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

Science Advances

In situ amplification of spin echoes within a kinetic inductance parametric amplifier

Wyatt Vine, Mykhailo Savytskyi, Arjen Vaartjes, Anders Kringhøj, Daniel J. Parker, James Slack-Smith, Thomas Schenkel, Klaus Mølmer, Jeffrey Colin McCallum, Brett C. Johnson, Andrea Morello, Jarryd J. Pla

Published Mar 10, 2023• 22 citations
Publisher

Abstract

The use of superconducting microresonators together with quantum-limited Josephson parametric amplifiers has enhanced the sensitivity of pulsed electron spin resonance (ESR) measurements by more than four orders of magnitude. So far, the microwave resonators and amplifiers have been designed as separate components due to the incompatibility of Josephson junction–based devices with magnetic fields. This has produced complex spectrometers and raised technical barriers toward adoption of the technique. Here, we circumvent this issue by coupling an ensemble of spins directly to a weakly nonlinear and magnetic field–resilient superconducting microwave resonator. We perform pulsed ESR measurements with a 1-pL mode volume containing 6 × 10 7 spins and amplify the resulting signals within the device. When considering only those spins that contribute to the detected signals, we find a sensitivity of 2.8 × 1 0 3 spins / Hz for a Hahn echo sequence at a temperature of 400 mK. In situ amplification is demonstrated at fields up to 254 mT, highlighting the technique’s potential for application under conventional ESR operating conditions.

DOI
10.1126/sciadv.adg1593

Related papers

In-situ amplification of spin echoes within a kinetic inductance parametric amplifier

Wyatt Vine, Mykhailo Savytskyi, Daniel Parker +6 more

The use of superconducting micro-resonators in combination with quantum-limited Josephson parametric amplifiers has in recent years lead to more than four orders of magnitude improvement in the sensitivity of pulsed Electron Spin Resonance (ESR) measurements. So far, the microwave resonators and amplifiers have been designed as separate components, largely due to the incompatibility of Josephson junction-based devices with even moderate magnetic fields. This has led to complex spectrometers that operate under strict environments, creating technical barriers for the widespread adoption of the technique. Here we circumvent this issue by inductively coupling an ensemble of spins directly to a weakly nonlinear microwave resonator, which is engineered from a magnetic field-resilient thin superconducting film. We perform pulsed ESR measurements with a $1$~pL effective mode volume and amplify the resulting spin signal using the same device, ultimately achieving a sensitivity of $2.8 \times 10^3$ spins in a single-shot Hahn echo measurement at a temperature of 400 mK. We demonstrate the combined functionalities at fields as large as 254~mT, highlighting the technique's potential for application under more conventional ESR operating conditions.

arXiv:2211.11333•Nov 21, 2022•0 citations

Magnetic Field-Resilient Quantum-Limited Parametric Amplifier

Mingrui Xu, Risheng Cheng, Yufeng Wu +2 more

Superconducting parametric amplifiers are crucial components in microwave quantum circuits for enabling quantum-limited signal readout.The best-performing such amplifiers are often based on Josephson junctions, which however are sensitive to magnetic fields.Therefore, they require magnetic shields and are not easily integratable with other quantum systems that operate within magnetic fields, such as spinensemble quantum memories.To tackle this challenge, we develop a kinetic inductance-based parametric amplifier featuring a NbN nanobridge instead of Josephson junctions, which provides the desired nonlinearity for a strong parametric gain up to 42 dB.The added noise of this nanobridge kinetic-inductance parametric amplifier (hereby referred to as NKPA) is calibrated and found to be 0.59 ± 0.03 quanta for phase-preserving amplification, approaching the quantum limit of 0.5 quanta.Most importantly, we show that such excellent noise performance is preserved in an in-plane magnetic field up to 427 mT, the maximum field available in our experiment.This magnetic-field-resilient parametric amplifier presents an opportunity towards addressing single electron-spin resonance and more efficient search for axions as well as Majorana fermions.

