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A First Demonstration of the SQUAT Detector Architecture: Direct Measurement of Resonator-Free Charge-Sensitive Transmons
Authors:
H. Magoon,
T. Aralis,
T. Dyson,
J. Anczarski,
D. Baxter,
G. Bratrud,
R. Carpenter,
S. Condon,
A. Droster,
E. Figueroa-Feliciano,
C. W. Fink,
S. Harvey,
A. Simchony,
Z. J. Smith,
S. Stevens,
N. Tabassum,
B. A. Young,
C. P. Salemi,
K. Stifter,
D. I. Schuster,
N. A. Kurinsky
Abstract:
The Superconducting Quasiparticle-Amplifying Transmon (SQUAT) is a new sensor architecture for THz (meV) detection based on a weakly charge-sensitive transmon directly coupled to a transmission line. In such devices, energy depositions break Cooper pairs in the qubit capacitor islands, generating quasiparticles. Quasiparticles that tunnel across the Josephson junction change the transmon qubit par…
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The Superconducting Quasiparticle-Amplifying Transmon (SQUAT) is a new sensor architecture for THz (meV) detection based on a weakly charge-sensitive transmon directly coupled to a transmission line. In such devices, energy depositions break Cooper pairs in the qubit capacitor islands, generating quasiparticles. Quasiparticles that tunnel across the Josephson junction change the transmon qubit parity, generating a measurable signal. In this paper, we present the design of first-generation SQUATs and demonstrate an architecture validation. We summarize initial characterization measurements made with prototype devices, comment on background sources that influence the observed parity-switching rate, and present experimental results showing simultaneous detection of charge and quasiparticle signals using aluminum-based SQUATs.
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Submitted 22 January, 2026;
originally announced January 2026.
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Noise Modeling and Calibration of a Two-Stage Cryogenic Charge Amplifier for the SPLENDOR Experiment
Authors:
Jadyn Anczarski,
Owen Andrews,
Taylor Aralis,
Caleb Fink,
Noah Kurinsky,
Arran Phipps,
Aditi Pradeep,
Betty A. Young
Abstract:
The SPLENDOR Collaboration studies novel narrow-gap semiconductors and engineered a substrate agnostic detector platform to achieve $\mathcal{O}$(meV) energy sensitivity designed for low mass dark matter searches. This was achieved using low-capacitance and low-noise commercial CryoHEMTs in a split-stage topology integrated throughout a dilution refrigerator. Designed with a source-follower HEMT a…
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The SPLENDOR Collaboration studies novel narrow-gap semiconductors and engineered a substrate agnostic detector platform to achieve $\mathcal{O}$(meV) energy sensitivity designed for low mass dark matter searches. This was achieved using low-capacitance and low-noise commercial CryoHEMTs in a split-stage topology integrated throughout a dilution refrigerator. Designed with a source-follower HEMT at the base temperature stage and a voltage amplifier at 4\,K, this amplifier has input-limited voltage noise of 10 $\text{nV}/\sqrt{\text{Hz}}$ and current noise of 100 $\text{aA}/\sqrt{\text{Hz}}$ at 1kHz. In agreement with this noise level and a photon calibration, this amplifier has a $\text{19} \pm \text{4} $ electron resolution.
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Submitted 1 October, 2025;
originally announced October 2025.
