arXiv subjects

Thomas Juffmann

Publications and source records attributed to Thomas Juffmann.

At least 19 recordsLinked to original sources

arXiv2026

Coupling free electrons to a trapped-ion quantum computer

Freely propagating electrons may serve as quantum probes that can become coherently correlated with other quantum systems, offering access to advanced metrological resources. We propose a setup that coherently couples free electrons in an electron microscope to a trapped-ion quantum processor, enabling non-destructive, quantum-coherent detection and the accumulation of information across multiple electrons. Our analysis shows that single electrons can induce resolvable qubit excitations, establishing a platform for practical applications such as quantum-enhanced, dose-efficient electron microscopy.

quant-ph↗

arXiv2025

Super-resolution Optical Near-field EM for bio- and materials science

Microscopy has been key to tremendous advances in science, technology, and medicine, revealing structure and dynamics across time and length scales. However, combining high spatial and temporal resolution in a non-invasive, label-free imaging technique remains a central challenge in microscopy. Here, we introduce Optical Near-field Electron Microscopy (ONEM), a method that converts optical near-field intensity patterns into photoelectron emission, enabling nanometer-scale imaging using low-energy electron microscopy. ONEM achieves 31 nm spatial and sub-second temporal resolution without exposing the sample to electrons, preserving structural and functional integrity. We demonstrate ONEM across three distinct domains: imaging polarization-dependent plasmon modes in metal nanostructures; visualizing live Escherichia coli in liquid with orientation-resolved contrast in 3D; and capturing real-time electrodeposition of copper nanoclusters from solution. These results establish ONEM as a versatile platform for damage-free super-resolution imaging of interface dynamics in both vacuum and liquid, with broad implications for biology, electrochemistry, and nanophotonics.

physics.optics↗

arXiv2025

Low-energy single-electron detector with sub-micron resolution

Single-electron detectors are a key component of electron microscopes and advanced electron optics experiments. We present a YAG:Ce scintillator-based single-electron detector with a spatial resolution of 1 micrometer at an electron energy of 17 keV. Single-electron detection events are identified with an efficiency and purity larger than 0.8 at an electron energy of 17 keV, reaching 0.96 at 30 keV. We show that the detector enables electron diffraction studies with a sample-detector distance comparable to the mean free path of electrons at atmospheric pressure, potentially enabling atmospheric electron diffraction studies.

physics.ins-det↗

arXiv2025

When Higher Resolution Reduces Precision: Quantum Limits of Off-Axis Interferometric Scattering Microscopy

Coherent interferometric scattering microscopy (iscat) enables nanoparticle tracking on microsecond timescales and with nanometer precision, and has become a key tool in structural and cellular biophysics. The achievable localization precision in such experiments is fundamentally limited by photon shot noise. Here, we analyze three-dimensional localization precision under oblique illumination in iscat using the framework of (Quantum) Fisher Information. We show that tilting the illumination can enhance localization precision and accuracy per detected photon, while increasing robustness to defocusing. Surprisingly, rotating coherent scattering microscopy (rocs), which incoherently averages oblique illuminations, achieves higher spatial resolution but lower localization precision. Our results establish the quantum limits of off-axis interferometric imaging and reveal that resolution and precision can behave in opposite ways -- a key insight for designing next-generation coherent microscopes.

physics.optics↗

arXiv2025

Super-resolution Live-cell Fluorescence Lifetime Imaging

Super-resolution Structured Illumination Microscopy (SR-SIM) enables fluorescence microscopy beyond the diffraction limit at high frame rates. Compared to other super-resolution microscopy techniques, the low photon fluence used in SR-SIM makes it readily compatible with live-cell imaging. Here, we combine SR-SIM with electro-optic fluorescence lifetime imaging (EOFLIM), adding the capability of monitoring physicochemical parameters with 156 nm spatial resolution at high frame rate for live-cell imaging. We demonstrate that our new SIMFLIM technique enables super-resolved multiplexed imaging of spectrally overlapping fluorophores, environmental sensing, and live-cell imaging.

physics.optics↗

arXiv2025

Laser-based aberration corrector

Aberration correctors are essential elements for achieving atomic resolution in state-of-the-art electron microscopes. Conventional correctors are based on a series of multipolar electron lenses, but more versatile alternatives are intensively sought. Here we suggest spatially tailored intense laser pulses as one such alternative. Our simulations demonstrate that the free-space electron-photon interaction can be used to compensate for spherical and chromatic aberrations of subsequent electron lenses. We show a significant improvement in the simulated electron probe sizes and discuss the prospects of utilizing the tailored laser fields as a platform for novel electron optics in ultrafast electron microscope setups.

