Superconducting Technologies for Dark Matter

11 May 2026, 12:00 → 13 May 2026, 14:00 Europe/Rome

Roma

Lindley Anne Winslow (MIT), Marco Vignati (Istituto Nazionale di Fisica Nucleare)

Workshop on the search for wave- and particle-like Dark Matter using superconducting detectors, covering theoretical motivations and experimental approaches, including beyond–standard quantum limit readout techniques and microwave multiplexing of sensors.

Registration deadline: April 12, 2026.

Talks are by invitation only. Poster abstracts can be submitted through the dedicated form.

Abstract deadline: March 29, 2026.

The event is sponsored by the Physics Department of Sapienza University - Dipartimento di Eccellenza (Excellence Department project from the Ministry of Research and Education).

Monday 11 May

12:00 → 13:30 Welcome Lunch and Registration

13:30 → 14:00 Welcome

13:30 Director's Welcome

Speaker: Daniele Del Re (Istituto Nazionale di Fisica Nucleare)

13:35 Welcome

Speakers: Lindley Anne Winslow (MIT), Marco Vignati (Istituto Nazionale di Fisica Nucleare)

14:00 → 14:50 Overview: Theory

Convener: Marco Vignati (Istituto Nazionale di Fisica Nucleare)

14:00 Axions in 2026: Theory and Astrophysical/Cosmological Bounds

In this talk I will review the basic theory for axions and axion-like particles, and then review some of the most recent developments in astrophysics and cosmology.

Speaker: Andrea Caputo

14:25 From quantum sensors to demon materials: New directions for light dark matter

Speaker: Yonit Hochberg

14:50 → 16:30 Upcoming WIMP-like Experiments

Convener: Gianluca Cavoto (Istituto Nazionale di Fisica Nucleare)

14:50 BULLKID-DM: searching for light WIMPs with monolithic arrays of detectors

BULLKID-DM is a new experiment designed to search for low-mass WIMP-like dark matter particles (1 GeV/c or below) with nucleon cross-sections below 10 cm. The device consists of an 800 g array of over 2000 silicon dice, each acting as a particle absorber instrumented with multiplexed Kinetic Inductance Detectors (KIDs). Background rejection is achieved through a fully active structure, enabling fiducialization and anti-coincidence techniques.

A 20 g prototype, consisting of 60 voxels 5.4x5.4x5 mm in size diced from a 3'' silicon wafer, demonstrated the feasibility of this approach. Following its success, we present the first operation, in a surface laboratory equipped with a lead and copper radiation shield, of a 60 g demonstrator with 180 dice. This demonstrator setup acts as a proof of concept for the final 800 g array. The recorded backgrounds are compared to Geant4 simulations performed by the collaboration.

We also discuss ongoing R&D activities, including low-radioactivity detector mounting, a cryogenic scintillating veto readout with KIDs, in situ calibration techniques, and detector upgrades such as KIDs with dedicated phonon-collecting structures and germanium substrates for multi-target capabilities.

Finally, we outline the deployment plan of the setup at the Gran Sasso underground laboratory (LNGS). The demonstrator will be installed at LNGS by late 2026; following successful validation, the full experiment is expected to be commissioned in 2027.

Speaker: Daniele Delicato (Istituto Nazionale di Fisica Nucleare)

15:15 Ge and Si Cryogenic Calorimeters for the TESSERACT Experiment

The TESSERACT (Transition Edge Sensors with Sub-eV Resolution And Cryogenic Targets) experiment is an international collaboration between the USA, France, and Switzerland that aims to search for light dark matter over a wide range of masses (from the proton mass down to a few meV) at the Modane Underground Laboratory (LSM). To achieve this goal, it will utilize different cryogenic detector technologies made from various target materials: superfluid helium, polar crystals, and Ge or Si bolometers. For Ge and Si, two different technologies are being developed, both based on aluminum electrodes evaporated onto the surface of the crystals with a bias voltage applied to them. In one case, this bias is low (<10 V), and the detector is equipped with a phonon sensor and a charge readout. This dual-measurement approach allows for discrimination between nuclear recoil-induced events and electronic recoil events, providing a way to reject background events. In the second case, the bias voltage is high (>50 V), focusing on the detection of Neganov-Trofimov-Luke phonons using a point-contact NbSi TES, which boosts the signal to achieve single electron/hole pair sensitivity.
In this talk, I will present the most recent advancements in both of these technologies and present the prospects for their integration into the TESSERACT experiment.

Speaker: Antoine Armatol

15:40 Through the looking glass: enabling broadband DM sensitivity enhancement with amorphous solids

Previously proposed dark matter absorption searches using crystalline targets face a fundamental limitation: momentum conservation in a perfect crystal restricts absorption to occur only when the dark matter mass is resonant with one of a small number of optical phonon frequencies. For a dark matter mass hypothesis that doesn't coincide with these narrow resonances, absorption must proceed through heavily suppressed multi-phonon processes, leaving the detector essentially blind to these cases. Amorphous materials, which lack long-range translational order, circumvent this constraint entirely. The continuum spectrum of vibrational modes of amorphous materials means that an absorption mode is always available for a wide range of dark matter masses, yielding a response that is intrinsically broadband. As a result, amorphous targets such as silicon dioxide or silicon nitride can achieve absorption rates one to two orders of magnitude larger than their crystalline counterparts across much of the 50–200 meV$/c^2$ mass range, without the need to build and operate many detectors from different materials, each resonant at a different frequency, to achieve comparable coverage. This talk highlights the theoretical foundation underlying broadband enhancement in dark matter absorption sensitivity with amorphous solids and the proposed detector design for a low-mass dark matter direct detection experimental program.

Speaker: Brooke Russell

16:05 Quantum Sensors for Dark Matter Detection

Low-mass dark matter is now a central focus in direct-detection research. Decades without a WIMP signal have driven the community to broaden theoretical models and explore new mass ranges. The next frontier is detecting dark-matter interactions at eV scales and below. The SuperCDMS-derived HVeV R&D devices have shown resolution below 1 eV, and advances in quantum sensing have opened pathways to meV thresholds using qubit-based parity detection and even µeV sensitivity through quantum acoustic techniques. I will discuss all these new developments and present an idea for a new experiment that combines these technologies to obtain sensitivity to energy recoils over a huge dynamic range from µeV to keV.

Speaker: Enectali Figueroa-Feliciano

16:30 → 17:00 Break

17:00 → 18:30 TES Based Neutrino and Dark Matter

Convener: Claudia Tomei (Istituto Nazionale di Fisica Nucleare)

17:00 Probing Sub-GeV Dark Matter with TES: The CRESST Experiment

The Cryogenic Rare Event Search with Superconducting Thermometers (CRESST), located at the Laboratori Nazionali del Gran Sasso (INFN, Italy), targets the direct detection of sub-GeV dark matter (DM) via nuclear recoils in cryogenic CaWO$_4$ detectors instrumented with tungsten Transition Edge Sensors (W-TES). Operating at millikelvin temperatures, these detectors combine phonon and light readout to achieve nuclear recoil energy thresholds at the $\mathcal{O}$(10–30 eV) level, enabling world-leading sensitivity to DM particles with masses below 1.7 GeV/$c^2$.

At the lowest energies, CRESST observes a steeply rising population of events below 200 eV, referred to as the Low Energy Excess (LEE), which currently sets the dominant limitation on sensitivity. The recently developed DoubleTES approach, based on the coincident readout of two TES sensors on a single absorber, provides, for the first time, a handle to identify and possibly mitigate this excess.

Combined with targeted optimisations of the TES design and operating conditions, these developments lead to improved signal-to-noise performance and enhanced background rejection. We present the latest results on LEE mitigation together with the most recent constraints on light dark matter interactions.

