalable compared to using a focused ion beam. In this article, we demonstrate that EBL is suitable for fabricating nanobridge junction SQUIDs, and they exhibit very comparable performance to previous focused ion beam milled SQUIDs. Our integrated devices show potential to be used for flux-tunable sensors.