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Samuel Berweger

Publications and source records attributed to Samuel Berweger.

At least 19 recordsLinked to original sources
arXiv2026

Super-Resolution Experimental Validation and Polarimetric Extension of the Effective Roughness Diffuse Scattering Models

The experimental validation of diffuse scattering models has long been limited by the inability to spatially separate specular and diffuse contributions in measured channels. This paper overcomes this limitation by combining super-resolution multipath component (MPC) extraction, which resolves individual propagation paths including the specular component, with digital-twin-assisted geometry, enabling the spatial separation of specular and diffuse contributions from bistatic measurements at 28~GHz. Using this framework, we provide the first measurement-driven validation of the Effective Roughness (ER) model with independent characterization of diffuse scattering across ten common building materials, each measured over 266 angular configurations and all polarization combinations (HH, HV, VH, VV). Furthermore, we extend the ER framework by proposing a novel angle-dependent cross-polarization discrimination (XPD) model, capturing the geometry-dependent nature of depolarization that is neglected in existing approaches. The proposed method reproduces the measured diffuse power trends, achieving RMSE values as low as 3 dB across the tested materials, and improves XPD prediction over the baseline constant-XPD model for nearly all material-polarization cases. These results establish a physically consistent and practically viable approach for high-fidelity channel modeling in mmWave systems.

eess.SP↗
arXiv2026

A Computationally Efficient Reciprocal Effective Roughness Model for Diffuse Scattering

Ray-tracing (RT) has become central to site-specific electromagnetic propagation modeling in dynamic complex environments. Yet its computational burden grows sharply as high-fidelity digital twins of these environments scale to millions of facets whose material parameters must be continuously updated as the environment changes. The challenge is amplified at mmWave and sub-THz frequencies, where surface roughness becomes comparable to the wavelength and so diffuse scattering can account for up to 40% of the received power, making accurate yet tractable models essential. The popular Effective Roughness (ER) approach offers physical consistency but become increasingly costly when highly directive lobes are required or when parameters must be iteratively tuned. This communication introduces a directive, reciprocal diffuse scattering model that preserves the structure of the ER while enabling an order-of-magnitude reduction in computational cost. Validation across eight materials shows no loss in accuracy - and a slight improvement - demonstrating a scalable and physically meaningful solution for RT in scenarios where diffuse scattering is non-negligible.

eess.SP↗
arXiv2026

Semantically Annotated Multimodal Dataset for RF Interpretation and Prediction

Current limitations in wireless modeling and radio frequency (RF)-based AI are primarily driven by a lack of high-quality, measurement-based datasets that connect RF signals to their physical environments. RF heatmaps, the typical form of such data, are high-dimensional and complex but lack the geometric and semantic context needed for interpretation, constraining the development of supervised machine learning models. To address this bottleneck, we propose a new class of multimodal datasets that combines RF measurements with auxiliary modalities like high-resolution cameras and lidar to bridge the gap between RF signals and their physical causes. The proposed data collection will span diverse indoor and outdoor environments, featuring both static and dynamic scenarios, including human activities ranging from walking to subtle gestures. By achieving precise spatial and temporal co-registration and creating digital replicas for voxel-level annotation, this dataset will enable transformative AI research. Key tasks include the forward problem of predicting RF heatmaps from visual data to revolutionize wireless system design, and the inverse problem of inferring scene semantics from RF signals, creating a new form of RF-based perception.

cs.ET↗
arXiv2026

MHz to sub-kHz field detection with an all-dielectric potassium Rydberg-atom sensor

Rydberg sensors have significant promise as an alternative to the antenna systems used for sub-MHz frequency communications, where the scale of high-efficiency antennas is often impractically large, forcing the use of low-efficiency, electrically small antennas. The exploration of Rydberg sensors at these frequencies has been hampered by the low field transmission of the silicate vapor cells. We dramatically improve the low-frequency field transmission of silicate vapor cells by using potassium as the active medium instead of rubidium or cesium. The potassium Rydberg sensor can measure fields with frequencies down to 500 Hz in an all-dielectric sensor, effectively extending the low-frequency cutoff of the sensor by nearly four orders of magnitude compared to an equivalent rubidium vapor cell. With this simple substitution, experimentation with low-frequency sensing becomes dramatically more accessible to the community.

physics.atom-ph↗
arXiv2026

Fundamental linewidth limit of electromagnetically induced transparency in a thermal Rydberg ladder