Speaker: Paolo Gorla (Istituto Nazionale di Fisica Nucleare)

17:20 NUCLEUS - Low threshold cryogenic detectors for coherent neutrino scattering

Speaker: Raimund Strauss (TUM)

17:40 Transition-Edge Sensor Readout via Nonlinear Superconducting Microresonators in the HOLMES Experiment for Neutrino Mass Determination

The absolute value of the neutrino mass 𝑚𝜈remains one of the key missing pieces in the Standard Model. Its value plays a fundamental role in shaping the formation of large-scale structures in the Universe. The only model-independent method to determine 𝑚𝜈relies on direct kinematic measurements of the electrons emitted in beta decay processes. Current experimental approaches fall into two categories: spectrometers and calorimeters. Spectrometer-based experiments have set the most stringent limits so far - most notably KATRIN, which has reached a sensitivity of 0.45 eV and is progressing toward its design goal of 0.2 eV. However, spectrometers have reached practical limits in size and complexity, and the external-source configuration inherently introduces systematic effects
such as energy-loss corrections.

Calorimetric experiments avoid these issues by embedding the source within the active volume of low-temperature detectors, thereby measuring the full energy released in the decay except the neutrino’s share. Their main challenge is balancing the large statistics required for competitive sensitivity with the need to suppress pile-up, which can otherwise dominate the background in the region of interest. Achieving this balance demands distributing the total activity among a large array of detectors and equipping them with a highly efficient multiplexed readout system.

HOLMES is a calorimetric experiment designed to measure the electron capture decay of 163Ho for neutrino mass determination. After successfully demonstrating the readout of transition-edge sensors (TESs) using SQUID-based microwave multiplexing (μmux), HOLMES is now targeting a more scalable and bandwidth-efficient solution for future large-scale deployments. This new approach is based on kinetic inductance current sensors (KICS), a novel technique exploiting nonlinear superconducting microresonators to achieve high multiplexing factors.

In parallel with the development of KICS, HOLMES is transitioning from 100 mK TESs to new 40 mK TESs designed to mitigate the additional heat capacity introduced by the implanted 163Ho atoms.

In this contribution, after outlining the HOLMES experiment along with its current status and challenges, I will present recent progress on the development of the KICS-based readout scheme and the new low-𝑇𝑐 TES detectors.

Speaker: Matteo Borghesi (Istituto Nazionale di Fisica Nucleare)

18:05 Development of TES sensors for CUPID

CUPID — CUORE Upgrade with Particle Identification — is the ton-scale neutrinoless double beta decay (NLDBD) experiment at LNGS. CUPID will be mounted in the CUORE cryostat, leveraging the existing cryogenic infrastructure and a decade of experience operating the largest bolometer array in existence. CUPID will deploy 1600 Li2MoO4 scintillating bolometers with the dual heat-light readout to achieve a low-background search for NLDBD in the inverted ordering region of the neutrino mass parameter space. An even larger, possibly distributed bolometric array, CUPID-1T with over a metric ton of Mo-100, would be the next-generation experiment with sensitivity in the normal ordering region of neutrino masses. We will discuss the technological developments for CUPID, including the development of superconducting TES sensors with multiplexed readout, and novel detector concepts that could allow for a background-free searches for NLDBD.

Speaker: Yury Kolomensky

Tuesday 12 May

09:00 → 11:05 Wave Dark Matter

Convener: Lindley Anne Winslow (MIT)

09:00 Beyond multi-cavity searches with ADMX-VERA: a large volume detection scheme for high frequencies

The Axion Dark Matter eXperiment (ADMX) first achieved sensitivity to the DFSZ axion using a cavity haloscope coupled to a microstrip SQUID amplifier. ADMX has continued to scan upwards in frequency using the single-cavity approach. The collaboration intends to switch to a multi-cavity setup for future runs; however, the multi-cavity approach is not sustainable long term. I will present an alternative approach that uses a large volume resonator whose axion-coupled mode is determined by a narrow dimension while other dimensions are scaled to recover the volume typically lost at high frequencies. I will discuss the implementation of these resonators in a staged approach to achieve sensitivity to the DFSZ axion between 4 and 20 GHz through the ADMX-VERA program.

Speaker: Chelsea Bartram

09:25 Searches for axion and dark photon dark matter with MADMAX

The MAgnetized Disk and Mirror Axion eXperiment (MADMAX) collaboration is aiming to detect dark matter axions from the galactic halo by resonant conversion to photons in a strong magnetic field. It uses the novel dielectric haloscope concept based on a stack of dielectric disks in front of a mirror, called booster, to enhance the potential signal from axion-photon conversion over a significant mass range. In its final version, MADMAX aims to scan the uncharted QCD axion mass range around 100 µeV, favoured by post-inflationary theories.
Several small-scale prototype systems have been tested, allowing to validate the dielectric haloscope concept and perform competitive axion and dark photon dark matter searches. In this presentation the current status of the experiment and its prototypes, including the results achieved so far, the ongoing research & development and the future plans will be presented.

Speaker: Béla Majorovits

09:50 An idea for an ultra-broadband axion dark matter experiment

Speaker: Angelo Esposito (Istituto Nazionale di Fisica Nucleare)

10:15 BREAD: Broadband Axion Detection with Superconducting Sensors from Microwaves to the Infrared

The search for axion dark matter in the microwave regime demands detector technologies capable of resolving extraordinarily weak electromagnetic signals with near- or sub- quantum-limited sensitivity. The Broadband Reflector Experiment for Axion Detection (BREAD) aims to address this challenge by combining large-aperture electromagnetic collection concepts with state-of-the-art superconducting sensor technologies.
In contrast to resonant cavity experiments, BREAD explores a broadband detection strategy, enabling sensitivity over a wide frequency range without the need for mechanical tuning. This approach places stringent requirements on the detector: low noise, large bandwidth, and efficient coupling.

We present our current progress toward implementing superconducting detection schemes tailored for this purpose, specifically by integrating a Kinetic Inductance Traveling Wave Parametric Amplifier with a BREAD protoype searching for dark matter between 10-15 GHz. We also present other BREAD prototypes optimized for different frequency ranges from microwaves to the infrared, and discuss how different superconducting sensors including bolometers and photon counters could enable them to reach the DFSZ axion sensitivity.

Speaker: Juan Maldonado

10:40 Search for Postinflationary QCD Axions with a Quantum-Limited Tunable Microwave Receiver

A search for cosmological axions has been performed by scanning a frequency region of 38 MHz centered at about 10.2 GHz, corresponding to an axion mass ma ≃ 42 μeV. The QUAX experimental apparatus, a haloscope comprised of a 1-liter volume tunable cavity immersed in an 8 T magnetic field and a quantum-limited detection chain, set limits on the axion-photon coupling at the 10−14 GeV−1 level. As no signal candidate has been observed, viable hadronic axion models are ruled out in a currently preferred postinflationary region ma > 40 μeV. In this talk I will mainly focus on the description of the experimental apparatus, with a short final illustration of the data analysis and results.

Speaker: Giuseppe Ruoso (Istituto Nazionale di Fisica Nucleare)

Abstract Roma 2026.pdf

11:05 → 11:35 Break

11:35 → 13:15 Session

Convener: Francesco Pandolfi (INFN Rome)

11:35 The Tesseract Sub-GeV Dark Matter Experiment

The TESSERACT project will search for sub-GeV dark matter via multiple complementary advanced, ultra-sensitive phonon detectors, sensitive to nuclear-type, electron-type, and dark photon-type DM interactions, using three detector technologies: superfluid helium, polar crystals (GaAs and sapphire), and germanium/silicon bolometers. Those detectors will share Transition Edge Sensors (TES) for phonon readout and experimental settings. Besides maximising sensitivity, this multi-target approach also allows us to identify and discriminate against novel instrumental and physical backgrounds. The experiment is presently in a period of targeted R&D, with the first physics results based on demonstrator setups to be expected this year and all detectors working. Full integration of the TESSERACT setup at the Modane Underground Laboratory (LSM) is planned for 2028. We will present the status of the experiments and sensors with focus on the superfluid helium and polar crystals, expected sensitivities, and possible ways to achieve sub-MeV dark matter mass sensitivity.