arXiv:2209.13652•PRX Quantum•Feb 28, 2023•49 citations

Hybridized-Mode Parametric Amplifier in Kinetic-Inductance Circuits

Danial Davoudi, Abdul Mohamed, Shabir Barzanjeh

Parametric amplification is essential for quantum measurement, enabling the amplification of weak microwave signals with minimal added noise. While Josephson-junction-based amplifiers have become standard in superconducting quantum circuits, their magnetic sensitivity, limited saturation power, and sub-kelvin operating requirements motivate the development of alternative nonlinear platforms. Here we demonstrate a two-mode kinetic-inductance parametric amplifier based on a pair of capacitively coupled Kerr-nonlinear resonators fabricated from NbTiN and NbN thin films. The distributed Kerr nonlinearity of these materials enables nondegenerate four-wave-mixing amplification with gains approaching 40 dB, gain-bandwidth products up to 6.9 MHz, and 1-dB compression powers two to three orders of magnitude higher than those of state-of-the-art Josephson amplifiers. A coupled-mode theoretical model accurately captures the pump-induced modification of the hybridized modes and quantitatively reproduces the observed signal and idler responses. The NbN device exhibits a significantly larger Kerr coefficient and superior gain-bandwidth performance, highlighting the advantages of high-kinetic-inductance materials. Our results establish coupled kinetic-inductance resonators as a robust platform for broadband, high-power, and magnetically resilient quantum-limited amplification, offering a scalable route for advanced readout in superconducting qubits, spin ensembles, quantum dots, and other microwave-quantum technologies.

quant-pharXiv:2512.03362•Dec 4, 2025•0 citations

Superconducting circuits for characterizing spins and charge defects with microsecond coherence

Matteo Boselli

The detection of electric and magnetic dipole ensembles is a fundamental tool across physics, chemistry, and biology. Here, we combine low-loss microwave superconducting circuits with advanced spectroscopic techniques to probe paramagnetic samples and dielectric defects at millikelvin temperatures. In this regime, full polarization, quantum-limited amplifiers, and superconducting resonators with narrow linewidths enable a dramatic boost in sensitivity. Such capabilities even allow the study of individual dielectric defects within the circuit materials themselves. In the context of electron spin resonance (ESR), hybrid spin-superconducting platforms have already reached single-spin detection and sub-picoliter sample volumes.In our first experiment, we observed—for the first time—the emission of Hahn echoes from dielectric defects in a Josephson Traveling-Wave Parametric Amplifier, a widely used quantum-limited amplifier. These echoes, triggered at drive powers close to the amplifier's saturation threshold, can degrade device performance. Using standard pulse sequences, we characterized their dynamics, allowing to estimate the defect density in the device dielectric layers and to quantify their impact on amplifier operation.In a second experiment, we addressed the challenge of extending ESR detection to arbitrary spin ensembles, which may be highly disordered and exhibit short coherence times. While high-quality factor superconducting resonators offer exceptional detection sensitivity for spins, their long ring-down times hinder the study of rapidly dephasing spins. To overcome this, we developed a dynamically tunable resonator based on the kinetic inductance of Niobium-Titanium-Nitride (NbTiN), a superconducting alloy resilient to magnetic fields. Using fast DC current pulses, we tuned the resonator linewidth on the microsecond timescale while preserving their performance for ESR detection. We benchmarked the spectrometer by performing time-resolved spectroscopy on a 20-picoliter sample of α,γ-bisdiphenylene-β-phenylallyl at millikelvin temperatures, achieving a sensitivity only one order of magnitude below state-of-the-art experiments on highly coherent ensembles.Our results establish a versatile ESR platform operating at millikelvin temperatures, with potential applications ranging from materials characterization to the detection of unpaired electrons in single biological cells.