Spectroscopy of Rydberg states has become a popular platform for quantum sensing, with the most common readout scheme being two-photon electromagnetically induced transparency (EIT) using counter-propagating laser beams. In this scheme, the energy resolution of the Rydberg state is set by the spectral linewidth of the EIT feature. While selection criteria for the two-photon resonance can narrow the linewidth to the order of the Rydberg state decay rate for a single atom, the Doppler shift from thermal velocity of the atoms broadens the ensemble linewidth to the order of the decay rate of the intermediate state. Here, we derive an analytic expression for the Doppler residual lineshape in the low-power limit and corroborate the results with experiment. For Rb, we find the full-width at half-maximum linewidth limit to be 1.84 MHz when scanning the coupling laser and measure an experimental linewidth of 2.04 MHz. These linewidths are around a factor of two narrower than previous theoretical estimates as well as previously reported measured linewidths. With this, we demonstrate the most precise two-photon energy resolution of a Rydberg state in thermal vapor to date. We then map out broadening mechanisms near this limit.

physics.atom-ph↗
arXiv2026

Simultaneous Detection, Demodulation, and Angle-of-Arrival Determination of Communication Signals Using a Dual Ladder Rydberg Receiver

In a typical Rydberg mixer, modulated communication signals are detected using a radio frequency (RF) heterodyne technique. The mixer outputs an intermediate frequency (IF), which must be filtered and mixed down to baseband. In this work, we apply an RF-homodyne technique to demonstrate simultaneous detection and a direct, baseband readout of the in-phase (I) and quadrature (Q) components of standard communication signals using a dual ladder Rydberg receiver. We further show that the inherent polarization sensitivity of this receiver can be used to determine the signal's angle of arrival. We also compare the dual ladder system with a typical Rydberg mixer. The RF-heterodyne-based system's maximum detectable symbol rate is constrained by a signal amplitude which decays with the heterodyne field's detuning from the Rydberg-Rydberg atomic transition used to detect the signal, but the dual ladder design is not subject to this limitation. However, the dual ladder system is more sensitive to low-frequency noise. As a result, its performance is degraded relative to its conventional counterpart when subjected to pink noise. We show that once pink noise effects have been accounted for, both systems behave comparably.

physics.atom-ph↗
arXiv2025

Probing Bandwidth and Sensitivity in Rydberg Atom Sensing via Optical Homodyne and RF Heterodyne Detection

Rydberg atom based sensors allow for SI traceable measurements and show promise for applications in the field of communication and radar technologies. In this article, we investigate the bandwidth and sensitivity of a Rydberg atom-based sensor in a rubidium vapor cell using Rydberg electromagnetically induced transparency (EIT) spectroscopy. We employ a radio-frequency (RF) heterodyne measurement technique in combination with an optical homodyne setup to extend the achievable range between sensitivity and bandwidth in a Rydberg sensor. While the bandwidth of Rydberg sensors are limited by the transit time of atoms and the Rabi frequency of the coupling field, achieving higher bandwidth through smaller beam sizes is thought to compromise sensitivity due to reduced EIT signal strength. Using optical homodyne detection, we demonstrate that sensitivity is preserved while achieving a response bandwidth of 8 MHz. In addition, using the Rydberg sensor, we receive digital communication signals and present error vector magnitude (EVM) measurements as a function of varying symbol rates and bandwidth of the Rydberg sensor. Furthermore, the sensor's performance is compared with a conventional RF mixer. We establish that the bandwidth of a Rydberg sensor when receiving a pure tone is not the same as the bandwidth of the sensor when receiving a modulated signal. This difference results from the spreading of symbols in the frequency domain, leading to a reduction of the signal to noise ratio (SNR) and an accumulation of noise over the total span of the modulated signal.

quant-ph↗
arXiv2025

Sensitivity Comparison of Rydberg Atom-Based Radio-Frequency Electric Field Detection: Ionization Current Versus Optical Readout

We investigate a technique for detecting radio-frequency (RF) electric fields in a Cesium (Cs) vapor cell at room temperature by collecting charge from ionized Rydberg atoms and compare its performance with the established method of electromagnetically induced transparency (EIT). By applying a known RF field, we measure the response from both the electrical (ionization current-based) and optical (EIT-based) readouts. The ionization current-based method yields a sensitivity of 22~$\mu$Vm$^{-1}$Hz$^{-1/2}$, while the EIT-based method achieves 3.7~$\mu$Vm$^{-1}$Hz$^{-1/2}$. The sensitivity of the ionization current-based method is limited by thermal noise arising from a 2.2~k$\Omega$ resistance between the collection electrodes, attributed to a thin Cs film on the inner surfaces of the vapor cell. Controlling or eliminating the Cs layer can significantly improve the sensitivity of this ionization approach.