Speaker: Björn Penning

12:00 Search for dark matter with SNSPDs: the QROCODILE experiment

The QROCODILE (Quantum Resolution-Optimized Cryogenic Observatory for Dark matter Incident at Low Energy) experiment uses superconducting nanowire single-photon detectors (SNSPDs) to search for scattering and absorption of dark matter (DM) candidates with masses as low as 30 keV. We conducted a first measurement at the University of Zurich with a WSi SNSPD placed on a Si/SiO2 substrate, and we set new world-leading constraints for DM-electron scattering, DM-nucleon scattering and electronic absorption of dark photons. In this presentation I will discuss the working principle, recent results and future plans of QROCODILE.

Speaker: Chiara Capelli (University of Zurich)

12:25 Superconducting Nanostrips for Dark-Matter Detection

Superconducting nanostrips are well-established as a device technology for quantum sensing, having found use in fields as diverse as deep-space communication, LIDAR, and quantum cryptography. However, these applications generally take advantage of the exceptional timing resolution and fast reset time of these devices. In contrast, for dark matter detection, the exceptionally low dark-count rate of superconducting-nanostrip-based detectors is one of the primary motivating factors. These devices have demonstrated dark count rates in the few-counts per week range (≲ 10 μcps) while exhibiting detection efficiency in the ≳ 10% range for photon energies of interest to detector approaches like LAMPOST [1], QROCODILE [2]. This unique combination of low dark count rate and high efficiency (with the potential for efficient detection at photon energies ≲ 100 meV) makes these detectors attractive for future dark-matter detection. One planned experiment is DPHASE [3], in which a dielectric powder is to be used as a dark-matter absorber, with the aim of generating optical and infrared photons in the powder and then detecting them with a superconducting-nanostrip-based detector at the detector surface. In this presentation, we will discuss nanostrip detectors, the origin of the unique properties that make them robust against dark-counts, and the possibilities for scaling them to dimensions and scales that would be of particular interest to various dark-matter-detector approaches.

[1] Chiles et al., Phys. Rev. Lett. 128, 231802 (2022)

[2] Baudis et al., Phys. Rev. Lett. 135, 081002 (2025)

[3] Koppell et al., Phys. Rev. D, Accepted, 2026

Speaker: Karl Berggren

12:50 Passive Superconducting Thermoelectric Detectors as Broadband Quantum Sensors: A New Window on Dark Matter

Detecting extremely weak electromagnetic signals is a central challenge in quantum technologies and fundamental physics, especially in searches for dark matter candidates such as axions. We present a new detection scheme [1] based on passive superconducting thermoelectric single-photon detectors (TEDs), which use bipolar thermoelectric effects in tunnel junctions between superconductors with different energy gaps [2,3]. Unlike
conventional cryogenic detectors, TEDs operate without external bias and convert the absorption of a single photon directly into a measurable thermovoltage. This passivity greatly reduces electrical noise and thermal load, enabling scalable architectures and improved sensitivity at ultralow temperatures. The detector offers a broadband response from tens of gigahertz up to the petahertz regime, with an operational bandwidth over more than four orders of magnitude and signal-to-noise ratios ~15 even at gigahertz frequencies. A key feature is its quasi-digital response: the output voltage is nearly constant over a wide frequency range, while spectroscopic information is encoded in the time profile of the thermoelectric signal. This combination of broadband sensitivity, low noise, and intrinsic energy discrimination makes TEDs well-suited for detecting extremely faint photon fluxes. They are particularly relevant for dark matter searches, as their single-photon resolution in the microwave-to-terahertz range matches the requirements of axion and axion-like particle experiments, where photon-conversion events are expected to be rare and weak. Their passive operation, scalability, and compatibility with existing cryogenic infrastructure position superconducting thermoelectric detectors as promising tools for next-generation dark matter experiments and as a versatile, high-performance sensing platform at the interface of quantum metrology and astroparticle physics.

References
[1] A highly-sensitive broadband superconducting thermoelectric single-photon detector, F. Paolucci, G. Germanese, A. Braggio, and F. Giazotto, Appl. Phys. Lett. 122, 173503 (2023).
[2] Bipolar Thermoelectric Josephson Engine,G. Germanese, F. Paolucci, G. Marchegiani, A. Braggio, and F. Giazotto, Nat. Nanotechnol. 17, 1084 (2022).
[3] Phase-control of bipolar thermoelectricity in Josephson tunnel junctions, G. Germanese, F. Paolucci, G. Marchegiani, A. Braggio, and F. Giazotto, Phys. Rev. Applied 19, 014074 (2023).

Speaker: Francesco Giazotto (NEST, Istituto Nanoscienze - CNR & Scuola Normale Superiore)

13:15 → 14:30 Lunch

14:30 → 16:10 Axion Sensing 1

Convener: Claudio Gatti (Istituto Nazionale di Fisica Nucleare)

14:30 Remote quantum non-demolition measurement of a microwave cavity field

The advent of quantum-enhanced sensing methods in axion dark matter searches holds the promise of surpassing the quantum-limited scan rate by an order of magnitude or more. Superconducting circuits enable the generation of squeezed states in axion haloscopes and the direct detection of microwave photons. But the strong magnetic fields required in axion haloscopes complicate the use of superconducting circuits, necessitating their placement tens of centimeters from the cavity and connection via a lossy transmission line. We show analytically and demonstrate experimentally that a cavity can inherit the quantum amplification properties of a remote superconducting circuit through lossy transmission-line modes, without incurring the associated loss. The superconducting circuit can be operated in three distinct modes: as a noiseless mixer that converts cavity photons to a different frequency, as a phase-preserving quantum-limited amplifier, and as a quantum non-demolition (QND) amplifier of a single quadrature. We demonstrate that the QND amplifier yields a tenfold increase in scan rate relative to the conventional haloscope strategy employing a matched quantum-limited amplifier at the cavity output, which we benchmark using the noiseless mixer operation. Beyond providing an in-situ quantum-limited benchmark, a noiseless mixer could be combined with a fixed-frequency photon counter to enable direct photon detection in a frequency-tunable haloscope cavity.

Speaker: Konrad Lehnert

14:55 Low-Mass Axion Detection Geometries and Quantum Limits

Speaker: Kent Irwin

15:20 Unlocking the secrets of the universe by graphene-based single-photon detector

The nature of dark matter remains one of the greatest mysteries in physics. While traditional axion searches rely on resonator-based experiments with narrow bandwidths, the next frontier in detection demands a broader, more efficient approach. Our research on the graphene-based single-photon bolometer aims to revolutionize this search by developing an unprecedented single-photon detector with extreme sensitivity across a wide frequency range (100 GHz–10 THz). By leveraging the unique quantum properties of graphene-based sensors, we plan to provide high quantum efficiency, ultra-low dark counts, and a broadband response, accelerating axion searches by orders of magnitude. Unlike conventional resonant cavity techniques that require extensive scanning, our calorimetric detector will capture axion-induced photons efficiently in real time, potentially compressing decades of search time into mere days. In this talk, I will introduce the principles behind WIXARD’s quantum sensing technology, share our latest experimental results, and discuss how this novel approach will push the boundaries of fundamental physics. By enabling precision detection in the millimeter to far-infrared regime, WIXARD is poised to be a game-changer—not just for dark matter searches, but for a wide range of quantum sensing applications.

