Thomas Juffmann

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 nondestructive, 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.

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), demonstrating super-resolved multiplexed imaging of spectrally overlapping fluorophores, enhanced contrast due to optical sectioning, and environmental sensing at a spatial resolution of 156 nm. The high photon detection throughput of EOFLIM enables a combination of lifetime precision, size of the field of view, spatial resolution, and speed, which, taken together, is unprecedented, enabling the super-resolved imaging of cellular dynamics.

Coherent interferometric scattering microscopy (i scat ) 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 for spherical subwavelength scatterers in a homogeneous medium under oblique illumination in i scat 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, 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.

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.

Single-electron detectors are a key component of electron microscopes and advanced electron optics experiments. We present a scintillator-based single-electron detector with an estimated spatial resolution of 0.9 μm 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.

We employ the concept of quantum Fisher information to optimize the focused excitation fields in coherent scattering microscopy. Our optimization goal is to achieve the best possible localization precision for small scatterers located above a glass coverslip, while keeping the intensity of the total incoming excitation fields fixed. For small numerical aperture (NA) values, the optimal fields have linear or circular polarization, and the excitation beam can be well approximated by a Gaussian one. For larger NA values, the optimal beam acquires radial polarization. We show that the high localization precision can be attributed to high field strengths at the scatterer position, and correspondingly a large number of scattered and detected photons. Finally, we evaluate the performance of the optimized beams in interferometric scattering microscopy (i scat ), and further optimize these fields for i scat localization using the concept of Fisher information.

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.

Aberration correction is crucial for achieving atomic resolution in electron microscopy. While conventional correctors use multipolar electron lenses, our work explores a fundamentally different approach tailored specifically for ultrafast electron microscopes operating in pulsed mode. We propose using spatially structured intense laser pulses to manipulate electron wave fronts via free-space electron-photon interactions. Our simulations demonstrate that such laser fields can effectively compensate for the spherical and chromatic aberrations of subsequent magnetic lenses, resulting in substantial improvements in probe size. These findings pave the way for optical elements designed for ultrafast electron microscopy.

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.