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Search for low-mass electron-recoil dark matter using a single-charge sensitive SuperCDMS-HVeV Detector
Authors:
SuperCDMS Collaboration,
M. F. Albakry,
I. Alkhatib,
D. Alonso-González,
J. Anczarski,
T. Aralis,
T. Aramaki,
I. Ataee Langroudy,
C. Bathurst,
R. Bhattacharyya,
A. J. Biffl,
P. L. Brink,
M. Buchanan,
R. Bunker,
B. Cabrera,
R. Calkins,
R. A. Cameron,
C. Cartaro,
D. G. Cerdeño,
Y. -Y. Chang,
M. Chaudhuri,
J. -H. Chen,
R. Chen,
N. Chott,
J. Cooley
, et al. (124 additional authors not shown)
Abstract:
We present constraints on low-mass dark matter electron scattering and absorption interactions using a SuperCDMS high-voltage eV-resolution (HVeV) detector. Data were taken underground in the NEXUS facility located at Fermilab with an overburden of 225 meters of water equivalent. The experiment benefits from the minimizing of luminescence from the printed circuit boards in the detector holder used…
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We present constraints on low-mass dark matter electron scattering and absorption interactions using a SuperCDMS high-voltage eV-resolution (HVeV) detector. Data were taken underground in the NEXUS facility located at Fermilab with an overburden of 225 meters of water equivalent. The experiment benefits from the minimizing of luminescence from the printed circuit boards in the detector holder used in all previous HVeV studies. A blind analysis of $6.1\,\mathrm{g\cdot days}$ of exposure produces exclusion limits for dark matter-electron scattering cross sections for masses as low as $1\,\mathrm{MeV}/c^2$, as well as on the photon-dark photon mixing parameter and the coupling constant between axionlike particles and electrons for particles with masses $>1.2\,\mathrm{eV}/c^2$ probed via absorption processes.
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Submitted 15 March, 2026; v1 submitted 3 September, 2025;
originally announced September 2025.
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Multi-channel, multi-template event reconstruction for SuperCDMS data using machine learning
Authors:
M. F. Albakry,
I. Alkhatib,
D. Alonso-Gonzalez,
J. Anczarski,
T. Aralis,
T. Aramaki,
I. Ataee Langroudy,
C. Bathurst,
R. Bhattacharyya,
A. J. Biff,
P. L. Brink,
M. Buchanan,
R. Bunker,
B. Cabrera,
R. Calkins,
R. A. Cameron,
C. Cartaro,
D. G. Cerdeno,
Y. -Y. Chang,
M. Chaudhuri,
J. H. Chen,
R. Chen,
N. Chott,
J. Cooley,
H. Coombes
, et al. (117 additional authors not shown)
Abstract:
SuperCDMS SNOLAB uses kilogram-scale germanium and silicon detectors to search for dark matter. Each detector has Transition Edge Sensors (TESs) patterned on the top and bottom faces of a large crystal substrate, with the TESs electrically grouped into six phonon readout channels per face. Noise correlations are expected among a detector's readout channels, in part because the channels and their r…
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SuperCDMS SNOLAB uses kilogram-scale germanium and silicon detectors to search for dark matter. Each detector has Transition Edge Sensors (TESs) patterned on the top and bottom faces of a large crystal substrate, with the TESs electrically grouped into six phonon readout channels per face. Noise correlations are expected among a detector's readout channels, in part because the channels and their readout electronics are located in close proximity to one another. Moreover, owing to the large size of the detectors, energy deposits can produce vastly different phonon propagation patterns depending on their location in the substrate, resulting in a strong position dependence in the readout-channel pulse shapes. Both of these effects can degrade the energy resolution and consequently diminish the dark matter search sensitivity of the experiment if not accounted for properly. We present a new algorithm for pulse reconstruction, mathematically formulated to take into account correlated noise and pulse shape variations. This new algorithm fits N readout channels with a superposition of M pulse templates simultaneously - hence termed the N$\times$M filter. We describe a method to derive the pulse templates using principal component analysis (PCA) and to extract energy and position information using a gradient boosted decision tree (GBDT). We show that these new N$\times$M and GBDT analysis tools can reduce the impact from correlated noise sources while improving the reconstructed energy resolution for simulated mono-energetic events by more than a factor of three and for the 71Ge K-shell electron-capture peak recoils measured in a previous version of SuperCDMS called CDMSlite to $<$ 50 eV from the previously published value of $\sim$100 eV. These results lay the groundwork for position reconstruction in SuperCDMS with the N$\times$M outputs.
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Submitted 27 August, 2025;
originally announced August 2025.