References:
1. B. Huang, et. al., “Calorimetric single-photon detector using graphene,” Nature Communication (2026).
2. E. D. Walsh, et. al., “Josephson junction infrared single-photon detector,” Science 372, 409 (2021).
3. G.-H. Lee, et. al., “Graphene-based Josephson junction microwave bolometer,” Nature 586, 42 (2020).

Speaker: Kin Chung Fong

15:45 Photon counting in axion haloscopes

The interaction with the electromagnetic field is the most exploited in haloscopes, detectors where axions are resonantly converted into photons in the presence of an intense magnetic field. Some models also predict interaction with electron spin, which can be probed using a ferrimagnetic haloscope. In this detector, hypothetical particles are converted into magnons in a material with specific magnetic properties. These excitations are observable through a transduction process occurring in the strong coupling regime between the magnetization mode and the photon mode of a microwave cavity, where magnetic excitations give rise to photons in the photon mode.
In my contribution, I will discuss how the use of quantum sensors allows for significant improvement in the sensitivity of these experiments with both empty cavities and cavities hosting magnetic materials.
I will start by briefly reporting the results of a recent pathfinder experiment, where a transmon-based single microwave photon detector (SMPD), developed within the Quantronics group in Saclay, was used to read an axion-photon haloscope under 2T in a narrow frequency range.
The discussion will then expand on the use of this sensor in experiments with hybrid systems over broader bands, describing the ferrimagnetic haloscope that we have developed to match the frequency of the next-generation sensor.

Co-authors:
Danho Ahn, Patrice Bertet, Giovanni Carugno, Raffaele Di Vora, Maiello Dora, Emmanuel Flurin, Alexandre May, Antonello Ortolan, Giuseppe Ruoso, Giosue' Sardo Infirri

Speaker: Caterina Braggio (Istituto Nazionale di Fisica Nucleare)

16:10 → 17:20 Break

16:10 → 17:20 Poster Session

16:15 A machine learning approach for optimizing quantum sensing protocols on superconducting qubits

Quantum sensing protocols based on superconducting qubits are emerging as promising tools for applications ranging from fundamental physics to the search for axion dark matter with haloscopes. Achieving high-sensitivity photon detection with low dark-count rates is crucial for resolving single-photon wavepackets and weak coherent fields. A promising platform employs networks of superconducting qubits dispersively coupled to a microwave resonator. However, accurately modeling and optimizing these systems under realistic noise conditions requires numerical methods beyond tractable analytical approaches.
We present QSOpt (Quantum Sensing Optimization), a simulation and optimization framework designed for networks of superconducting qubits coupled to a resonator. The key innovation is the application of gradient-based optimization techniques to photon detection protocols in regimes where noise and system complexity preclude analytical solutions. QSOpt integrates the QuTiP quantum simulation library with a JAX backend, enabling efficient automatic differentiation and scalable optimization.
The framework supports joint optimization of hardware parameters, such as dispersive shifts and cavity couplings, and quantum circuits for state preparation. The latter is implemented within a quantum machine learning paradigm, allowing exploration of both separable and entangled multi-qubit states. This approach enhances detection performance under realistic noise and enables the discovery of previously unexplored multi-qubit sensing protocols.

Speaker: Nathan Campioni (Sapienza Università di Roma)

16:15 CRAB: Precision Measurements of Sub-keV Nuclear Recoils in Cryogenic Detectors

The CRAB (Calibrated nuclear Recoils for Accurate Bolometry) experiment uses neutron capture to study the sub-keV nuclear recoil response of cryogenic detectors with high precision, a key ingredient for the interpretation of CEνNS measurements and dark-matter searches.

After the successful validation of the method, demonstrated by the detection of a 112 eV recoil peak in a CaWO₄ cryogenic detector exposed to a commercial neutron source, an innovative experimental setup has been installed and commissioned at the TRIGA Mark-II reactor at the Atominstitut in Vienna, where the cryostat is combined with a low-intensity thermal neutron beam and gamma detectors.

In this poster, I will present new results obtained with CaWO₄ and Al₂O₃ detectors, demonstrating that the nuclear recoil energy scale can be determined with better than percent-level accuracy in the few-hundred-eV range. I will also outline prospects for a precision comparison with the electronic recoil response, as well as the extension of this program to additional target materials such as Ge and Si.

Speaker: Elisabetta Bossio (CEA Paris-Saclay)

16:15 Impact of Ionizing Radiation on Noise and Correlated Errors in Superconducting Qubit Arrays

Interactions of radioactive radiations with superconducting qubit chips generate dense cascades of electron-hole pairs, whose recombination produces high-energy phonons. These phonons can propagate across the substrate and break Cooper pairs, creating quasiparticles that degrade qubit coherence and induce excess noise and correlated errors across multiple qubits. In this work, we quantitatively investigate noise events and correlated error mechanisms arising from a Radium-224 source placed near to a multi-qubit superconducting chip. We introduce a robust data selection methodology to isolate radiation-induced events from background noise originating from other sources. The rate of radiations induced events are found to scale with source activity and follows an exponential decay consistent with the radioactive decay of the source. We further present the performance of superconducting qubits operated as phonon-mediated detectors, reporting results obtained with a single qubit as well as with configurations combining up to three qubits. Finally, we provide a quantitative characterization of multi-qubit correlated error events and discuss the prospects of this approach for radiation detection applications.

Speaker: Raja Yasir Mehmood Khan (Gran Sasso Science Institute, L'Aquila, Italy)

16:15 Probing the dark matter - electron scattering detection potential with BULLKID-DM

Speaker: Camilla Bonomo (Istituto Nazionale di Fisica Nucleare)

16:15 Strongly tunable YIG gyromagnetic modes for dark matter search

We propose a paradigm for quantum enhanced axion dark matter search, which does not rely on power measurements. We propose to measure directly the axion amplitude and phase in an interferometric protocol at the quantum limit, using a non-linear cavity. In addition, we introduce gyromagnetic modes as wide mass range transducers for axion signals compatible with standard haloscope designs. We expect this scheme to offer an improvement of at least 4 orders of magnitude in figure of merit and at least 2 orders of magnitude in mass window with respect to standard haloscopes. Owing to its generality, our proposed protocol has the potential to speed up axion search but also the search for dark photons or other cosmological objects, such as galactic masers.

Speaker: Jeanne Bally (Laboratoire de Physique de l'Ecole Normale Supérieure)

16:15 The BULLKID-DM Demonstrator

Speakers: Davide Quaranta (Istituto Nazionale di Fisica Nucleare), Matteo Folcarelli (Istituto Nazionale di Fisica Nucleare)

16:15 Towards High-Resolution Spectroscopy of Low-Energy Electrons with Transition- Edge Sensors

Transition-edge sensors (TESs) are thin superconducting films operated close to their critical temperature, and have been employed as micro-calorimeters with excellent intrinsic energy resolution in the detection of single photons. Recent works have explored their potential for the detection of single electrons. This can be a key point in rare-event
searches, ranging from neutrino experiments to dark matter investigation. The experimental setup at INRiM (Istituto Nazionale di Ricerca Metrologica), in Italy, uses a cold electron source based on field emission from vertically-aligned carbon nanotubes, coupled with bilayer gold/titanium TES devices with a critical temperature between 80 and 90 mK. It has already demonstrated the detection of single electrons in the 100 eV energy range, with an energy resolution compatible with that of photons of the same energy. In our latest results, we have improved on the experimental conditions so as to drastically reduce partially-absorbed events, and achieving a FWHM about 20 times better than in previous measurements. This represents a major milestone in the development of high- precision spectroscopy for low-energy electrons with TES devices, which can become an enabling technology also for dark matter research.

