Quantum Sensing for Fundamental Physics Workshop

2 Sept 2026, 09:30 → 4 Sept 2026, 17:00 Europe/Zurich

Amphithéâtre Hermite (Institut Henri Poincaré (IHP))

Jeanne Bally (LPENS), Chloé Fruy (LPENS), Takis Kontos (LPENS), Raffaele D'Agnolo (LPENS), Mariama Diallo (LPENS)

6th RADES Collaboration Meeting

poster_rades.pdf

Wednesday 2 September

1 Welcome and introduction

Speaker: Dr Takis Kontos (LPENS)

Session 1

Convener: Dr Takis Kontos (LPENS)

2 Non-relativistic unitarity, long-range interactions and dark matter

Speaker: Dr Kalliopi Petraki (LPENS)

PETRAKI_RADES_UnitarityLongRangeInteractions.pdf

3 Quantum sensing of axion dark matter and other cosmological signals

There is a general consensus that a large part of the matter and energy in the Universe is unknown. Well-established candidates for dark matter are axions or axion-like particles. While axions are expected, if they exist, to be everywhere in the galactic halo, their interaction with Standard Model particles is predicted to be very weak, and their mass (or frequency) is unknown. Hence, their detection requires broadband and ultrasensitive amplification and measurement techniques. Quantum sensing is appealing because it reaches the ultimate resolution, limited by the Heisenberg uncertainty principle. Pioneering experiments using quantum-limited microwave amplifiers based on superconducting circuit technology have explored the possibility of accelerating the axion dark-matter search. However, most of these experiments intrinsically rely on power measurements, which leads to a major limitation in the detection time. Furthermore, the standard microwave cavities used in these setups have limited frequency tunability, which restricts the accessible frequency range for axion detection. To overcome these limitations, we propose a paradigm for quantum-enhanced axion dark-matter search that does not rely on power measurements and offers wide frequency tunability. We propose to directly measure the axion amplitude and phase in an interferometric protocol at the quantum limit, using a nonlinear microwave cavity. In addition, we introduce gyromagnetic modes as wide-mass-range transducers for axion signals. We expect this scheme to offer an improvement of at least four orders of magnitude in the figure of merit and at least two orders of magnitude in mass (frequency) window with respect to standard haloscopes. Owing to its generality, our proposed protocol has the potential to speed up axion searches, as well as the detection for other cosmological signals such as the strongly red-shifted 21cm radiation from the early Universe. I will discuss the work done in Paris in this direction.

Speaker: Dr Audrey Cottet (LPENS)

CottetParis2026_3.pdf

11:00 Coffee Break

4 Axion Searches at the University of Manchester

I give a brief update on axion experiments at the University of Manchester. I will describe recent updates on cavity development, plans to construct a pathfinder experiment at 30GHz, as well as detailing recent successes on the development of quantum noise limited parametric amplifiers. Time permitting, I will also describe searches for high-frequency gravitational waves.

Speaker: Dr Jamie McDonald (University of Manchester)

Quantum_Sensing_Fund_Physics_Paris_2026.pdf

12:10 Lunch

(+poster installation)

Session 2

Convener: Jeanne Bally

5 GravNet: where we stand after one year

Speaker: Diego Blas (IFAE)

2Blas-compressed.pdf

6 Quantum sensing for the detection of dark matter axions with RADES: the DarkQuantum project

I will review the plans and status of the DarkQuantum project, which intends to develop several techniques to improve the performance of axion haloscopes, and implement it in several of the RADES setups. Most relevant the use of quantum sensing to improve effective noise figures close to, and beyond, the standard quantum limit.

