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:2511.19197

YBa$_2$Cu$_3$O$_7$ nano-constriction Josephson junctions and SQUIDs fabricated by focused helium-ion-beam irradiation

Christoph Schmid, Christopher Buckreus, David Haas, Max Pröpper, Robin Hutt, César Magén, Dominik Hanisch, Max Karrer, Meinhard Schilling, Dieter Koelle, Reinhold Kleiner, Edward Goldobin

cond-mat.supr-conquant-phSubmitted Nov 24, 2025• Announced Nov 25, 2025• 0 citations
arXivHTMLPDF

Abstract

By focused $30\,\mathrm{keV}$ He ion beam irradiation, epitaxially grown YBa$_2$Cu$_3$O$_7$ (YBCO) thin films can be driven from the superconducting to the insulating state with increasing irradiation dose. A properly chosen dose suppresses superconductivity down to $4\,\mathrm{K}$, while crystallinity is still preserved. With this approach we create areas of normal-conducting YBCO that can be used to define resistively shunted constriction-type Josephson junctions (cJJs) on the nanometer scale. We also demonstrate that the fabricated cJJs can be incorporated in direct current superconducting quantum interference devices and can be used as detector junctions in THz antennas.

Related papers

Tuning Y–Ba–Cu–O Focused Helium Ion Beam Josephson Junctions for Use as THz Mixers

Anthony Cortez, Ethan Y. Cho, Hao Li +3 more

We present Josephson junctions fabricated from high transition temperature superconductor YBa2Cu3O7coupled to spiral THz antennas. The fabrication process involves creating a Josephson junction at the center of a superconducting bridge embedded into a THz spiral antenna using irradiation from a focused helium ion beam. For low doses of helium irradiation, the junctions have metallic barriers and operate at temperatures as high as 67 K. For higher doses of irradiation, insulator barriers are created. These devices have higher resistance but require cooling to lower temperatures (~10 K) due to smaller critical currents. Through optimization of the dose and by trimming the width of the junctions, we have created high resistance devices to improve the impedance match to a spiral antenna. Under 90-GHz radiation, we observe up to 17 Shapiro steps in the I-V curve out to approximately 3 mV at a temperature of 10 K.

IEEE Transactions on Applied Superconductivity•Mar 18, 2019•12 citations

YBa2Cu3O7− δ superconducting quantum interference devices with metallic to insulating barriers written with a focused helium ion beam

Ethan Y. Cho, M. K., Chuong Huynh +5 more

In this work, we demonstrate the ability to fabricate superconducting quantum interference devices (SQUIDs) by directly writing Josephson junctions into the plane of YBa2Cu3O7−δ thin films with a focused helium ion beam. This technique allows for the control of the Josephson barrier transport properties through the single parameter, ion dose. SQUIDs written with a dose of 4 × 1016 ions/cm2 had metallic barrier junctions that exhibited nearly ideal electrical transport characteristics at 50 K and a flux noise of 20 μΦ0/Hz at 10 Hz. At higher irradiation doses, the SQUIDs had insulating barrier Josephson junctions with a quasi particle energy gap edge at 20 meV.

Applied Physics Letters•Jun 22, 2015•69 citations

Dynamic properties of high-Tc superconducting nano-junctions made with a focused helium ion beam

F. Couëdo, P. Amari, C. Feuillet-Palma +5 more

Abstract The Josephson junction (JJ) is the corner stone of superconducting electronics and quantum information processing. While the technology for fabricating low T c JJ is mature and delivers quantum circuits able to reach the “quantum supremacy”, the fabrication of reproducible and low-noise high- T c JJ is still a challenge to be taken up. Here we report on noise properties at RF frequencies of recently introduced high- T c Josephson nano-junctions fabricated by mean of a Helium ion beam focused at sub-nanometer scale on a YBa 2 Cu 3 O 7 thin film. We show that their current-voltage characteristics follow the standard Resistively-Shunted-Junction (RSJ) circuit model, and that their characteristic frequency f c = (2 e / h ) I c R n reaches ~300 GHz at low temperature. Using the “detector response” method, we evidence that the Josephson oscillation linewidth is only limited by the thermal noise in the RSJ model for temperature ranging from T ~ 20 K to 75 K. At lower temperature and for the highest He irradiation dose, the shot noise contribution must also be taken into account when approaching the tunneling regime. We conclude that these Josephson nano-junctions present the lowest noise level possible, which makes them very promising for future applications in the microwave and terahertz regimes.

arXiv:1908.11163•Scientific Reports•Jun 24, 2020•23 citations

High-Frequency Properties of Y-Ba-Cu-O Josephson Junctions Fabricated with Helium Ion Beam Irradiation

Anthony Cortez, Ethan Y. Cho, Hao Li +3 more

We have fabricated spiral THz antennas containing embedded high TCYBa2Cu3O7 (YBCO) focused helium ion beam Josephson junctions (JJ) for characterization of their high frequency characteristics. The values of the resistance and critical current of the junctions are controlled through the irradiation dose and geometry of the junction. We observe several orders of Shapiro steps in the current voltage characteristics of the device when irradiated with 0.6 THz and a single step when irradiated at 2.52 THz.

