Near-Quantum-Limited Readout for the Princeton Axion Search using a sub-GHz Kinetic Inductance Traveling Wave Parametric Amplifier

Joe Wiedemann; Roman Kolevatov; Jianyang Fu; Joelle-Marie Begin; Nate Otto; Felix St-Amour; Lyman Page; Henry LeDuc; Peter Day; Saptarshi Chaudhuri

AI summary · arXiv: 2611.06761v1 · quant-ph

Near-Quantum-Limited Readout for the Princeton Axion Search using a sub-GHz Kinetic Inductance Traveling Wave Parametric Amplifier

Joe Wiedemann, Roman Kolevatov, Jianyang Fu, Joelle-Marie Begin, Nate Otto, Felix St-Amour, Lyman Page, Henry LeDuc,

and 2 more authors

Peter Day, Saptarshi Chaudhuri

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The essentials

The paper presents a 300–700 MHz kinetic-inductance traveling-wave parametric amplifier achieving over 30 dB gain and 2.5–3.5 quanta of measured system noise.

Based on the abstract only: check the details in the original paper.

Question

The work addresses the limited availability of near-quantum-limited amplifiers below 1 GHz. It evaluates whether a kinetic-inductance traveling-wave parametric amplifier can support precision sub-GHz measurements, including axion searches.

Method

The authors present and characterize a KI-TWPA operating from 300 to 700 MHz, using pump powers of a few hundred nanowatts. They measure system noise with a variable-temperature noise source and examine gain drift, compression point, noise at different amplifier operating temperatures, readout with an input circulator, and magnetic-field insensitivity.

Findings

Result The amplifier operates over 300–700 MHz, with gain exceeding 30 dB and pump powers of a few hundred nanowatts.
See the passage in the paper
We present a kinetic inductance traveling-wave parametric amplifier (KI-TWPA) operating over 300-700 MHz, with gain exceeding 30 dB and pump powers of a few hundred nanowatts.
Result The measured system noise performance is 2.5–3.5 quanta.
See the passage in the paper
The system noise performance, as measured by a variable-temperature noise source, is 2.5-3.5 quanta.
Result The authors characterize amplifier performance properties relevant to axion searches, including gain drift, compression point, operating-temperature noise, circulator readout, and magnetic-field insensitivity.
See the passage in the paper
We characterize aspects of the amplifier performance relevant to axion searches, including gain drift, compression point, amplifier noise at various operating temperatures, readout with an input circulator, and magnetic field insensitivity.
Authors’ interpretation The authors propose the device as a versatile tool for precision measurements of sub-GHz signals, with possible applications in several fields.
See the passage in the paper
This device is a versatile new tool for precision measurements of sub-GHz signals, with applications including readout of semiconductor spin qubits, superconducting detector arrays, and searches for new physics beyond the Standard Model.

Limitations

The evidence presented in the abstract is limited to characterization of a 300–700 MHz amplifier and does not report a demonstration of a specific axion search or the other proposed applications.

Why it matters

The authors argue that the amplifier extends near-quantum-limited parametric-amplifier technology into the sub-GHz range. They identify potential uses in axion searches and other precision measurements.

Written by AI from the paper. Passages are checked word for word against the text we analysed; the rest may contain errors.

AI-generated keywords: KI-TWPA sub-GHz amplification quantum-limited measurement axion search system noise

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Comprehensive Summary
Layman's Summary
Blog article
Original abstract

The paper addresses a measurement challenge in the sub-gigahertz range. Parametric amplifiers can enable measurements near the quantum limit, but their development below 1 GHz has been more limited. The authors present a kinetic inductance traveling-wave parametric amplifier (KI-TWPA) designed for precision measurements in this range, including the Princeton Axion Search. The device operates from 300 to 700 MHz. According to the abstract, it achieves gain exceeding 30 dB with pump power of a few hundred nanowatts. The authors assess its noise performance using a variable-temperature noise source and report system noise of 2.5–3.5 quanta. These results characterize the amplifier system; they do not establish a single noise value for all operating conditions. The authors also characterize several factors relevant to axion-search readout: gain drift, compression point, amplifier noise at different operating temperatures, operation with an input circulator, and sensitivity to magnetic fields. The abstract does not provide the measured values or detailed test conditions for these characterizations. It therefore indicates that the amplifier was evaluated for practical integration into an axion-search measurement chain, but it does not support a more detailed account of those results. The authors present the KI-TWPA as a versatile tool for sub-GHz precision measurements. Potential applications include readout of semiconductor spin qubits and superconducting detector arrays, as well as searches for physics beyond the Standard Model. Its reported frequency coverage, high gain, low pump-power requirement, and measured system noise make it relevant to applications that require amplification of weak signals with limited added noise. This summary is based only on the title and abstract; the supplied source indicates that the license does not permit access to the full text. As a result, it does not include details of the amplifier’s design and fabrication, experimental setup, measurement uncertainties, precise operating conditions, or performance-characterization results beyond the reported frequency range, gain, pump power, and noise figures. The abstract also does not establish how the device performs in a complete axion search or quantify any improvement in search sensitivity. The reported results suggest that the KI-TWPA is a promising sub-GHz measurement amplifier, but assessing these details requires access to the full paper.