Speaker: Dr Igor Irastorza (Unizar)

DarkQuantum_RADES_Paris_Irastorza_.pdf

DarkQuantum_RADES_Paris_Irastorza_.pptx

15:20 Coffee Break

7 Quantum Magnetometry In Search of Dark Matter

When bosonic Dark Matter (DM) has an ultra-light mass, it acts as a classical, coherent field. In many cases, and specifically for many models of axion-like-particles, this field has a magnetic-like effect on spins, and can therefore be measured by spin-based quantum magnetometers. In this seminar, I will explain the workings of quantum magnetometers, focusing on comagnetometers, which simultaneously utilize several species of atoms to achieve a variety of benefits. I will discuss my work on the self compensating comagnetometer, and spotlight my proposal for a new sensor called the RoW comag, which I plan to build in my up and coming lab. I will also discuss my work as one of the founding members of the Noble and Alkali Spin Detectors for Ultralight Coherent darK matter (NASDUCK) collaboration, which was formed a few years ago to measure DM with magnetometers. I will also touch upon my current involvement in multiple other spin-based magnetometry ideas, including ones that might one day connect to new directions such as measuring observables in colliders.

Speaker: Itay Bloch

RoWComag_2026_Paris.pdf

Poster Session

Conveners: Dr Chloé Fruy (LPENS), Jeanne Bally

Thursday 3 September

Session 3

Convener: Dr David Diez Ibanez (LPENS)

8 Atom interferometers as particle detectors

Atom interferometers are emerging as powerful probes of fundamental physics, with applications ranging from gravitational-wave detection to searches for ultra-light dark matter. In this talk, I will explore a complementary possibility: using atom interferometers as detectors of sub-GeV dark matter. Their extremely low effective energy threshold allows them to probe scattering processes that can be inaccessible to conventional recoil-based experiments. I will discuss how dark-matter scattering can leave an observable imprint on the macroscopic spatial superposition realized in an atom interferometer, through loss of contrast and phase shifts. Different observables become optimal depending on the spatial resolution and nature of the interaction. I will discuss the sensitivity of current and future atom interferometers to sub-GeV dark matter, the main parametric scalings controlling their reach, and possible directions for extending these ideas to other quantum sensing platforms.

Speaker: Clara Murgui Galvez (CERN)

Paris_RADES.pdf

9 Sensing with superconducting parametric amplifiers (closed session)

In recent years the field of circuit-QED has benefited from the emergence of superconducting parametric amplifiers - in particular, traveling wave parametric amplifiers (TWPAs) have become widely used in the qubit measurement chain. Here I will focus on a series of experiments realized at Aalto using the so-called Josephson parametric amplifiers (JPA). These devices have a rich phase diagram, presenting first and second order transitions that merge in a critical point. This phase diagram and the associated switching rates can be calculated theoretically by the use of effective potentials. I will show how this parametric criticality can be used for detection of single microwave photons. I will also present recent experiments where the JPA is used for generating squeezed states, which can be employed for below-SQL (standard quantum limit) detection of phases. References: K Petrovnin, J Wang, GS Paraoanu, Communications Physics 8, 378 (2025); J Wang, K Petrovnin, PJ Hakonen, GS Paraoanu, IEEE Transactions on Quantum Engineering 6, 3500208 (2025) K Petrovnin, J Wang, M Perelshtein, P Hakonen, GS Paraoanu, PRX Quantum 5, 020342 (2024); R Di Candia, F Minganti, KV Petrovnin, GS Paraoanu, S Felicetti, npj Quantum Information 9, 23 (2023).

Speaker: Dr Gheorghe-Sorin Paraoanu (Aalto University)

10:50 Coffee Break

10 Quantum Sensing with Superconducting Qubits

I will give an overview of the activity and perspectives for quantum sensing with superconducting qubits at LNF.

Speaker: Claudio Gatti

QS4FPWorkshop-Paris2026-CGatti.pdf

QS4FPWorkshop-Paris2026-CGatti.pdf

QS4FPWorkshop-Paris2026-CGatti.pptx

12:00 Lunch

CLOSED SESSION: Steering Committee

Convener: Dr Babette Döbrich (MPP)

Session 4

Convener: Mr Kenta Kodama (LPENS)

11 Inelasticity, Unitarity and Self-Interacting Dark Matter

Speaker: Thomas Pignard (LPENS)

QUANTUM_SENSING_PARIS_09_26.pdf

12 Single-Microwave-Photon Detection for Axion Searches at INFN-LNL

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 cavity mode.