IEEE International Superconductive Electronics Conference (ISEC)•Jul 1, 2019•2 citations

Highly tunable NbTiN Josephson junctions fabricated with focused helium ion beam

Aki Ruhtinas, Ilari J. Maasilta

We demonstrate a direct writing method for the fabrication of planar Josephson junctions from high-quality superconducting niobium titanium nitride (NbTiN) thin films, by creating local disorder using focused He ion beam irradiation. We control the suppression of superconductivity in NbTiN as a function of the helium ion beam fluence, enabling us to successfully fabricate Josephson junctions with highly tunable weak links ranging from the metallic to the insulating phase, utilizing the continuous nature of the disorder-induced superconductor-insulator transition. We demonstrate the successful fabrication of both superconductor-normal metal-superconductor (SNS) and superconductor-insulator-superconductor (SIS) type of devices, and show that we can achieve an exceptionally wide range ( ∼ 5 orders of magnitude) of critical current densities and junction resistances. The SNS-type junctions follow closely the ideal resistively and capacitively shunted junction behavior, have high characteristic voltages up to ∼ 1.5 mV , and show Shapiro steps up to very high orders, while the SIS junctions also follow established theories well. The results suggest that the junctions are suitable for a wide range of applications in superconducting electronics because of the excellent mechanical, electrical, and microwave properties of NbTiN. In particular, as NbTiN has previously been used to fabricate high-quality factor microwave resonators, we see the method as a promising and simple way to realize high-frequency superconducting qubits and other quantum devices using only a single superconducting film.

arXiv:2303.17348•Physical Review Research•Oct 28, 2025•3 citations

High- T c radio-frequency superconducting quantum interference devices fabricated from YBa 2 Cu 3 O 7-δ using focused helium ion beam technique

Ziwen 紫雯 Chen 陈, Yulong Li, Yan Zhang +3 more

Abstract The reliable fabrication of high-sensitivity superconducting quantum interference devices (SQUIDs) with high critical transition temperature (high- T c ) is crucial for many practical applications such as weak magnetic sensing. In this work, we report the first realization of the YBa 2 Cu 3 O 7− δ (YBCO) radio frequency SQUIDs (rf SQUIDs) based on focused helium ion beam (FHIB) technique. A series of YBCO rf SQUIDs with high consistency were fabricated using a 30 keV FHIB with different helium ion (He + ) dose. The dose-dependent characteristics of the fabricated devices were systematically investigated at a temperature of 77 K. The experimental results verify that the variation in He + dose can effectively modulate the junction parameters and thereby the device noise performance. A non-monotonic white noise trend with increasing He + dose was observed, which could be primarily attributed to the transition of operational working regime of the fabricated rf SQUIDs. Based upon the dose optimization, a flux noise of 58 μ Φ 0 / H z 1 / 2 , corresponding to a field sensitivity of 185 f T / H z 1 / 2 , was achieved with our current device configuration. Approaches to further optimize the overall device performance are also discussed. Our work demonstrates FHIB-based high- T c SQUIDs with high junction parameter consistency a promising candidate for the implementation of multi-channel weak magnetic field detection systems and might hopefully serve as a platform for validating the theoretical models of high- T c SQUIDs.