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Low-Energy Calibration of SuperCDMS HVeV Cryogenic Silicon Calorimeters Using Compton Steps
Authors:
SuperCDMS Collaboration,
M. F. Albakry,
I. Alkhatib,
D. Alonso-Gonźalez,
D. W. P. Amaral,
J. Anczarski,
T. Aralis,
T. Aramaki,
I. Ataee Langroudy,
C. Bathurst,
R. Bhattacharyya,
A. J. Biffl,
P. L. Brink,
M. Buchanan,
R. Bunker,
B. Cabrera,
R. Calkins,
R. A. Cameron,
C. Cartaro,
D. G. Cerdeño,
Y. -Y. Chang,
M. Chaudhuri,
J. -H. Chen,
R. Chen,
N. Chott
, et al. (126 additional authors not shown)
Abstract:
Cryogenic calorimeters for low-mass dark matter searches have achieved sub-eV energy resolutions, driving advances in both low-energy calibration techniques and our understanding of detector physics. The energy deposition spectrum of gamma rays scattering off target materials exhibits step-like features, known as Compton steps, near the binding energies of atomic electrons. We demonstrate a succes…
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Cryogenic calorimeters for low-mass dark matter searches have achieved sub-eV energy resolutions, driving advances in both low-energy calibration techniques and our understanding of detector physics. The energy deposition spectrum of gamma rays scattering off target materials exhibits step-like features, known as Compton steps, near the binding energies of atomic electrons. We demonstrate a successful use of Compton steps for sub-keV calibration of cryogenic silicon calorimeters, utilizing four SuperCDMS High-Voltage eV-resolution (HVeV) detectors operated with 0 V bias across the crystal. This new calibration at 0 V is compared with the established high-voltage calibration using optical photons. The comparison indicates that the detector response at 0 V is about 30% weaker than expected, highlighting challenges in detector response modeling for low-mass dark matter searches.
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Submitted 9 December, 2025; v1 submitted 4 August, 2025;
originally announced August 2025.
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SPLENDOR: a novel detector platform to search for light dark matter with narrow-gap semiconductors
Authors:
P. Abbamonte,
A. Albert,
D. S. M. Alves,
J. Anczarski,
T. Aralis,
T. U. Böhm,
C. Boyd,
J. Chen,
P. -H. Chu,
M. S. Cook,
C. W. Fink,
M. L. Graesser,
Y. Kahn,
C. S. Kengle,
T. Kucinski,
N. A. Kurinsky,
C. Lane,
A. Leder,
R. Massarczyk,
A. Mazumdar,
S. J. Meijer,
W. Nie,
E. A. Peterson,
A. Phipps,
F. Ronning
, et al. (9 additional authors not shown)
Abstract:
We present the design and current status of SPLENDOR, a novel detector platform that combines narrow-gap semiconductor targets with low-noise charge readout to achieve sensitivity to dark matter energy deposits well below the eV scale. SPLENDOR is designed to be a modular and scalable system able to accommodate different target materials and signal readout technologies. SPLENDOR's present strategy…
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We present the design and current status of SPLENDOR, a novel detector platform that combines narrow-gap semiconductor targets with low-noise charge readout to achieve sensitivity to dark matter energy deposits well below the eV scale. SPLENDOR is designed to be a modular and scalable system able to accommodate different target materials and signal readout technologies. SPLENDOR's present strategy entails: (i) the use of strongly correlated f-electron semiconductors with anisotropic electronic structures to enable not only sub-eV energy thresholds, but also directional sensitivity to the incoming dark matter flux, allowing for signal-background discrimination via daily modulation, and (ii) custom charge readout based on cryogenic high-electron-mobility transistor (cryoHEMT) amplifiers approaching single-electron resolution. We report on the selection and characterization of Eu$_5$In$_2$Sb$_6$ as the target material for SPLENDOR's first prototype detector, as well as the development and calibration of the prototype amplifier chain, achieving a measured charge resolution of 20$\pm$7 electrons in silicon test samples, consistent with predicted performance. This provides a demonstration of the detector architecture, which is now ready for deployment in a dark matter search campaign to deliver SPLENDOR's first science results. Finally, we present estimates of sensitivity reach in the parameter space of athermally produced relic dark matter under high- and low-background environments, and for various amplifier technology upgrades with increasing performance, including planned quantum sensing upgrades in order to achieve our ultimate goal of sub-electron resolution in optimized systems. SPLENDOR provides a novel approach to dark matter direct detection, combining quantum sensing with material's design to open new avenues of exploration in the sub-MeV mass range of dark matter parameter space.