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 conducted at LNL-INFN laboratories (Padova, Italy), with both hybrid systems and conventional axion-photon haloscopes over broader bands.

Speaker: Caterina Braggio (Università di Padova)

Braggio.pdf

15:20 Coffee Break

13 Powder haloscope

Speaker: Junwu Huang

14 Quantum heuristics for gravitational-wave detection: high-frequency sensitivity limits for current and near-future BSM searches

LIGO, VIRGO and Kagra (to name just a few) represent outstanding feats of engineering that have launched us in a new era of gravitational-wave (GW) detection. Even so, we may wonder whether their sensitivity is enough to detect very high-frequency signals of BSM origin, such as those sourced by primordial stochastic GW backgrounds. In this talk, I will argue that the sensitivity of present-day and near-future GW detectors will most likely prove insufficient in this regard. I will present the quantum mechanical framework in which this question can be properly addressed, and within which models of both operating and proposed GW detectors can be constructed. Using these models, I will present optimistic projections obtained by pushing these detectors to their quantum limit. This will allow us to ultimately establish the fundamental sensitivity limits of these detectors, showing that, even when operated at their quantum limit, they become blind to cosmologically allowed stochastic backgrounds before reaching frequencies of significant phenomenological interest.

Speaker: Paolo Bilisco (IPhT - Université Paris-Saclay)

BiliscoPaolo_Presentation.pdf

17:10 Lab Visit

19:30 Diner

Friday 4 September

Cavity Session

Convener: Dr Chloé Fruy (LPENS)

15 Towards a Tunable and Modular Qubit-Based Haloscope with Vertical-Cut Cavities

Superconducting qubits and microwave photon counting offer a promising route towards quantum-enhanced axion searches, but efficient frequency scanning over a broad range remains a major challenge. We investigate a modular haloscope architecture combining a fixed readout cavity and transmon-based detection with elongated storage cavities employing vertical-cut tuning. This approach enables frequency tuning without introducing large perturbing elements into the cavity volume, while an external shielding structure is investigated to mitigate photon leakage through the tuning gap. Long single-cavity and multicavity storage configurations are also explored to increase the resonant volume while controlling unwanted electromagnetic modes and maintaining suitable qubit–cavity coupling. The goal is to establish a tunable and modular architecture capable of combining broad frequency coverage with the electromagnetic and quantum performance required for future photon-counting axion searches.

Speaker: Dr Jose Maria Garcia Barcelo

Slides_QSFPW-6thRADESCM_JMGB.pdf

Slides_QSFPW-6thRADESCM_JMGB.pdf

Slides_QSFPW-6thRADESCM_JMGB.ppt

16 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

RADESsept2026_v2.pdf

17 Heterodyne detection applied to the RADES-BabyIAXO haloscopes

We study resonant heterodyne up-conversion in the RADES-BabyIAXO haloscope as a method to search for low-mass dark matter axions using microwave cavities. Starting from axion electrodynamics, we derive the axion-induced source term and the power extracted through a readout mode, explicitly accounting for the finite axion linewidth. This leads to effective quality factors that determine the pump-axion mixing, detection bandwidth, and detected signal power. We extend the BI-RME 3D full-wave formulation to heterodyne axion detection in a realistic two-port cavity, including pump leakage into the readout channel. Applying the formalism to the largest RADES-BabyIAXO cavity identifies the quasi-TE011−quasi-TM010 mode pair as a favorable configuration, enabling sensitivity to axion frequencies between 0.9 and 34.6 MHz. Analytical and full-wave predictions show excellent agreement at resonance, while the full-wave model provides a more accurate description off resonance and allows a precise characterization of the pump leakage. We also derive the optimal port couplings that maximize the scanning rate. Sensitivity projections for cryogenic copper and superconducting niobium cavities indicate that, under thermal-noise-limited conditions and assuming sufficient pump-leakage rejection, the experiment could probe axion-photon couplings down to 10−15GeV−1 at 90% confidence level, representing a significant improvement over previous heterodyne-based searches.