Speaker: Benedetta Corcione (Istituto Nazionale di Fisica Nucleare)

16:35 Broad frequency tuning of a Nb₃Sn superconducting microwave cavity for dark matter searches

We demonstrate a broadband frequency tuning mechanism applied to a superconducting Nb₃Sn-coated microwave cavity for wave-like dark matter (DM) searches. The cavity consists of two halves: one fixed and one mounted on a sliding cart, enabling a controllable axial gap of up to 6 mm. This "tuning-by-opening" approach changes the effective radius of the cavity and shifts the resonance from 9 GHz down to 7.8 GHz, a much broader range than typical systems. Finite-element simulations indicate that radiative losses remain negligible, with intrinsic quality factors on the order of 10⁷ preserved for apertures up to several millimeters. Experimental measurements using both discrete spacers and the continuous translation confirm Q₀ values exceeding the DM quality factor of 10⁶ across the full tuning range. The combination of high Q and wide, continuous tuning makes this technique a promising tool for next-generation haloscope searches, including implementations compatible with high magnetic fields required for axion searches.

Speaker: Dora Maiello

16:35 Development of TES-Based Cryogenic Detectors for Rare-Event Searches

Transition edge sensors (TES) are recognized as a key technology for cryogenic detectors requiring high sensitivity, fast response, and scalability to large numbers of channels. Within the framework of the CUPID (CUORE Upgrade with Particle IDentification) experiment, which aims to search for neutrinoless double beta decay, recent advances in TES technologies are presented, including developments of both bilayer and tungsten-based sensors. Fabrication methods, optimization strategies, and detector performance at millikelvin temperatures are reviewed, with emphasis on energy resolution, signal-to-noise ratio, and timing response relevant for particle identification and pile-up rejection. Particular attention is given to scalable readout architectures, where frequency-domain multiplexing (fMUX) is used to enable the simultaneous readout of multiple channels while reducing wiring complexity and cryogenic heat load. Results on multiplexed TES operation are discussed, including possible readout noise and its mitigation. The prospects for the integration of large TES arrays into next-generation cryogenic experiments are outlined, with relevance extending beyond neutrinoless double beta decay searches to a broad class of low-temperature rare-event experiments.

Speaker: Vladyslav Berest

16:35 DMRadio-50L: Searching for Sub-μeV Axion Dark Matter

The DMRadio program is developing a suite of experiments to probe QCD axions in the sub-1 μeV mass range, a dark matter candidate with implications for grand unified theories and pre-inflationary cosmology. The first of these, DMRadio-50L, is undergoing commissioning and targets axion dark matter masses corresponding to frequencies from 5 kHz to 5 MHz. Accessing this low-mass QCD axion regime poses unique experimental challenges, requiring high-field magnets, ultra-sensitive superconducting quantum interference device (SQUID) readout, high-Q lumped-element resonators, and sophisticated data analysis techniques. I will present first commissioning data from DMRadio-50L including measurements of the systems cryogenic performance. I will also discuss future machine learning-driven denoising techniques, originally developed for the ABRACADABRA experiment, and their potential application to enhance sensitivity in axion searches.

Speaker: Jessica Fry

16:35 Evaluating radiation impact on transmon qubits in above and underground facilities

Superconducting qubits can be sensitive to abrupt energy deposits caused by cosmic rays and ambient radioactivity. While previous studies have explored correlated effects in time and space due to cosmic ray interactions, we present the direct comparison of a transmon qubit's performance measured at two distinct sites: the above-ground SQMS facility (Fermilab, US) and the deep-underground Gran Sasso Laboratory (Italy). Despite the stark difference in radiation levels, we observe a similar average qubit relaxation time of approximately 80 microseconds at both locations. To further investigate potential radiation-induced events, we employ a fast decay detection protocol, comparing the relative rates of triggered events between the two environments. Although intrinsic noise remains the dominant source of single errors in superconducting qubits, our analysis revealed a significant excess of radiation-induced events for high-coherence transmon qubits operated above-ground. Finally, using γ-ray sources with increasing activity levels, we evaluate the qubit response in a controlled low-background environment. In this contribution, we will present the work recently accepted for publication on EPJ Quantum Technology (https://arxiv.org/abs/2405.18355), and future prospects in this field.

Speaker: Alberto Ressa (Istituto Nazionale di Fisica Nucleare)

16:35 Kinetic Inductance Detector with integrated phonon collectors

Speaker: Leonardo Pesce (Istituto Nazionale di Fisica Nucleare)

16:35 Measuring quasiparticle dynamics for particle impact reconstruction in a superconducting qubit chip

When an ionizing particle interacts with the substrate of a superconducting qubit chip, it generates high-energy athermal phonons that propagate through the material, breaking Cooper pairs in the superconducting films and inducing quasiparticle poisoning. These non-equilibrium quasiparticles limit qubit coherence times and introduce correlated errors across large qubit arrays, posing a major challenge for the development of fault-tolerant quantum computers. At the same time, the potential sensitivity of superconducting qubits to Cooper pair breaking makes them promising detectors for dark matter and coherent elastic neutrino–nucleus scattering, given the meV-scale energy required for quasiparticle generation in most superconductors. In this work, we present a detailed statistical analysis of radiation-induced relaxation errors aimed at modeling the time evolution of quasiparticle density dynamics. From experimental data on five ground-plane transmon qubits, we extract the quasiparticle recombination constant with a precision of ≤10%. Furthermore, we investigate the correlation between the linear loss rate and the energy deposited in the qubit island. Finally, we introduce a statistical reconstruction method based on position localization to estimate the total energy deposited on the chip, providing a pathway toward using superconducting qubits as sensitive particle detectors.

Speaker: Emanuela Celi (Northwestern University)

16:35 Multiplexed operation of superconducting qubits for particle detection

The discovery that superconducting qubits are sensitive to ionizing radiation [1] has sparked interest beyond the quantum research community. Recent experiments, capable of detecting single interactions from cosmic muons [2, 3] and γ-rays [4], have highlighted the potential of these devices as a novel type of particle detector. As research in this field is still at an early stage, many questions remain open, especially regarding the propagation of phonons in the chip substrate and the reconstruction of the interaction point and energy deposited. In this framework, an important role is played by the study of correlated errors, i.e. simultaneous state decays of multiple qubits on the same chip.
In this contribution, we will present two fundamental building blocks for the investigation of correlated errors: a system for the multiplexed operation of up to four qubits, and a reset protocol for their simultaneous state preparation. The latter, in particular, is capable of preparing the qubits to different initial states, a flexibility uncommon in reset algorithms, and does not rely on specific hardware features, making it readily applicable to a wide range of superconducting qubit devices.

References:
1. Vepsäläinen et al., Impact of ionizing radiation on superconducting qubit coherence, Nature 584, 551-556 (2020), https://doi.org/10.1038/s41586-020-2619-8
2. Wilen et al., Correlated charge noise and relaxation errors in superconducting qubits, Nature 594, 369-373 (2021), https://doi.org/10.1038/s41586-021-03557-5
3. McEwen et al., Resolving catastrophic error bursts from cosmic rays in large arrays of superconducting qubits, Nat. Phys. 18, 107-111 (2022), https://doi.org/10.1038/s41567-021-01432-8
4. De Dominicis et al., Evaluating radiation impact on transmon qubits in above and underground facilities, EPJ Quantum Technol. (2026), https://doi.org/10.1140/epjqt/s40507-026-00490-2

Speaker: Francesco De Dominicis (Istituto Nazionale di Fisica Nucleare)

16:55 A Cryogenic Muon Tagging System Based on Kinetic Inductance Detectors for Superconducting Qubits

Several cutting-edge experiments using cryogenic superconducting devices are being developed to search for light Dark Matter, implementing innovative techniques for background suppression.
We propose a novel cryogenic muon tagging system based on Kinetic Inductance Detectors (KIDs) that achieves an efficiency exceeding 90% with negligible dead time. The muon tagging system has been specifically developed for superconducting qubits, an emerging technology in Dark Matter detection, to veto operations affected by muon-induced errors. Thanks to its simple design and fabrication, as well as the capability to read multiple devices on a single readout line, the tagging system is easily adaptable to a wide range of cryogenic detectors.
In this contribution, we present the performance of the muon tagging system, first installed on a phonon-mediated KID similar to those developed within the CALDER project, and subsequently on a high-$T_1$ qubit chip developed within the SQMS center.