A Low-Noise Amplifier for the Sub-Gigahertz Frontier

Weak signals are difficult to measure. In the sub-gigahertz range—below 1 GHz—even a small amount of noise added by a readout system can obscure the signal researchers hope to detect. Parametric amplifiers can bring measurements close to the quantum limit, but their development at these lower frequencies has been more limited.

In “Near-Quantum-Limited Readout for the Princeton Axion Search using a sub-GHz Kinetic Inductance Traveling Wave Parametric Amplifier,” Joe Wiedemann, Roman Kolevatov, Jianyang Fu, Joelle-Marie Begin, Nate Otto, Felix St-Amour et al. present a kinetic inductance traveling-wave parametric amplifier, or KI-TWPA, designed to address this challenge. The work focuses on amplification for precision measurements, including readout for the Princeton Axion Search.

Amplification from 300 to 700 MHz

The amplifier operates across a frequency range of 300 to 700 MHz. The authors report gain exceeding 30 dB while using pump power of a few hundred nanowatts. High gain can help bring faint signals to a level that downstream electronics can handle, while modest pump-power requirements are relevant for practical measurement systems.

To assess noise performance, the researchers used a variable-temperature noise source. They report system noise of 2.5–3.5 quanta. This is a measured range for the amplifier system, not a single noise figure that applies under every operating condition. Noise performance can depend on how the device and its surrounding measurement chain are configured and operated.

Testing for Practical Readout

Performance in a laboratory measurement chain involves more than gain and noise. The authors also characterize factors that matter for integrating the KI-TWPA into an axion-search readout system, including gain drift, compression point, amplifier noise at different operating temperatures, operation with an input circulator, and sensitivity to magnetic fields.

The abstract does not provide the measured values or detailed conditions for these tests. It therefore supports the conclusion that the amplifier was evaluated with practical integration in mind, but not a more specific account of how it performed in each characterization. Those details would be needed to compare operating configurations or assess the implications for a particular experiment.

Potential Uses Beyond Axion Searches

The authors describe the KI-TWPA as a versatile tool for sub-gigahertz precision measurements. Its reported frequency coverage, gain, low pump-power requirement, and system-noise results make it relevant to experiments that need to amplify weak signals while adding limited noise.

Potential applications named in the paper include:

Readout of semiconductor spin qubits
Readout of superconducting detector arrays
Searches for physics beyond the Standard Model

These are areas where sensitive measurements can be important. However, the abstract does not establish how the amplifier performs in a complete axion search or quantify an improvement in search sensitivity. The reported device characteristics should not be taken as evidence of a particular experimental outcome.

What the Available Summary Can—and Cannot—Show

This overview is based only on the paper’s title and abstract; the supplied source indicates that its license does not permit access to the full text. As a result, it cannot describe the amplifier’s design and fabrication, the complete experimental setup, measurement uncertainties, or precise operating conditions. It also cannot provide the detailed results of the practical performance tests.

The reported findings nevertheless point to a promising approach for sub-gigahertz readout: a KI-TWPA spanning 300–700 MHz, delivering more than 30 dB of gain with a few hundred nanowatts of pump power, and showing system noise of 2.5–3.5 quanta in the reported measurements. Determining how those characteristics translate into a full axion-search measurement—or into other applications—requires the additional results and context available in the paper itself.

Created on 10 Nov. 2026

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Weekly letter Presented in "Quantum physics this week" of 9 November 2026. Quantum physics this week: Protecting fragile states, exposing fragile advantages

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Near-Quantum-Limited Readout for the Princeton Axion Search using a sub-GHz Kinetic Inductance Traveling Wave Parametric Amplifier

The essentials

Question

Method

Findings

Limitations

Why it matters

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Definitions

A Low-Noise Amplifier for the Sub-Gigahertz Frontier

Amplification from 300 to 700 MHz

Testing for Practical Readout

Potential Uses Beyond Axion Searches

What the Available Summary Can—and Cannot—Show

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