Superconductor Science and Technology•Oct 1, 2026•0 citations
YBa2_22​Cu3_33​O7_77​ nano-constriction Josephson junctions and SQUIDs fabricated by focused helium-ion-beam irradiation
By focused 30 keV30\,\mathrm{keV}30keV He ion beam irradiation, epitaxially grown YBa2_22​Cu3_33​O7_77​ (YBCO) thin films can be driven from the superconducting to the insulating state with increasing irradiation dose. A properly chosen dose suppresses superconductivity down to 4 K4\,\mathrm{K}4K, while crystallinity is still preserved. With this approach we create areas of normal-conducting YBCO that can be used to define resistively shunted constriction-type Josephson junctions (cJJs) on the nanometer scale. We also demonstrate that the fabricated cJJs can be incorporated in direct current superconducting quantum interference devices and can be used as detector junctions in THz antennas.
We present Josephson junctions fabricated from high transition temperature superconductor YBa2Cu3O7coupled to spiral THz antennas. The fabrication process involves creating a Josephson junction at the center of a superconducting bridge embedded into a THz spiral antenna using irradiation from a focused helium ion beam. For low doses of helium irradiation, the junctions have metallic barriers and operate at temperatures as high as 67 K. For higher doses of irradiation, insulator barriers are created. These devices have higher resistance but require cooling to lower temperatures (~10 K) due to smaller critical currents. Through optimization of the dose and by trimming the width of the junctions, we have created high resistance devices to improve the impedance match to a spiral antenna. Under 90-GHz radiation, we observe up to 17 Shapiro steps in the I-V curve out to approximately 3 mV at a temperature of 10 K.
In this work, we demonstrate the ability to fabricate superconducting quantum interference devices (SQUIDs) by directly writing Josephson junctions into the plane of YBa2Cu3O7−δ thin films with a focused helium ion beam. This technique allows for the control of the Josephson barrier transport properties through the single parameter, ion dose. SQUIDs written with a dose of 4 × 1016 ions/cm2 had metallic barrier junctions that exhibited nearly ideal electrical transport characteristics at 50 K and a flux noise of 20 μΦ0/Hz at 10 Hz. At higher irradiation doses, the SQUIDs had insulating barrier Josephson junctions with a quasi particle energy gap edge at 20 meV.
Abstract The Josephson junction (JJ) is the corner stone of superconducting electronics and quantum information processing. While the technology for fabricating low T c JJ is mature and delivers quantum circuits able to reach the “quantum supremacy”, the fabrication of reproducible and low-noise high- T c JJ is still a challenge to be taken up. Here we report on noise properties at RF frequencies of recently introduced high- T c Josephson nano-junctions fabricated by mean of a Helium ion beam focused at sub-nanometer scale on a YBa 2 Cu 3 O 7 thin film. We show that their current-voltage characteristics follow the standard Resistively-Shunted-Junction (RSJ) circuit model, and that their characteristic frequency f c = (2 e / h ) I c R n reaches ~300 GHz at low temperature. Using the “detector response” method, we evidence that the Josephson oscillation linewidth is only limited by the thermal noise in the RSJ model for temperature ranging from T ~ 20 K to 75 K. At lower temperature and for the highest He irradiation dose, the shot noise contribution must also be taken into account when approaching the tunneling regime. We conclude that these Josephson nano-junctions present the lowest noise level possible, which makes them very promising for future applications in the microwave and terahertz regimes.
We have fabricated spiral THz antennas containing embedded high TCYBa2Cu3O7 (YBCO) focused helium ion beam Josephson junctions (JJ) for characterization of their high frequency characteristics. The values of the resistance and critical current of the junctions are controlled through the irradiation dose and geometry of the junction. We observe several orders of Shapiro steps in the current voltage characteristics of the device when irradiated with 0.6 THz and a single step when irradiated at 2.52 THz.
We demonstrate a direct writing method for the fabrication of planar Josephson junctions from high-quality superconducting niobium titanium nitride (NbTiN) thin films, by creating local disorder using focused He ion beam irradiation. We control the suppression of superconductivity in NbTiN as a function of the helium ion beam fluence, enabling us to successfully fabricate Josephson junctions with highly tunable weak links ranging from the metallic to the insulating phase, utilizing the continuous nature of the disorder-induced superconductor-insulator transition. We demonstrate the successful fabrication of both superconductor-normal metal-superconductor (SNS) and superconductor-insulator-superconductor (SIS) type of devices, and show that we can achieve an exceptionally wide range ( ∼ 5 orders of magnitude) of critical current densities and junction resistances. The SNS-type junctions follow closely the ideal resistively and capacitively shunted junction behavior, have high characteristic voltages up to ∼ 1.5 mV , and show Shapiro steps up to very high orders, while the SIS junctions also follow established theories well. The results suggest that the junctions are suitable for a wide range of applications in superconducting electronics because of the excellent mechanical, electrical, and microwave properties of NbTiN. In particular, as NbTiN has previously been used to fabricate high-quality factor microwave resonators, we see the method as a promising and simple way to realize high-frequency superconducting qubits and other quantum devices using only a single superconducting film.
Abstract The reliable fabrication of high-sensitivity superconducting quantum interference devices (SQUIDs) with high critical transition temperature (high- T c ) is crucial for many practical applications such as weak magnetic sensing. In this work, we report the first realization of the YBa 2 Cu 3 O 7− δ (YBCO) radio frequency SQUIDs (rf SQUIDs) based on focused helium ion beam (FHIB) technique. A series of YBCO rf SQUIDs with high consistency were fabricated using a 30 keV FHIB with different helium ion (He + ) dose. The dose-dependent characteristics of the fabricated devices were systematically investigated at a temperature of 77 K. The experimental results verify that the variation in He + dose can effectively modulate the junction parameters and thereby the device noise performance. A non-monotonic white noise trend with increasing He + dose was observed, which could be primarily attributed to the transition of operational working regime of the fabricated rf SQUIDs. Based upon the dose optimization, a flux noise of 58 μ Φ 0 / H z 1 / 2 , corresponding to a field sensitivity of 185 f T / H z 1 / 2 , was achieved with our current device configuration. Approaches to further optimize the overall device performance are also discussed. Our work demonstrates FHIB-based high- T c SQUIDs with high junction parameter consistency a promising candidate for the implementation of multi-channel weak magnetic field detection systems and might hopefully serve as a platform for validating the theoretical models of high- T c SQUIDs.