physics.atom-ph↗
arXiv2025

Deep Learning-based Human Gesture Channel Modeling for Integrated Sensing and Communication Scenarios

With the development of Integrated Sensing and Communication (ISAC) for Sixth-Generation (6G) wireless systems, contactless human recognition has emerged as one of the key application scenarios. Since human gesture motion induces subtle and random variations in wireless multipath propagation, how to accurately model human gesture channels has become a crucial issue for the design and validation of ISAC systems. To this end, this paper proposes a deep learning-based human gesture channel modeling framework for ISAC scenarios, in which the human body is decomposed into multiple body parts, and the mapping between human gestures and their corresponding multipath characteristics is learned from real-world measurements. Specifically, a Poisson neural network is employed to predict the number of Multi-Path Components (MPCs) for each human body part, while Conditional Variational Auto-Encoders (C-VAEs) are reused to generate the scattering points, which are further used to reconstruct continuous channel impulse responses and micro-Doppler signatures. Simulation results demonstrate that the proposed method achieves high accuracy and generalization across different gestures and subjects, providing an interpretable approach for data augmentation and the evaluation of gesture-based ISAC systems.

eess.SP↗
arXiv2025

An Imaging Radar Using a Rydberg Atom Receiver

Rydberg atoms in a gas form are highly sensitive electric field probes capable of detecting and measuring the amplitude, phase, and polarization of broadband time-varying signals. Here, we present the performance of a frequency modulated continuous wave (FMCW) radar using a Rydberg atom-based subwavelength sensor as a receiver. This sensor down converts the radar echoes, eliminates key FMCW electrical components, and performs two-dimensional target localization. To demonstrate its capabilities, we present an RF image of a scene containing targets in an anechoic room with radar cross sections down to 0 dBsm at a distance up to 5 m and with a range resolution of 4.7 cm.

physics.atom-ph↗
arXiv2025

Imaging of induced surface charge distribution effects in glass vapor cells used for Rydberg atom-based sensors

We demonstrate the imaging of localized surface electric (E) field effects on the atomic spectrum in a vapor cell used in Rydberg atom-based sensors. These surface E-fields can result from an induced electric charge distribution on the surface. Induced surface charge distributions can dramatically perturb the atomic spectrum, hence degrading the ability to perform electrometry. These effects become pronounced near the walls of the vapor cell, posing challenges for vapor cell miniaturization. Using a fluorescence imaging technique, we investigate the effects of surface charge on the atomic spectrum generated with electromagnetically induced transparency (EIT). Our results reveal that visible light (480 nm and 511 nm), i.e., the coupling laser used in two-photon Rydberg EIT schemes, generates localized patches of charge or dipoles where this light interacts with the glass walls of the vapor cell, while a three-photon Rydberg EIT scheme using only near-infrared wavelength lasers shows no measurable field induction. Additionally, imaging in a vacuum chamber where a glass plate is placed between large electrodes confirms that the induced charge is positive. We further validate these findings by studying the photoelectric effect with broadband light during EIT and impedance measurements. These results demonstrate the power of the fluorescence imaging technique to study localized E-field distributions in vapor cells and to target the photoelectric effect of the alkali-exposed glass of vapor cells as a major disruptor in Rydberg atom-based sensors.

physics.atom-ph↗
arXiv2024

RF-3DGS: Wireless Channel Modeling with Radio Radiance Field and 3D Gaussian Splatting

Precisely modeling radio propagation in complex environments has been a significant challenge, especially with the advent of 5G and beyond networks, where managing massive antenna arrays demands more detailed information. Traditional methods, such as empirical models and ray tracing, often fall short, either due to insufficient details or because of challenges for real-time applications. Inspired by the newly proposed 3D Gaussian Splatting method in the computer vision domain, which outperforms other methods in reconstructing optical radiance fields, we propose RF-3DGS, a novel approach that enables precise site-specific reconstruction of radio radiance fields from sparse samples. RF-3DGS can render radio spatial spectra at arbitrary positions within 2 ms following a brief 3-minute training period, effectively identifying dominant propagation paths. Furthermore, RF-3DGS can provide fine-grained Spatial Channel State Information (Spatial-CSI) of these paths, including the channel gain, the delay, the angle of arrival (AoA), and the angle of departure (AoD). Our experiments, calibrated through real-world measurements, demonstrate that RF-3DGS not only significantly improves reconstruction quality, training efficiency, and rendering speed compared to state-of-the-art methods, but also holds great potential for supporting wireless communication and advanced applications such as Integrated Sensing and Communication (ISAC). Code and dataset will be available at https://github.com/SunLab-UGA/RF-3DGS.