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Submitted 15 August, 2025; v1 submitted 23 July, 2025;
originally announced July 2025.
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Correcting impedance measurements for background parasitics to characterize circuit components in cryogenic environments
Authors:
Riley J. Carpenter,
Jadyn Anczarski,
Ivar Rydstrom,
Aviv Simchony,
Zoe J. Smith,
Noah A. Kurinsky,
Betty A. Young
Abstract:
Predictable circuit response is a critical prerequisite for accurate electronic measurements. We describe a powerful, yet straightforward, experimental method and analysis model that utilizes an affordable LCR meter in conjunction with an in situ parasitic impedance background correction procedure to measure the temperature-dependent impedance (magnitude and phase) of individual passive circuit el…
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Predictable circuit response is a critical prerequisite for accurate electronic measurements. We describe a powerful, yet straightforward, experimental method and analysis model that utilizes an affordable LCR meter in conjunction with an in situ parasitic impedance background correction procedure to measure the temperature-dependent impedance (magnitude and phase) of individual passive circuit elements mounted in a cryostat. We show how the model unambiguously identified a 20x drop in capacitance for 22 microF 5XR multilayer ceramic capacitors cooled from 300 K to 360 mK in an environment with parasitic capacitance of order 300 pF. The same experimental procedure, based on a simple two-wire measurement, was also used to successfully measure 10 pF and 22 pF thin-film capacitors and 100 MOhm thick-film resistors. The results showed that the resistor values increased by up to an order of magnitude when the devices were cooled from 300 K to 360 mK. Most importantly, the simple data acquisition method and robust analysis model were shown to effectively extend the accuracy of a simple benchtop LCR meter beyond its manufacturer-guaranteed values for a wide range of measurement frequencies.
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Submitted 13 June, 2025;
originally announced June 2025.
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Broadband Optical Modulation and Control at Millikelvin Temperatures
Authors:
N. Tabassum,
T. Aralis,
J. Anczarski,
D. Baxter,
B. Cabrera,
R. Chapla,
N. Entin,
L. Hsu,
H. W. Magoon,
A. Nunez,
J. L. Ryan,
M. Salatino,
A. Simchony,
Z. J. Smith,
S. Stevens,
G. Pérez,
H. Stueber,
B. A. Young,
N. A. Kurinsky,
K. Stifter
Abstract:
A universal experimental challenge when studying radiation effects on cryogenic devices is to precisely and accurately characterize the position-dependent device response very near the energy detection threshold. We have developed a compact cryogenic optical beam steering system that can be used to generate O(μs) pulses of small numbers of photons over the energy range of 1.2 - 4.5eV at room tempe…
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A universal experimental challenge when studying radiation effects on cryogenic devices is to precisely and accurately characterize the position-dependent device response very near the energy detection threshold. We have developed a compact cryogenic optical beam steering system that can be used to generate O(μs) pulses of small numbers of photons over the energy range of 1.2 - 4.5eV at room temperature, and deliver those photons via fiber optic to any specified location on the surface of a detector operating at cryogenic temperatures. This new system will allow for robust calibration of any photon-sensitive detector, including supercondcting devices. The system can be used efficiently to explore the physics of target materials, quantify the position sensitivity of different sensor designs, measure phonon transport, and study the effects of quasiparticle poisoning on detector operation. We describe the design of this pulsed calibration method and present first results obtained with a second-generation system operated at room temperature and sub-Kelvin temperatures.
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Submitted 12 November, 2025; v1 submitted 9 April, 2025;
originally announced April 2025.