Speaker: Letizia Tirabasso (Istituto Nazionale di Fisica Nucleare)

16:55 Abstract Poster STDM Rome 2026 Giosue Sardo Infirri April 17, 2026 QUAX Ferromagnetic haloscope read out by a Single Microwave Photon Counter

The search for axions, light and weakly interacting dark matter particles, is nowadays mostly
exploited through photon coupling in the sub-meV region. In this range, only haloscopes have a
sensitivity to test theoretically motivated axion models. (talk by Di Vora for the last updates on
the QUAX haloscope[1])
Axions can also be exploited through coupling to fermions, but no experiment is able to reach the
required sensitivity in the sub-meV mass range to this date.
Recently, Single Microwave Photon Detectors (SMPDs), chips comprised of two resonators coupled
to a superconducting qubit, have been demonstrated to increase the sensitivity to axion signals in a
haloscope [2]. The SMPD resolution is a single microwave photon, which allows them to overcome
the so-called Standard Quantum Limits of linear amplifiers.
This novel improvement is now being implemented on a ferromagnetic haloscope[3] to further en-
hance the sensitivity to axions through coupling to the electron. The hypothetical axion signal will
excite the magnon mode of a ferromagnetic material (YIG in our case) inserted inside the haloscope
cavity. Under the condition of strong coupling, the hybrid mode polariton-magnon can be picked
up and read out with the SMPD.
The axion mass tuning is performed by varying the magnetic field acting on the ferromagnetic
material. The range to be probed, from 7.2 to 7.4 GHz, will also test the ability to downscale such
haloscopes.
References
[1] G Sardo Infirri et al. “Search for Postinflationary QCD Axions with a Quantum-Limited Tun-
able Microwave Receiver”. In: Physical Review Letters 135.21 (2025), p. 211002.
[2] Caterina Braggio et al. “Quantum-enhanced sensing of axion dark matter with a transmon-
based single microwave photon counter”. In: Physical Review X 15.2 (2025), p. 021031.
[3] N Crescini et al. “Axion search with a quantum-limited ferromagnetic haloscope”. In: Physical
Review Letters 124.17 (2020), p. 171801.

Speaker: Giosue' Sardo Infirri (Istituto Nazionale di Fisica Nucleare)

16:55 BULLKID-DM: searching for light WIMPs with monolithic detector arrays

Speaker: Matteo Cappelli (Istituto Nazionale di Fisica Nucleare)

16:55 Instrumentation of frequency-division multiplexed cryogenic detectors

Modern experiments in particle and astroparticle physics are increasingly relying on low-temperature detectors to achieve unprecedented sensitivities. Common applications of these detectors include efforts to determine the absolute neutrino mass scale, search for neutrinoless double beta decay, and detection of potential dark matter candidates. Achieving these goals with high energy resolution requires the simultaneous readout of large-scale arrays of cryogenic detectors, often ranging in the tens or hundreds of thousands of pixels. Frequency-Division Multiplexing (FDM) readout techniques, such as microwave SQUID multiplexing, are critical enablers of these ambitious programs.
For operation of FDM cryogenic detector arrays, we are developing the
Quantum Interface Controller (QIC), a modular and scalable room-temperature readout system shared across several experiments. This system supports full-stack end-to-end signal processing, including digital synthesis of the required microwave tones as well as real-time demodulation of the detector signals using FPGA-based firmware. A corresponding Python API enables user-friendly configuration of the system and processing of the acquired data. The readout electronics are designed to be adaptable to the specific needs of experiments, to improve development efficiency, and long-term maintainability. Currently, the
system is deployed in ECHo (neutrino mass), BULLKID-DM (dark matter),
and a proposed upgrade of QUBIC (CMB).
We present the architecture of this multi-purpose readout system, discuss the supported QIC hardware variants and describe the modular implementation of the signal processing firmware. This contribution provides an overview of the current status and will show possibilities for future applications.

Authors: T. Muscheid$^1$, L.E. Ardila-Perez$^1$, D.A. Crovo P´erez$^1$, M. Fuchs$^1$, R. Gartmann$^1$, L. Scheller$^1$, and F. Simon$^1$
$^1$Institute for Data Processing and Electronics (IPE), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany

Speaker: Timo Philipp Muscheid

16:55 Progress towards the BULLKID-DM experiment: development of the veto system and the calibrator.

BULLKID-DM is a cryogenic experiment, carried out at the Laboratori Nazionali del Gran Sasso (LNGS) in
Italy, that will search for ≤ 1GeV/c2WIMP dark matter particles with nucleon cross-sections below 10−41cm2.The
main detector consists of an 800g array of over 2000 silicon dice, each acting as a particle absorber instrumented
with multiplexed Kinetic Inductance Detectors (KIDs). The experiment is designed to probe energy deposits in the
region (200 eV - 5 keV).
For rare-event search experiments such as BULLKID-DM, it is crucial to minimise background signals from
muons, photons and neutrons. One possible way to achieve such low background is to use a cryogenic anti-
coincidence veto system. The veto consists of a tessellated structure of scintillating crystals whose light output is
read out by phonon-mediated KIDs.
Another main challenges of the experiment is the development of an in-situ calibration system. Given the
multiple layers of shielding materials and the cryogenic veto that surround the experiment, introducing a calibration
source in the proximity of the detector is non-trivial. We intend to use the X-rays from an 241Am source which
needs to be accurately positioned and needs to be easily stowed away.
These two subsystems are currently being developed at the Pisa section of the National Institute for Nuclear
Physics (INFN) and will be the object of this contribution

Speakers: Mario De Lucia (Istituto Nazionale di Fisica Nucleare), Tommaso Lari (Istituto Nazionale di Fisica Nucleare), Giulia Spina (Istituto Nazionale di Fisica Nucleare), Matteo Del Gallo Roccagiovine

16:55 Searching for Dark Matter with Hybrid Quantum Circuits

In 1983, Pierre Sikivie developed an idea that would allow us to detect the conversion of an axion — one of the promising candidates for dark matter — into a photon. via the Inverse Primakoff effect. By constructing a cavity whose resonance frequency would be in tune with the axion frequency, we can increase the coupling between the electric field inside the cavity and the axion field by applying a magnetic field to the system, which would then allow us to drive and measure the presence of the axion through direct detection.

By utilizing a tripartite system comprised of a magnetic field resilient superconducting device, a microwave cavity, and an antiferromagnetic crystal, we aim to detect dark matter with an architecture akin to Pierre Sikivie’s, wihile also exploring the exotic electrodynamics associated with the axion by investigating topological axion insulators with a similar experimental setup. Here, we show the tunability of the cavity resonance frequency owing to the ultra strong coupling between the cavity and the magnetic crystal, as well as theoretical calculations for the magnetic modes dispersions exhibited from our topological materials.

Speaker: Kenta Kodama

16:55 The DarkDot Experiment

The DarkDot experiment is a search for light dark matter utilizing Quantum Dots as the detector medium and Superconducting Nanowire Single Photon Detectors (SNSPDs) as photon sensors. Quantum Dots are nanocrystals that are highly customizable, allowing for precise tuning of the energy needed for scintillation, the type of interaction allowed, and the wavelength of the scintillation photon. This flexibility would allow us to probe different Dark matter candidates and interactions in a single experiment. The differences in the quantum dots can also help with background discrimination. These Quantum Dots will then be coupled with SNSPDs to detect the scintillation light, taking advantage of the SNSPDs' high quantum efficiency and low dark counts. Our current work is focused on increasing the size of the SNSPDs to be used in DarkDot and other dark matter searches with collaborators at MIT. I will present on these experimental results and the plans for the future DarkDot experiment.