physics.optics↗

arXiv2024

Cavity-enhanced continuous-wave microscopy using unstabilized cavities

Microscopy gives access to spatially resolved dynamics in different systems, from biological cells to cold atoms. A big challenge is maximizing the information per used probe particle to limit the damage to the probed system. We present a cavity-enhanced continuous-wave microscopy approach that provides enhanced signal-to-noise ratios at fixed damage. Employing a self-imaging 4f cavity, we show contrast enhancement for controlled test samples as well as biological samples. For thick samples, the imaging cavity leads to a new form of dark-field microscopy, where the separation of scattered and unscattered light is based on optical path length. We theoretically show that enhanced signal, signal-to-noise, and signal-to-noise per damage are also retrieved when the cavity cannot be stabilized. Our results provide an approach to cavity-enhanced microscopy with unstabilized cavities and might be used to enhance the performance of dispersive imaging of ultracold atoms.

physics.optics↗

arXiv2024

A Snapshot of Relativistic Motion: Visualizing the Terrell Effect

We present an experimental visualization of the Terrell effect, an optical phenomenon predicted in 1959 by Roger Penrose and James Terrell, which reveals that the Lorentz contraction of a moving object is not visible in a snapshot photograph. Using fs-laser pulses and a gated intensified camera that allows gating times as short as 300 ps, we achieve a virtual reduction of the speed of light to less than 2 m/s, enabling the visualisation of relativistically moving objects in real time. By capturing light reflected from deliberately Lorentz-contracted objects, our setup effectively reconstructs their visual appearance. This didactic visualization not only commemorates the centennial of Anton Lampa's seminal 1924 paper on relativistic length contraction but also provides the first experimental evidence of the Terrell effect in a laboratory setup. Our results comprise detailed relativistic illustrations, simulations and photographic snapshots of a sphere and a cube, which are animated to velocities close to the speed of light, revealing the apparent rotation effect and the distortion predicted by relativistic theory.

physics.optics↗

arXiv2024

Unified simulation platform for interference microscopy

Interferometric scattering microscopy is a powerful technique that enables various applications, such as mass photometry and particle tracking. Here we present a numerical toolbox to simulate images obtained in interferometric scattering, coherent bright-field, and dark-field microscopy. The scattered fields are calculated using a boundary element method, facilitating the simulation of arbitrary sample geometries and substrate layer structures. A fully vectorial model is used for simulating the imaging setup. We demonstrate excellent agreement between our simulations and experiments for different shapes of scatterers and excitation angles. Notably, for angles near the Brewster angle, we observe a contrast enhancement which may be beneficial for nanosensing applications. The software is available as a Matlab toolbox.

physics.optics↗

arXiv2023

Quantum Limits of Position and Polarizability Estimation in the Optical Near Field

Optical near fields are at the heart of various applications in sensing and imaging. We investigate dipole scattering as a parameter estimation problem and show that optical near-fields carry more information about the location and the polarizability of the scatterer than the respective far fields. This increase in information originates from and occurs simultaneously with the scattering process itself. Our calculations also yield the far-field localization limit for dipoles in free space.

quant-ph↗

arXiv2022

Transverse Electron Beam Shaping with Light

Interfacing electrons and light enables ultrafast electron microscopy, quantum control of electrons, as well as new optical elements for high sensitivity imaging. Here we demonstrate for the first time programmable transverse electron beam shaping in free space based on ponderomotive potentials from short intense laser pulses. We can realize both convex and concave electron lenses with a focal length of a few millimeters, comparable to those in state-of-the-art electron microscopes. We further show that we can realize almost arbitrary deflection patterns by shaping the ponderomotive potentials using a spatial light modulator. Our modulator is lossless, programmable, has unity fill factor, and could pave the way to electron wavefront shaping with hundreds of individually addressable pixels.

physics.optics↗

arXiv2021

Fundamental bounds on the precision of iSCAT, COBRI and dark-field microscopy for 3D localization and mass photometry

Interferometric imaging is an emerging technique for particle tracking and mass photometry. Mass or position are estimated from weak signals, coherently scattered from nanoparticles or single molecules, and interfered with a co-propagating reference. In this work, we perform a statistical analysis and derive lower bounds on the measurement precision of the parameters of interest from shot-noise limited images. This is done by computing the classical Cram\'er-Rao bound for localization and mass estimation, using a precise vectorial model of interferometric imaging techniques. We then derive fundamental bounds valid for any imaging system, based on the quantum Cram\'er-Rao formalism. This approach enables a rigorous and quantitative comparison of common techniques such as interferometric scattering microscopy (iSCAT), Coherent Brightfield microscopy (COBRI), and dark-field microscopy. In particular, we demonstrate that the light collection geometry in iSCAT greatly increases the axial position sensitivity, and that the Quantum Cram\'er-Rao bound for mass estimation yields a minimum relative estimation error of $\sigma_m/m=1/(2\sqrt{N})$, where $N$ is the number of collected scattered photons.

