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arXiv:2605.10492

Perspective on tailoring quantum coherence with electron beams

Nahid Talebi

quant-phcond-mat.mes-hallphysics.opticsSubmitted May 11, 2026• Announced May 12, 2026
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Abstract

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.

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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.
The recently emerged field of quantum technology is aiming to employ quantum coherence and entanglement for realization of next generation sensors, standards, imaging systems, secure communication and computers.Although applications of quantum technologies cover a broad spectrum and their development stage varies from early demonstrations to commercially available devices, many challenges have been identified.The first includes tailoring materials for quantum technologies, which is playing an essential role in technological applications of quantum science.Solid state systems allowing long coherence time are essential for quantum computation and quantum sensing.Ultrapure materials with tailored isotopic content are important for reaching long coherence time of spin qubits (Awschalom et al., 2013).The ability to place single dopants with high precision and form spin qubits at desired location is essential for both quantum computing and quantum sensing applications (McCallum et al., 2012;Smith et al., 2019).The performance of different types of qubits is usually benchmarked in terms of controllability and coherence time.Usually solid-state systems allow fast control, but exhibit fast decoherence owing to complex environment.It is therefore important to search for new types of qubits combining isolation from environment and access via fast coherent control and readout.Novel approaches combining different quantum systems into build hybrid quantum devices for optimal performance is a promising avenue.Examples of such hybrid approaches are spin systems coupled to superconducting qubits (Kubo et al., 2011) and hybrid nuclear-electronic qubits (Morley et al., 2013).Optimal protocols for quantum technologies requires extension of coherence time of qubits beyond the coherence time of the isolated quantum system.The efficient protection toolkit includes dynamical decoupling (Yang et al., 2011) and quantum error correction (Terhal, 2015) based techniques.Although general principles of qubits protection were developed and tested experimentally in different model environments, it is essential to adapt them to realistic environmental noise.In the field of quantum sensing, it is also essential to combine protections against noise with non-reduced sensing performance.Experimental imperfections can be addressed using optimal control tools (Glaser et al., 2015).The development of efficient quantum algorithms is another growing field belonging to quantum software area.On one hand, it is essential to find problems where a quantum computer can outperform classical computers.On the other hand, it is essential to develop an application scenario for a limited number of qubits (Montanaro, 2016).In addition, in order to develop new algorithms, future work must include discoveries of application scenarios of already known algorithms.Application of quantum Fourier transform for sensing is a promising example of such new applications (Vorobyov et al., 2021).Signal processing is another field of quantum software that is becoming essential in applications.Advanced signal analysis protocols, like quantum compressed sensing, can be employed to quantify entanglement in large quantum devices via efficient quantum tomography (Riofrío et al., 2017).
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.
Electron--photon quantum entanglement in an electron microscope paves the way for a new quantum platform, enabling the integration of quantum functionalities into electron microscopy and opening opportunities for quantum imaging and quantum sensing at the nanoscale. To realize such a platform, it is crucial to understand the degree and nature of electron--photon entanglement in cathodoluminescence (CL). However, its dependence on electron-beam properties, particularly transverse coherence, remains unclear. Here, we present a theoretical framework describing the quantum state of an electron--photon pair generated in coherent CL from a system with translational invariance in the plane perpendicular to the electron beam, as can be realized, for example, in transition radiation at a planar interface. By expressing the scattered state directly in terms of the luminescence spectrum, we evaluate the entanglement using both subsystem purity and an Einstein--Podolsky--Rosen-type criterion. These two measures enable a clear distinction among wave-like, particle-like, and classical regimes in terms of spatial and momentum entanglement in the electron--photon system. Our analysis identifies the roles of the electron's transverse and longitudinal coherence, as well as the photon's spectral width, and reveals the conditions under which strong spatial entanglement emerges. This unified perspective clarifies the nature of electron--photon quantum correlations in coherent CL and advances the development of quantum-enabled functionalities in electron microscopy.
Two-dimensional (2D) electron/hole gases confined in semiconductor heterostructures suffer from weak Rashba spin-orbit coupling (SOC) for manipulating spin degreee of freedom via an electric rather than a magnetic field. Here, we show that complementary metal-oxide-semiconductor technology-accessible strain could substantially enhance the linear Rashba SOC of the top hole subband in Ge/SiGe quantum wells (QWs) to a level comparable to that of 2D Rashba materials through enhancing the mixture of the light-hole and heavy-hole bands. We further show that strongly enhanced Rashba SOC boosts the Rabi frequency of hole spin qubits confined in Ge/SiGe QWs by two orders of magnitude to an unprecedented 40 GHz, more than one order of magnitude faster than other qubit platforms. We also demonstrate that the hole spin rotation with Rabi frequency > 25 GHz enters a new regime being immune to gate control-induced electric noise, opening a new avenue to simultaneously improve the gate speed and gate fidelity. Our findings provide a new routine to substantially enhance the Rashba SOC in 2D semiconductor hole gases to a level that is great for spintronic applications.