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Light Dark Matter Constraints from SuperCDMS HVeV Detectors Operated Underground with an Anticoincidence Event Selection
Authors:
SuperCDMS Collaboration,
M. F. Albakry,
I. Alkhatib,
D. Alonso-González,
D. W. P. Amaral,
J. Anczarski,
T. Aralis,
T. Aramaki,
I. J. Arnquist,
I. Ataee Langroudy,
E. Azadbakht,
C. Bathurst,
R. Bhattacharyya,
A. J. Biffl,
P. L. Brink,
M. Buchanan,
R. Bunker,
B. Cabrera,
R. Calkins,
R. A. Cameron,
C. Cartaro,
D. G. Cerdeño,
Y. -Y. Chang,
M. Chaudhuri,
J. -H. Chen
, et al. (117 additional authors not shown)
Abstract:
This article presents constraints on dark-matter-electron interactions obtained from the first underground data-taking campaign with multiple SuperCDMS HVeV detectors operated in the same housing. An exposure of 7.63 g-days is used to set upper limits on the dark-matter-electron scattering cross section for dark matter masses between 0.5 and 1000 MeV/$c^2$, as well as upper limits on dark photon k…
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This article presents constraints on dark-matter-electron interactions obtained from the first underground data-taking campaign with multiple SuperCDMS HVeV detectors operated in the same housing. An exposure of 7.63 g-days is used to set upper limits on the dark-matter-electron scattering cross section for dark matter masses between 0.5 and 1000 MeV/$c^2$, as well as upper limits on dark photon kinetic mixing and axion-like particle axioelectric coupling for masses between 1.2 and 23.3 eV/$c^2$. Compared to an earlier HVeV search, sensitivity was improved as a result of an increased overburden of 225 meters of water equivalent, an anticoincidence event selection, and better pile-up rejection. In the case of dark-matter-electron scattering via a heavy mediator, an improvement by up to a factor of 25 in cross-section sensitivity was achieved.
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Submitted 5 September, 2024; v1 submitted 10 July, 2024;
originally announced July 2024.
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Two-Stage Cryogenic HEMT Based Amplifier For Low Temperature Detectors
Authors:
J. Anczarski,
M. Dubovskov,
C. W. Fink,
S. Kevane,
N. A. Kurinsky,
A. Mazumdar,
S. J. Meijer,
A. Phipps,
F. Ronning,
I. Rydstrom,
A. Simchony,
Z. Smith,
S. M. Thomas,
S. L. Watkins,
B. A. Young
Abstract:
To search for dark matter candidates with masses below $\mathcal{O}$(MeV), the SPLENDOR (Search for Particles of Light dark mattEr with Narrow-gap semiconDuctORs) experiment is developing novel narrow-bandgap semiconductors with electronic bandgaps on the order of 1-100 meV. In order to detect the charge signal produced by scattering or absorption events, SPLENDOR has designed a two-stage cryogeni…
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To search for dark matter candidates with masses below $\mathcal{O}$(MeV), the SPLENDOR (Search for Particles of Light dark mattEr with Narrow-gap semiconDuctORs) experiment is developing novel narrow-bandgap semiconductors with electronic bandgaps on the order of 1-100 meV. In order to detect the charge signal produced by scattering or absorption events, SPLENDOR has designed a two-stage cryogenic HEMT-based amplifier with an estimated charge resolution approaching the single-electron level. A low-capacitance ($\sim$1.6 pF) HEMT is used as a buffer stage at $T=10\,\mathrm{mK}$ to mitigate effects of stray capacitance at the input. The buffered signal is then amplified by a higher-capacitance ($\sim$200 pF) HEMT amplifier stage at $T=4\,\mathrm{K}$. Importantly, the design of this amplifier makes it usable with any insulating material - allowing for rapid prototyping of a variety of novel detector materials. We present the two-stage cryogenic amplifier design, preliminary voltage noise performance, and estimated charge resolution of 7.2 electrons.
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Submitted 26 January, 2024; v1 submitted 3 November, 2023;
originally announced November 2023.