cs.NI↗
arXiv2024

Primary quantum thermometry of mm-wave blackbody radiation via induced state transfer in Rydberg states of cold atoms

Rydberg states of alkali atoms are highly sensitive to electromagnetic radiation in the GHz-to-THz regime because their transitions have large electric dipole moments. Consequently, environmental blackbody radiation (BBR) can couple Rydberg states together at $\mu$s timescales. Here, we track the BBR-induced transfer of a prepared Rydberg state to its neighbors and use the evolution of these state populations to characterize the BBR field at the relevant wavelengths, primarily at 130 GHz. We use selective field ionization readout of Rydberg states with principal quantum number $n\sim30$ in $^{85}$Rb and substantiate our ionization signal with a theoretical model. With this detection method, we measure the associated blackbody-radiation-induced time dynamics of these states, reproduce the results with a simple semi-classical population transfer model, and demonstrate that this measurement is temperature sensitive with a statistical sensitivity to the fractional temperature uncertainty of 0.09 Hz$^{-1/2}$, corresponding to 26 K$\cdot$Hz$^{-1/2}$ at room temperature. This represents a calibration-free SI-traceable temperature measurement, for which we calculate a systematic fractional temperature uncertainty of 0.006, corresponding to 2 K at room temperature when used as a primary temperature standard.

physics.atom-ph↗
arXiv2024

Observation of Asymmetric Sideband Generation in Strongly-driven Rydberg Atoms

Improving the bandwidth of Rydberg atom-based receivers is an ongoing challenge owing to the long-lived Rydberg state lifetimes that limit the refresh rate of ground state atoms. In particular, the LO-based Rydberg mixer approach allows for bandwidths into the few-MHz range. Here, we use heterodyne detection of the Rydberg atom receiver probe laser to separate the negative and positive sidebands that originate from distinct six wave mixing processes, in order to investigate their individual bandwidths. We experimentally confirm the prediction that the negative sideband exhibits a higher bandwidth than the positive sideband. We further explore the effect of coupling and probe laser Rabi frequency on the bandwidth, which we find to be in good agreement with our model. We achieved a maximum experimental (and theoretical) bandwidth of about 11 (11) MHz and 3.5 (5) MHz for the negative and positive sidebands, respectively, from the -3dB roll-off point for optimized field parameters. This work provides insight into the bandwidth-limiting features of Rydberg atom receivers and points the way towards further optimization of their response.

physics.atom-ph↗
arXiv2024

Independent Rydberg Atom Sensing using a Dual-Ladder Scheme

Rydberg atom-based electric field sensing can provide all-optical readout of radio frequency fields in a dielectric environment. However, because a single set of optical fields is typically used to prepare the Rydberg state and read out its response to RF fields, it is challenging to perform simultaneous and independent measurements of the RF field(s). Here we show that using two independent schemes to prepare and read out the same Rydberg state can be used to perform independent measurements in general, which we demonstrate specifically by resolving the the RF polarization. We expect this work will be useful for fiber-coupled sensor heads where spatial multiplexing is challenging, as well as for complex multi-level sensing schemes.

physics.atom-ph↗
arXiv2024

Investigation of fluorescence versus transmission readout for three-photon Rydberg excitation used in electrometry

We present a three-photon based fluorescence readout method where the strength of the fluorescence scales with the strength of the radio-frequency (RF) field being applied. We compare this method to conventional three-photon electromagnetically-induced transparency (EIT) and electromagnetically-induced absorption (EIA). Our demonstrated EIA/EIT sensitivity in the collinear three-photon Cesium system is the best reported to date at roughly 30 uVm^{-1}Hz^{-1/2}. The fluorescence is nearly 4 fold better in sensitivity compared to EIA/EIT readout.

quant-ph↗
arXiv2023

Zeeman-resolved Autler-Townes splitting in Rydberg atoms with tunable resonances and a single transition dipole moment

Applying a magnetic field as a method for tuning the frequency of Autler-Townes splitting for Rydberg electrometry has recently been demonstrated. In this paper we provide a theoretical understanding of EIT signals in the presence of a large magnetic field, as well as demonstrate some advantages of this technique over traditional Autler-Townes based electrometry. We show that a strong magnetic field provides a well-defined quantization axis regardless of the optical field polarizations, we demonstrate that by separating the $m_J$ levels of the Rydberg state we can perform an Autler-Townes splitting with a single participating dipole moment, and we demonstrate recovery of signal strength by populating a single $m_J$ level using circularly polarized light.

physics.atom-ph↗