Coupling free electrons to a trapped-ion quantum computer
Elias Pescoller, Santiago Beltrán-Romero, Sebastian Egginger, Nicolas Jungwirth, Martino Zanetti, Dominik Hornof, Michael S. Seifner, Iva Březinová, Philipp Haslinger, Thomas Juffmann, Johannes Kofler, Philipp Schindler, Dennis Rätzel
quant-phSubmitted Jan 16, 2026• Announced Jan 19, 2026• 0 citations
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.
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.
In electron microscopy, the pursuit of atomic-scale resolution for imaging biological [1] samples and soft-matter systems [2] is perpetually constrained by beam-induced sample degredation. While classical approaches attempt to optimize the trade-off between dose efficiency and image quality, they remain fundamentally limited by the physical interactions between electrons and the sample. Quantum technologies, however, present a transformative opportunity by enhancing information extraction per electron without increasing exposure [3], thereby breaking through classical constraints. In this work, we integrate for the first time a trapped-ion qubit into a transmission electron microscope, leveraging the strong Coulomb interaction between swift electrons and Ca⁺ ions [4], along with the precise control and readout capabilities of trapped Ca⁺ ions [5]. By harnessing quantum coherence and controlled interactions, this hybrid approach seeks to advance the capabilities of low-dose imaging, improving the analysis of radiation-sensitive samples while minimizing damage. For this purpose, we customize a transmission electron microscope to provide the required ultra-high-vacuum integrity and adapt the Ca⁺ trap design, including laser cooling and state readout/manipulation, to the geometric constraints of the microscope’s pole-piece gap.
Quantum Computing enhanced Electron Microscopy (QCEM) aims to supplement the classical detector in electron microscopy (EM) with a quantum computer consisting of a trapped-ion lattice. This approach opens the door to a world of novel sensing and imaging techniques. The key ingredient to their development is a thorough understanding of the coupling of free electrons to the vibrational modes of a trapped-ion quantum computer. Here we present initial results, evaluating the scattering matrix elements in different coupling strength regimes, demonstrating the applicability of approximations, and exploring possible use cases of the coupling of a free-electron beam to a quantum computer.
Quantum electron microscopy is an emerging research field at the intersection of electron microscopy, quantum optics, and nanophotonics. Free electrons can serve as powerful quantum probes, on par with photons in their ability to carry and transfer quantum information, generate entanglement within and with a specimen, and reveal previously inaccessible details on nanoscale quantum phenomena [1]. However, quantum experiments are generally highly sensitive to decoherence arising from interactions with residual gas particles, making ultra-high vacuum (UHV) conditions sometimes essential. UHV environments are also required in transmission electron microscopes (TEMs) for the investigation of contamination-sensitive materials [2, 3]. In our project, we aim to combine a trapped-ion quantum computer with a TEM to realise Quantum-Computer-Enhanced Electron Microscopy (QCEM) (www.qcem.info). In this scheme, coherent interactions between free electrons and a trapped ion require vacuum conditions beyond the standard TEM operation [4]. Although UHV-TEM systems have previously been realised [2,3, 5-7], achieving base pressures in the 10⁻⁹ mbar range or better typically involves significant financial investment, long implementation times, and close collaboration with manufacturers. We present a cost-effective, minimally invasive modification to the vacuum system of a JEOL JEM-2100F to reduce the base pressure at the sample position to below 5 × 10⁻⁹ mbar. Our approach is to integrate two additional 50 L/s NEG-ion pumps mounted on flanges near the sample region, with no structural modifications to the microscope. The NEG pumps are integrated into the microscope workflow through controlled activation and regeneration cycles compatible with standard TEM operation. This work represents a practical step toward enabling the realisation of QCEM, and the concept enables a relatively rapid implementation at a moderate cost, which can, in principle, be adapted to any TEM that provides suitable flange access to the sample chamber.
Free-electron quantum optics provides a versatile platform for manipulating electrons at the quantum level with potential applications in quantum information technologies. We propose a grating-based architecture for fully quantized free-electron quantum optics, in which photon-electron interactions map onto Jaynes-Cummings and Tavis-Cummings models via Bloch-Floquet analysis. Within this framework, we design ultrafast single- and two-qubit gates with cavity-free flying electrons, enabling universal quantum computing in experimentally accessible setups. More broadly, this framework establishes a platform for probing free-electron quantum optics and advancing quantum technologies in simulation, sensing, and information processing.
Free electrons provide a powerful tool for probing material properties at atomic resolution. Recent advances in ultrafast electron microscopy enable the manipulation of free-electron wave functions using laser pulses. It would be of great importance if one could combine the spatial resolution of electron microscopes with the ability of laser pulses to probe coherent phenomena in quantum systems. To this end, we propose a novel concept that leverages free electrons that are coherently shaped by laser pulses to measure quantum coherence in materials. We develop the quantum theory of interactions between shaped electrons and arbitrary qubit states in materials, and show how the postinteraction electron energy spectrum enables measuring the qubit state (on the Bloch sphere) and the decoherence or relaxation times (T_{2}/T_{1}). Finally, we describe how such electrons can detect and quantify superradiance from multiple qubits. Our scheme can be implemented in ultrafast transmission electron microscopes (UTEM), opening the way toward the full characterization of the state of quantum systems at atomic resolution.
Examining and controlling the interaction between semiconductor quantum qubits and their environment can boost semiconductor quantum technologies, which have many applications in table-top quantum computing hardware. Electron beams in electron microscopes have opened up a new avenue for the quantum-coherent probing of semiconductor excitations and strong-coupling effects. Here, I provide a brief overview of recent advancements in electron-beam probes for investigating quantum coherence in semiconductors and two-dimensional materials, complemented by my perspective on using electron beams to manipulate the entanglement and correlations between quantum systems.