Speaker: Jose Ramón Navarro Madrid

upconversion_paris.pdf

upconversion_paris.pptx

18 Recent Progress in HTS REBCO Coatings for the RADES Haloscope

This report summarizes our recent progress on high-temperature superconducting (HTS) REBCO coatings for the RADES axion dark matter search. We present an optimized coating procedure based on a delamination technique that exposes the superconducting layer directly to the RF field, improving the cavity quality factor.To assess the mechanical reliability of the coating, we carried out adhesion pull-off tests and pressure sensitive film measurements to evaluate the pressure distribution within the cavity. We also present a dedicated testing insert currently under development at ICMAB. Once completed, this setup will allow us to characterize the performance of the HTS coatings under high magnetic fields, helping us optimize our coating techniques for future RADES cavities.

Speaker: Irfan Ahmed (ICMAB-CSIC)

6th RADES Collaboration Meeting (IHP)..pdf

10:50 Coffee Break

Detection Session

Conveners: Dr Jose Maria Garcia Barcelo (Unizar), Dr Jose Ramon Navarro Madrid (UPCT)

19 Benchmarking Dark Matter Search using a Parity-Check Protocol with Machine-Learning Optimized Pulses

We report on an improved microwave detection protocol for dark matter candidates such as the axion and the dark photon. We employ a superconducting transmon qubit dispersively coupled to a double-cavity system, enabling quantum non-demolition measurements of the photon occupation in a relatively short-lived storage cavity. To reduce the experimental cycle time and enhance sensitivity for axion and dark-photon searches, we operate this detector in a regime of increased qubit-cavity coupling, resulting in Stark shifts of 4.6 MHz. In this regime, conventional control pulses suffer from strong frequency-detuning sensitivity and photon-number-dependent errors. We address this limitation by implementing frequency-detuning-robust π/2 pulses (obtained by machine-learning optimization) that preserve high-fidelity qubit control over a bandwidth of approximately 20 MHz. We experimentally validate this protocol and demonstrate single-photon detection performance comparable to previous implementations, despite significantly reduced qubit coherence times and storage-cavity lifetimes. Using parity-based measurement sequences combined with a Hidden Markov Model (HMM) analysis, we achieve background rates on the order of O(20) Hz. In the absence of a magnetic field, we derive exclusion limits on the dark photon model for dark matter, reaching a sensitivity to the kinetic mixing angle of ε95%∼1×10−14 at 5.051 GHz. These results establish machine-learning robust control as a key enabler for faster, more scalable microwave quantum sensors for dark-matter searches.

Speaker: Marko Kuzmanović

Kuzmanovic_RADES_SEPT_2026.pdf

20 Superconducting nitridized aluminum resonators

Nitridized aluminum (NitrAl, for short), a superconducting form of nitrogen-doped aluminum, is a promising material for quantum circuit applications. Its critical temperature is enhanced in comparison to pure aluminum, it has shown resilience to magnetic fields in the order of Tesla and its kinetic inductance has been estimated to lie in the range of superinducting disordered materials. Due to all these reasons, this material has great potential for the manufacturing of qubits intended to be used in the QRADES experiment. Nonetheless, the factual value of the kinetic inductance of the material and an estimation of its losses still remain an unknown. In IFAE, we have shed some light into those aspects by the fabrication and measurement of superconducting resonators. We have developed recipes for patterning NitrAl circuits in different resistivity regimes, developed dedicated designs of resonant structures and conducted single-photon and multi-photon measurements of them, alongside temperature and power sweeps. In this talk, I will be presenting the results concerning those measurements and the conclusions that arise from the observed data and trends.

Speaker: Ariadna Gómez del Pulgar Martínez

Superconducting nitridized aluminum resonators_compressed.pdf

Superconducting nitridized aluminum resonators.pdf

12:00 Lunch

Detection Session: CLOSED SESSION

21 Single photon detection with transmons for axion experiments: a reanalysis of the Dixit et al. experiment

Superconducting transmons are a promising technology to increase the sensitivity of single photon detection. In this talk I present a reanalysis of the data of the first experiment by Dixit et al. (2021) for a dark photon search with transmons. This points to the technical progress that is needed to reduce the noise, caused not only by spontaneous creation of photons in the cavity but by undesired couplings with the qubit measurement process.