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Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
Authors:
J. C. Algaba,
J. Anczarski,
K. Asada,
M. Balokovic,
S. Chandra,
Y. -Z. Cui,
A. D. Falcone,
M. Giroletti,
C. Goddi,
K. Hada,
D. Haggard,
S. Jorstad,
A. Kaur,
T. Kawashima,
G. Keating,
J. -Y. Kim,
M. Kino,
S. Komossa,
E. V. Kravchenko,
T. P. Krichbaum,
S. -S. Lee,
R. -S. Lu,
M. Lucchini,
S. Markoff,
J. Neilsen
, et al. (14 additional authors not shown)
Abstract:
In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass approximately 6.5 x 10^9 M_solar. The EHTC also partnered with several international facilities in space and on the ground,…
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In 2017, the Event Horizon Telescope (EHT) Collaboration succeeded in capturing the first direct image of the center of the M87 galaxy. The asymmetric ring morphology and size are consistent with theoretical expectations for a weakly accreting supermassive black hole of mass approximately 6.5 x 10^9 M_solar. The EHTC also partnered with several international facilities in space and on the ground, to arrange an extensive, quasi-simultaneous multi-wavelength campaign. This Letter presents the results and analysis of this campaign, as well as the multi-wavelength data as a legacy data repository. We captured M87 in a historically low state, and the core flux dominates over HST-1 at high energies, making it possible to combine core flux constraints with the more spatially precise very long baseline interferometry data. We present the most complete simultaneous multi-wavelength spectrum of the active nucleus to date, and discuss the complexity and caveats of combining data from different spatial scales into one broadband spectrum. We apply two heuristic, isotropic leptonic single-zone models to provide insight into the basic source properties, but conclude that a structured jet is necessary to explain M87's spectrum. We can exclude that the simultaneous gamma-ray emission is produced via inverse Compton emission in the same region producing the EHT mm-band emission, and further conclude that the gamma-rays can only be produced in the inner jets (inward of HST-1) if there are strongly particle-dominated regions. Direct synchrotron emission from accelerated protons and secondaries cannot yet be excluded.
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Submitted 14 April, 2021;
originally announced April 2021.
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Low-Temperature and Dynamic Magnetism of Highly Frustrated 5d2 Li4MgOsO6 Polymorphs in Comparison with 5d3 Li3Mg2OsO6
Authors:
Gia T. Tran,
Phuong-Hieu T. Nguyen,
Charles J. Bloed,
Michael E. Evans,
Jamie A. Anczarski,
William P. Martin,
Jefferson Toro,
Demetrios V. Papakostas,
James Beare,
Murray N. Wilson,
John E. Greedan,
Graeme M. Luke,
Thomas Gredig,
Jeremy P. Carlo,
Shahab Derakhshan
Abstract:
Geometric magnetic frustration (GMF) has attracted substantial interest due to the exotic physics and rich phase diagrams revealed by the cancellation of normally-dominant magnetic interactions, giving impetus for the search for novel frustrated systems, most often based on antiferromagnetic correlations between magnetic ions decorating triangular or tetrahedral lattices. We report here low-temper…
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Geometric magnetic frustration (GMF) has attracted substantial interest due to the exotic physics and rich phase diagrams revealed by the cancellation of normally-dominant magnetic interactions, giving impetus for the search for novel frustrated systems, most often based on antiferromagnetic correlations between magnetic ions decorating triangular or tetrahedral lattices. We report here low-temperature magnetic susceptibility and muon spin relaxation results on Li4MgOsO6 and Li3Mg2OsO6, members of the A5BO6 "rock salt ordered" family of frustrated materials. In Li3Mg2OsO6 we find spin freezing below 12K. In Li4MgOsO6, which can crystallize into either orthorhombic Fddd or monoclinic C2/m crystal symmetries depending on synthesis conditions, we find magnetism consistent with glassy-like behavior dominating below 2K, with partial ordering and evidence for dynamics at somewhat higher temperatures.
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Submitted 1 November, 2018; v1 submitted 12 September, 2018;
originally announced September 2018.