Speaker: Nora Hoch (MIT)

16:55 Transmon Qubit as Single Photon Detector for Axion Searches in the RADES Experiment

RADES (Relic Axion Detection Exploratory Setup) is a haloscope experiment designed to search for axions originating from the local dark matter galactic halo in the μeV mass range, under the assumption that dark matter is entirely composed of axions. The detection technique relies on a resonant cavity immersed in a strong magnetic field to enhance the conversion of axions into detectable photons. The collaboration has achieved significant progress in the development of novel cavity geometries, leading to two physics results at axion masses around 30 $\mu$eV.
To maximise the signal-to-noise ratio, the experiment operates at cryogenic temperatures using a dilution refrigerator capable of reaching approximately 10 mK. At such extreme low temperatures, superconducting devices, such as transmon qubits, can be employed as single-photon detectors, further improving signal sensitivity.
Thanks to the recently awarded ERC-SYG “Dark Quantum”, an innovative setup incorporating transmon qubits is currently being developed and tested within the collaboration. In this contribution, we present the first results of this endeavour obtained at the Max Planck Institute for Physics in Garching.

Speaker: Elisa Gabbrielli (Max Planck Institut für Physik)

17:20 → 18:35 Readout

Convener: Angelo Cruciani (Istituto Nazionale di Fisica Nucleare)

17:20 Data Acquisition Systems for High Energy Physics and Quantum Sensors

Data acquisition systems are an essential backbone of modern experiments, in many cases defining overall performance in terms of data output and experimental statistics. Experiments at high-energy particle colliders, which push the limits of overall data throughput, and dark matter searches and precision experiments with often stringent constraints on physical connections and power budget in cryogenic volumes both profit from advances in programmable microelectonics. An overview over developments in both areas at the KIT Institute for Data Processing and Electronics will be given, highlighting connections between both classes of applications.

Speaker: Frank Simon

17:45 SMuRF and SPECTRA: scalable readout for superconducting dark matter sensors

The SLAC Microresonator RF (SMuRF) electronics is a warm readout platform deployed at scale in CMB experiments to drive ~2000-channel microwave SQUID multiplexed transition-edge sensor arrays. Building on this foundation, the platform is being extended to support a broader range of superconducting sensors relevant to dark matter and rare-event searches, including fast pulse reconstruction in low-mass calorimeters, continuous-wave dispersive monitoring of qubit-based sensors such as SQUATs and QPDs, and pulse-driven control of single microwave photon detectors. I will review SMuRF and show recent results from operation with other sensing modalities, including MKIDs and SQUATs on RFSoC-based prototypes. I will then introduce SPECTRA, a multi-institutional effort with Fermilab (QICK), the University of Chicago, and partner groups across the dark matter and line-intensity-mapping user communities. SPECTRA will be a fully RFSoC-based, multi-mode open-source stack running on evaluation boards, QICK hardware, and ATCA-deployable carriers.

Speaker: Zeesh Ahmed (Kavli Institute of Particle Astrophysics and Cosmology, SLAC/Stanford)

18:10 Readout technology for superconducting dark matter searches

The diverse and challenging requirements of dark matter searches motivate the development of new readout technologies. Relevant performance metrics include input noise, frequency range, bandwidth, resistance to magnetic field, and compatibility with a variety of sensors and sensor architectures. In this presentation I describe work at NIST on several superconducting readout technologies relevant to dark matter searches. These include the microwave SQUID multiplexer, parametric amplifiers, and Kinetic Inductance Current Sensors (KICs). Some of these devices have already been used in dark matter searches while others show potential for future experiments.

Speaker: Joel Ullom

20:30 → 23:00 Dinner: La Limonaia (Via Lazzaro Spallanzani, 1/A)

--La Limonaia--
Via Lazzaro Spallanzani, 1/A, 00161 Roma RM
+39 06 9506 5250

Wednesday 13 May

09:00 → 10:40 Axion Sensing 2

Convener: BERNARD VAN HECK

09:00 Superconducting Sensors and Photonics for HAYSTAC and ALPHA

Microwave cavity-based dark matter axion searches are presented with two challenges to achieving credible discovery potential. The first, common to searches at all axion masses, is achieving the requisite sensitivity, which has been a driver for quantum sensing. The HAYSTAC experiment has been a leader in the development of superconducting devices for the post-inflation axion, including the flux-pumped Josephson Parametric Amplifier which enabled the first quantum-limited dark matter axion search, and a squeezed-state receiver which circumvented the Standard Quantum Limit entirely, increasing its scan rate by a factor of two. An even more powerful scheme, two-cavity entanglement and state exchange has been demonstrated on the bench and is being prepared for operation next year. The second challenge is extending the mass (frequency) range upward or downward to where conventional microwave cavities are no longer viable. Pushing up further into the post-inflation mass range, the ALPHA experiment will incorporate a wire-array metamaterial resonator whose plasma frequency can be designed for the 10-50 GHz range with large volume. At sufficiently high frequencies, owing to the density of wire elements, metamaterial resonators will need to be superconducting to achieve a suitably high quality factor, for which an active R&D program is ongoing.

Speaker: Karl Van Bibber

09:25 SQUATs: Qubit-Based Sensors for Dark Matter

The Superconducting Quasiparticle-Amplifying Transmon (SQUAT) is a sensor architecture for meV (THz) detection based on a weakly charge-sensitive transmon qubit directly coupled to a transmission line. Energy depositions in the qubit capacitor generate quasiparticles that tunnel across the Josephson junction. Each tunnel changes the qubit parity and produces a measurable signal in CW transmission. SQUATs use junctions with lower-Tc than their capacitors to induce quasiparticle trapping near the junction and amplify the tunneling rate for a given energy deposition. Their enhanced sensitivity to quasiparticle events and intrinsic multiplexability make SQUATs a promising detector foundation for low-energy-threshold rare-event searches. In this talk, I will present the design and characterization of SQUAT-style detectors, including the newest generation of SQUATs with Ta-Al quasiparticle trapping and silicon target substrates. I will discuss background sources that influence the observed parity-switching rate as well as progress towards a position-dependent calibration using MEMS-based cryogenic optical beam steering.

Coauthors: Hannah Magoon (Stanford University / SLAC National Accelerator Laboratory), Taj Dyson (Stanford University / SLAC National Accelerator Laboratory), Grace Bratrud (Northwestern University), Alexander Droster (SLAC National Accelerator Laboratory), Riley Carpenter (Stanford University), Zachary Gillis (Stanford University), Jadyn Anczarski (Stanford University / SLAC National Accelerator Laboratory), Caleb Fink (Syracuse University), Aviv Simchony (Stanford University / SLAC National Accelerator Laboratory), Zoë Smith (Stanford University / SLAC National Accelerator Laboratory), Noah Kurinsky (Stanford University / SLAC National Accelerator Laboratory), Shannon Harvey (Stanford University / SLAC National Accelerator Laboratory), Chiara Salemi (UC Berkeley/LBNL), Betty Young (Santa Clara University), David Schuster (Stanford University / SLAC National Accelerator Laboratory)

Speaker: Taylor Aralis

09:50 Superconducting TWPAs in Dark Matter Searches

Ultralight bosonic dark matter candidates, such as axions, axion-like particles, and dark photons, can behave as classical coherent fields oscillating at frequencies set by the particle mass. In the microwave regime, this motivates detection strategies based on superconducting quantum devices, where near-quantum-limited amplification and single-excitation sensitivity can probe extremely weak interactions.