•Dec 11, 2025•0 citations

Inductive-detection electron-spin resonance spectroscopy with 65 spins/Hz sensitivity

S. Probst, Audrey Bienfait, Philippe Campagne-Ibarcq +10 more

We report electron spin resonance spectroscopy measurements performed at millikelvin temperatures in a custom-built spectrometer comprising a superconducting micro-resonator at 7 GHz and a Josephson parametric amplifier. Owing to the small (∼10−12λ3) magnetic resonator mode volume and to the low noise of the parametric amplifier, the spectrometer's single shot sensitivity reaches 260 ± 40 spins/echo translating into 65±10 spins/Hz for repeated acquisition.

arXiv:1708.09287•Applied Physics Letters•Nov 13, 2017•94 citations

Inductive-detection electron-spin resonance spectroscopy with 65 spins/root Hz sensitivity

Sebastian Probst, Audrey Bienfait, Philippe Campagne-Ibarcq +10 more

We report electron spin resonance spectroscopy measurements performed at millikelvin temperatures in a custom-built spectrometer comprising a superconducting micro-resonator at 7 GHz and a Josephson parametric amplifier. Owing to the small (∼10−12λ3∼10−12λ3) magnetic resonator mode volume and to the low noise of the parametric amplifier, the spectrometer's single shot sensitivity reaches 260 ± 40 spins/echo translating into 65±10 spins/Hz⎯⎯⎯⎯⎯√65±10 spins/Hz for repeated acquisition.