physics.optics↗

arXiv2021

Optical Near-Field Electron Microscopy

Imaging dynamical processes at interfaces and on the nanoscale is of great importance throughout science and technology. While light-optical imaging techniques often cannot provide the necessary spatial resolution, electron-optical techniques damage the specimen and cause dose-induced artefacts. Here, Optical Near-field Electron Microscopy (ONEM) is proposed, an imaging technique that combines non-invasive probing with light, with a high spatial resolution read-out via electron optics. Close to the specimen, the optical near-fields are converted into a spatially varying electron flux using a planar photocathode. The electron flux is imaged using low energy electron microscopy, enabling label-free nanometric resolution without the need to scan a probe across the sample. The specimen is never exposed to damaging electrons.

physics.app-ph↗

arXiv2020

Fundamental bounds on the precision of classical phase microscopes

A wide variety of imaging systems have been designed to measure phase variations, with applications from physics to biology and medicine. In this work, we theoretically compare the precision of phase estimations achievable with classical phase microscopy techniques, operated at the shot-noise limit. We show how the Cram\'{e}r-Rao bound is calculated for any linear optical system, including phase-contrast microscopy, phase-shifting holography, spatial light interference microscopy, and local optimization of wavefronts for phase imaging. Through these examples, we demonstrate how this general framework can be applied for the design and optimization of classical phase microscopes. Our results show that wavefront shaping is required to design phase microscopes with optimal phase precision.

physics.optics↗

arXiv2019

Design for a 10 KeV Multi-Pass Transmission Electron Microscope

Multi-pass transmission electron microscopy (MPTEM) has been proposed as a way to reduce damage to radiation-sensitive materials. For the field of cryo-electron microscopy (cryo-EM), this would significantly reduce the number of projections needed to create a 3D model and would allow the imaging of lower-contrast, more heterogeneous samples. We have designed a 10 keV proof-of-concept MPTEM. The column features fast-switching gated electron mirrors which cause each electron to interrogate the sample multiple times. A linear approximation for the multi-pass contrast transfer function (CTF) is developed to explain how the resolution depends on the number of passes through the sample.

physics.app-ph↗

arXiv2019

Programmable linear quantum networks with a multimode fibre

Reconfigurable quantum circuits are fundamental building blocks for the implementation of scalable quantum technologies. Their implementation has been pursued in linear optics through the engineering of sophisticated interferometers. While such optical networks have been successful in demonstrating the control of small-scale quantum circuits, scaling up to larger dimensions poses significant challenges. Here, we demonstrate a potentially scalable route towards reconfigurable optical networks based on the use of a multimode fibre and advanced wavefront-shaping techniques. We program networks involving spatial and polarisation modes of the fibre and experimentally validate the accuracy and robustness of our approach using two-photon quantum states. In particular, we illustrate the reconfigurability of our platform by emulating a tunable coherent absorption experiment. By demonstrating reliable reprogrammable linear transformations, with the prospect to scale, our results highlight the potential of complex media driven by wavefront shaping for quantum information processing.

quant-ph↗

arXiv2018

Efficient wide-field FLIM

Nanosecond temporal resolution enables new methods for wide-field imaging like time-of-flight, gated detection, and fluorescence lifetime. The optical efficiency of existing approaches, however, presents challenges for low-light applications common to fluorescence microscopy and single-molecule imaging. We demonstrate the use of Pockels cells for wide-field image gating with nanosecond temporal resolution and high photon collection efficiency. Two temporal frames are obtained by combining a Pockels cell with a pair of polarizing beam-splitters. We show multi-label fluorescence lifetime imaging microscopy (FLIM), single-molecule lifetime spectroscopy, and fast single-frame FLIM at the camera frame rate with $10^3 - 10^5$ times higher throughput than single photon counting. Finally, we demonstrate a space-to-time image multiplexer using a re-imaging optical cavity with a tilted mirror to extend the Pockels cell technique to multiple temporal frames. These methods enable nanosecond imaging with standard optical systems and sensors, opening a new temporal dimension for low-light microscopy.

physics.optics↗

arXiv2018

Local Optimization of Wave-fronts for high sensitivity PHase Imaging (LowPhi)

Phase microscopy is an invaluable tool in the biosciences and in clinical diagnostics. The sensitivity of current phase microscopy techniques is optimized for one specific mean phase value and varies significantly across a given sample. Here, we demonstrate a technique based on wavefront shaping that optimizes the sensitivity across the field of view and for arbitrary phase objects. A significant mean sensitivity enhancement is achieved, both for engineered test samples, as well as for red blood cells. Besides sensitivity enhancement, the technique homogenizes sensitivity, reduces typical phase imaging artifacts such as halos, and allows for quantitative single-frame microscopy, which potentially allows for imaging speedup as compared to other phase stepping techniques.

physics.optics↗