We present two complementary superconducting approaches. First, we describe a kinetic inductance traveling wave parametric amplifier (KTWPA) based on 10 nm-thick NbTiN films targeting the 10–14 GHz band, intended as the readout amplifier for broadband dish antenna experiments such as GigaBREAD, which simultaneously scan a wide frequency range in search of bosonic dark matter. Building on prior generations with >20 dB gain and near-quantum-limited noise over 4–8 GHz [1], KTWPAs are particularly well suited for axion searches as they are resilient to the Tesla-scale magnetic fields required for detection. We report on gain, bandwidth, and noise performance of these next-generation devices.

Second, we present a transmon-based direct detection scheme in which a flux-tunable qubit acts as an absorptive sensor for dark matter-induced electromagnetic excitations. Broadband exploration is achieved by sweeping the qubit frequency through repeated interaction and readout cycles. We further introduce a quantum-enhanced protocol coupling two sensing qubits to a common ancilla with post-selection, amplifying the sensor response to small excitation probabilities [2]. A noise-aware analysis quantifies the sensitivity gain over direct single-qubit sensing.

Together, these approaches represent a scalable strategy for probing new dark sector parameter space with superconducting quantum hardware.

References:
[1] L. Howe, A. Giachero et al. arXiv:2507.07706 [quant-ph]
[2] R. Moretti at al. arXiv:2603.03157 [quant-ph]

Authors:
A. Giachero(1,2,3,4), J. Austermann(4), D. A. Bennett(4), S. P. Benz(4), M. Borghesi(1,2), P. Campana(1,2), R. Carobene(1,2), A. Cattaneo(1,2), M. A. Castellanos-Beltran(4), M. Erickson(5,4), M. Faverzani(1,2), E. Ferri(2), M. Gobbo(1,2), L. Howe(3,4), P. F. Hopkins(4), J. Hubmayr(4), D. I. Olaya(3,4), D. Labranca(1,2), R. Moretti(1,2), A. Nucciotti(1,2), A. J. Sirois(4), C. Shiu(4), P. Szypryt(4), J.N. Ullom(3,4), M.R. Vissers(4), J.D. Wheeler(4)

1 Department of Physics, University of Milano-Bicocca, Milan, 20126, Italy
2 INFN - Milano-Bicocca, Milan, 20126, Italy
3 Department of Physics, University of Colorado, Boulder, Colorado 80309, USA
4 National Institute of Standards and Technology, Boulder, Colorado 80305, USA
5 Department of Electrical, Energy, and Computer Engineering, University of Colorado, Boulder, 80309, Colorado

Speaker: Dr Andrea Giachero

10:15 High-Q Cavities and Quantum Sensing Platforms for Fundamental Physics at SQMS

The SQMS Center develops state-of-the-art superconducting technologies for ultra-sensitive searches for physics beyond the Standard Model. Central to this effort are superconducting cavities with world-record quality factors, operating as precision sensors for extremely weak signals. When integrated with superconducting devices, these systems can enable even further enhanced sensitivity and faster scanning of parameter space. SQMS researchers are advancing a broad program of quantum sensing experiments targeting dark matter and other BSM physics, including axion and dark photon searches, light-shining-through-wall experiments, and cavity-based detection of high-frequency gravitational waves. This talk will highlight the underlying technologies and discuss current and upcoming experimental efforts.

Speaker: Bianca Giaccone

10:40 → 11:10 Break

11:10 → 12:50 Axions Haloscopes

Convener: Marco Vignati (Istituto Nazionale di Fisica Nucleare)

11:10 The CADEx Experiment: Exploiting Superconducting Technologies for Axion Searches

The Canfranc Axion Detection Experiment (CADEx) will search for axions in the yet unexplored mass range of 330–460 micro–electronvolts (µeV). Operating in the W-band (75–110 GHz), CADEx will be installed in a dilution cryostat at the Canfranc Underground Laboratory, combining, for the first time, a cavity haloscope in a strong magnetic field with a Kinetic Inductance Detector (KID) camera. This novel combination is designed to detect the polarization signature of the axion.
Achieving the necessary sensitivity requires advances in two key areas: signal generation and detection. Superconducting technologies provide a key advantage in both. On the one hand, superconducting coatings enhance the performance of the cavities within the haloscope; on the other, superconducting KIDs enable sensitivities that surpass those of traditional HEMT amplifiers. In this talk, I will present the CADEx experiment and the developments achieved over the last years through the use of superconducting technologies.

Speaker: Alicia Gomez

11:35 Tuning in to low-mass axions with the DMRadio program

Axions are one of the most compelling answers to the open question of the identity of the universe’s dark matter. Detecting them is challenging, due to their tiny expected couplings to visible matter and their very low, unknown mass. The DMRadio program is working to overcome these challenges to search for low-mass axion dark matter using a lumped-element detection technique. Here I will present the detection concept as well as progress on the two current experiments, DMRadio-50L and CAL-Pathfinder. I will also talk about the path forward toward detecting GUT-motivated QCD axions.

Speaker: Chiara Salemi

12:00 Advancing Axion and Gravitational Wave Searches at LNF

Understanding the nature of dark matter remains one of the most compelling and urgent questions in modern physics. Simultaneously, the groundbreaking discovery of gravitational waves has opened an entirely new observational window onto the Universe, allowing scientists to explore cosmic phenomena previously hidden from view using traditional electromagnetic methods. Looking ahead, the high-frequency regime—ranging from MHz to GHz—holds the potential to reveal an unexplored frontier of astrophysical and cosmological processes.

The INFN National Laboratories in Frascati (LNF) are actively engaged in axion dark matter research and are poised to play a leading role in the search for high-frequency gravitational waves (HFGWs) through their involvement in GravNet. GravNet is a planned network of cryogenic detectors—originally designed as haloscopes for axion detection—repurposed and optimized for gravitational wave observation in the high-frequency band. By extending the accessible parameter space, GravNet could pave the way toward the first detection of high-frequency gravitational waves.

Currently, one haloscope is operational at LNF as part of the QUAX experiment, while a second, FLASH, is under development. FLASH will make use of the 3-meter bore magnet formerly employed in the FINUDA experiment.

Complementing these efforts, the COLD lab team at INFN Frascati (coldlab.lnf.infn.it) is developing advanced superconducting qubit-based devices to enhance the sensitivity of these detectors. Superconducting qubits offer tremendous potential, but their integration into strong magnetic field environments presents significant technical challenges. Overcoming these obstacles involves either transporting signals to magnetically shielded areas or engineering qubits that are inherently resilient to such fields. Additionally, readout errors from noise and qubit dephasing can degrade sensitivity—issues that can be addressed using quantum non-demolition techniques, including repeated measurements or the deployment of multiple qubits operating in parallel.

Speaker: Claudio Gatti (Istituto Nazionale di Fisica Nucleare)

12:25 Hunting for QCD Axion Dark Matter with the Princeton Axion Search

I discuss the latest developments on the Princeton Axion Search (PXS), a search for QCD axion dark matter in the 0.8-2.1 ueV mass range (200-500 MHz frequencies). PXS addresses the transitional range between cavity haloscopes and the DMRadio program, which operates below any cavity modes and utilizes lumped-element techniques. I describe development efforts on all aspects of the experimental apparatus, including the cryogenics, solenoidal magnet, near-quantum-limited readout amplifiers, and resonator. PXS leverages a partnership with the DOE Princeton Plasma Physics Laboratory to design and construct a large-bore, conduction-cooled solenoid. It also benefits from a partnership with Caltech/NASA JPL to implement parametric amplifiers in this frequency range. PXS is developing superconducting resonators and readouts beyond the Standard Quantum Limit of amplification in collaboration with the DMRadio program, which aims to probe the lower sub-ueV mass range. I discuss some of these collaborative efforts.

Speaker: Saptarshi Chaudhuri

12:50 → 13:00 Final Remarks

12:50 Final Remarks

Speakers: Lindley Anne Winslow (MIT), Marco Vignati (Istituto Nazionale di Fisica Nucleare)