Speaker: Jordi Miralda

Paris_26.pdf

22 Status of the qubit measurement in a cylindrical cavity with the QICK system (closed session)

We will discuss the qubit measurement with the new bluefors system in CAPA, University of Zaragoza. In those measurements, we managed to work with the Quantum Instrumentation Control Kit (QICK), it is an FPGA system and comparing with the other commercial products for the qubit manipulation, it has a similar performance but much less cost. This is also a new test for the cylindrical cavity with the transmon.

Speakers: Mina Yami, Yikun Gu (University of Zaragoza)

23 Numerical Optimization of Fluxonium Based Single Microwave Photon Detector

Single microwave photon detectors (SMPDs) are key components for quantum technologies, including quantum communication, quantum sensing (e.g., axion searches), and the readout of weak microwave signals in superconducting quantum circuits. In this work, we present the design of a superconducting-qubit-based SMPD with the long-term goal of achieving operation in high magnetic fields. Our approach builds on the magnetic-field resilience demonstrated by the granular-aluminum (grAl) fluxonium developed in our group, which has demonstrated operation in in-plane magnetic fields up to 1.2 T. As a proof of concept, we investigate a fluxonium-based detector coupled to two microwave resonators, enabling the conversion of an incoming microwave photon into a measurable qubit excitation through a four-wave mixing (4WM) process. Achieving a sufficiently high conversion rate requires careful optimization of the circuit parameters. To this end, we performed an extensive numerical investigation combining an initial parameter-space filtering, evaluation of the relevant transition matrix elements, and Floquet simulations to identify operating regions with suppressed unwanted transitions. This optimization procedure led to two promising fluxonium designs, operating at zero-flux and half-flux bias, respectively, each providing three suitable operating points for efficient photon conversion. These results establish the foundations for the realization of a magnetic-field-resilient SMPD based on the fluxonium architecture and provide practical design guidelines for its experimental implementation.

Speaker: Danilo Angelone (Karlsruhe Institute of Technology)

Rades Collab. Meeting 2026.pptx

15:00 Coffee Break

Analysis Session: CLOSED SESSION

Convener: Dr Takis Kontos (LPENS)

24 RADES data management and pre-processing with REST-for-Physics' Halolib Library (closed session)

The REST-for-Physics (Rare Event Searches Toolkit) Framework is mainly written in C++ and is fully integrated with ROOT I/O interface. REST was initially born as a collaborative software effort to provide common tools for acquisition, simulation, and data analysis of gaseous time projection chambers. However, the framework is already extending its usage to be non-exclusive of detector data analysis.

The Halolib library is being written for the REST framework as a method for managing and early processing of cavity haloscope power spectrum data. Using RADES SM18 data as a template, Halolib supports power spectra event type and their metadata for ease of accessibility and traceability throughout the collaboration. The library also supports basic pre-processing techniques like trimming of off-resonance tail frequencies and combination of spectra by their weighted mean.

Speaker: Sophia Jane Hollick (Universidad de Zaragoza)

25 Status of the SM18 data analysis and preliminary results (closed session)

I will present the status of the ongoing analysis. Currently we have obtained preliminary results for the period where the cavity temperature was kept fixed. I will also discuss the data from the period where the resonant frequency was tuned by varying the temperature of the helium bath and the current approach to extend the analysis to it.

Speaker: Cristian Cogollos Trivino (Max Planck Institute for Physics (DE))

26 The DQLF receiver chain (closed session)

I will be presenting the status of the DQLF receiver chain and the progress made in the last six months. This includes a first characterizations of the SQUID-based read-out, a first mock dark photon run at room temperature using an automated protocol, and a new idea to measure the strong port coupling without a reflection measurement.

Speaker: Jacob Mathias Egge