Applied Physics Letters•Nov 14, 2017•2 citations
The use of superconducting microresonators together with quantum-limited Josephson parametric amplifiers has enhanced the sensitivity of pulsed electron spin resonance (ESR) measurements by more than four orders of magnitude. So far, the microwave resonators and amplifiers have been designed as separate components due to the incompatibility of Josephson junction–based devices with magnetic fields. This has produced complex spectrometers and raised technical barriers toward adoption of the technique. Here, we circumvent this issue by coupling an ensemble of spins directly to a weakly nonlinear and magnetic field–resilient superconducting microwave resonator. We perform pulsed ESR measurements with a 1-pL mode volume containing 6 × 10 7 spins and amplify the resulting signals within the device. When considering only those spins that contribute to the detected signals, we find a sensitivity of 2.8 × 1 0 3 spins / Hz for a Hahn echo sequence at a temperature of 400 mK. In situ amplification is demonstrated at fields up to 254 mT, highlighting the technique’s potential for application under conventional ESR operating conditions.
The use of superconducting micro-resonators in combination with quantum-limited Josephson parametric amplifiers has in recent years lead to more than four orders of magnitude improvement in the sensitivity of pulsed Electron Spin Resonance (ESR) measurements. So far, the microwave resonators and amplifiers have been designed as separate components, largely due to the incompatibility of Josephson junction-based devices with even moderate magnetic fields. This has led to complex spectrometers that operate under strict environments, creating technical barriers for the widespread adoption of the technique. Here we circumvent this issue by inductively coupling an ensemble of spins directly to a weakly nonlinear microwave resonator, which is engineered from a magnetic field-resilient thin superconducting film. We perform pulsed ESR measurements with a 111~pL effective mode volume and amplify the resulting spin signal using the same device, ultimately achieving a sensitivity of 2.8×1032.8 \times 10^32.8×103 spins in a single-shot Hahn echo measurement at a temperature of 400 mK. We demonstrate the combined functionalities at fields as large as 254~mT, highlighting the technique's potential for application under more conventional ESR operating conditions.
Superconducting parametric amplifiers are crucial components in microwave quantum circuits for enabling quantum-limited signal readout.The best-performing such amplifiers are often based on Josephson junctions, which however are sensitive to magnetic fields.Therefore, they require magnetic shields and are not easily integratable with other quantum systems that operate within magnetic fields, such as spinensemble quantum memories.To tackle this challenge, we develop a kinetic inductance-based parametric amplifier featuring a NbN nanobridge instead of Josephson junctions, which provides the desired nonlinearity for a strong parametric gain up to 42 dB.The added noise of this nanobridge kinetic-inductance parametric amplifier (hereby referred to as NKPA) is calibrated and found to be 0.59 ± 0.03 quanta for phase-preserving amplification, approaching the quantum limit of 0.5 quanta.Most importantly, we show that such excellent noise performance is preserved in an in-plane magnetic field up to 427 mT, the maximum field available in our experiment.This magnetic-field-resilient parametric amplifier presents an opportunity towards addressing single electron-spin resonance and more efficient search for axions as well as Majorana fermions.
Parametric amplification is essential for quantum measurement, enabling the amplification of weak microwave signals with minimal added noise. While Josephson-junction-based amplifiers have become standard in superconducting quantum circuits, their magnetic sensitivity, limited saturation power, and sub-kelvin operating requirements motivate the development of alternative nonlinear platforms. Here we demonstrate a two-mode kinetic-inductance parametric amplifier based on a pair of capacitively coupled Kerr-nonlinear resonators fabricated from NbTiN and NbN thin films. The distributed Kerr nonlinearity of these materials enables nondegenerate four-wave-mixing amplification with gains approaching 40 dB, gain-bandwidth products up to 6.9 MHz, and 1-dB compression powers two to three orders of magnitude higher than those of state-of-the-art Josephson amplifiers. A coupled-mode theoretical model accurately captures the pump-induced modification of the hybridized modes and quantitatively reproduces the observed signal and idler responses. The NbN device exhibits a significantly larger Kerr coefficient and superior gain-bandwidth performance, highlighting the advantages of high-kinetic-inductance materials. Our results establish coupled kinetic-inductance resonators as a robust platform for broadband, high-power, and magnetically resilient quantum-limited amplification, offering a scalable route for advanced readout in superconducting qubits, spin ensembles, quantum dots, and other microwave-quantum technologies.
The detection of electric and magnetic dipole ensembles is a fundamental tool across physics, chemistry, and biology. Here, we combine low-loss microwave superconducting circuits with advanced spectroscopic techniques to probe paramagnetic samples and dielectric defects at millikelvin temperatures. In this regime, full polarization, quantum-limited amplifiers, and superconducting resonators with narrow linewidths enable a dramatic boost in sensitivity. Such capabilities even allow the study of individual dielectric defects within the circuit materials themselves. In the context of electron spin resonance (ESR), hybrid spin-superconducting platforms have already reached single-spin detection and sub-picoliter sample volumes.In our first experiment, we observed—for the first time—the emission of Hahn echoes from dielectric defects in a Josephson Traveling-Wave Parametric Amplifier, a widely used quantum-limited amplifier. These echoes, triggered at drive powers close to the amplifier's saturation threshold, can degrade device performance. Using standard pulse sequences, we characterized their dynamics, allowing to estimate the defect density in the device dielectric layers and to quantify their impact on amplifier operation.In a second experiment, we addressed the challenge of extending ESR detection to arbitrary spin ensembles, which may be highly disordered and exhibit short coherence times. While high-quality factor superconducting resonators offer exceptional detection sensitivity for spins, their long ring-down times hinder the study of rapidly dephasing spins. To overcome this, we developed a dynamically tunable resonator based on the kinetic inductance of Niobium-Titanium-Nitride (NbTiN), a superconducting alloy resilient to magnetic fields. Using fast DC current pulses, we tuned the resonator linewidth on the microsecond timescale while preserving their performance for ESR detection. We benchmarked the spectrometer by performing time-resolved spectroscopy on a 20-picoliter sample of α,γ-bisdiphenylene-β-phenylallyl at millikelvin temperatures, achieving a sensitivity only one order of magnitude below state-of-the-art experiments on highly coherent ensembles.Our results establish a versatile ESR platform operating at millikelvin temperatures, with potential applications ranging from materials characterization to the detection of unpaired electrons in single biological cells.
We report electron spin resonance spectroscopy measurements performed at millikelvin temperatures in a custom-built spectrometer comprising a superconducting micro-resonator at 7 GHz and a Josephson parametric amplifier. Owing to the small (∼10−12λ3∼10−12λ3) magnetic resonator mode volume and to the low noise of the parametric amplifier, the spectrometer's single shot sensitivity reaches 260 ± 40 spins/echo translating into 65±10 spins/Hz⎯⎯⎯⎯⎯√65±10 spins/Hz for repeated acquisition.