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Upper bound for the quantum coupling between free electrons and photons

Zhao Z (2025)

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Publication Type: Conference contribution

Publication year: 2025

Publisher: Institute of Electrical and Electronics Engineers Inc.

Conference Proceedings Title: 2025 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2025

Event location: Munich, DEU

ISBN: 9798331512521

DOI: 10.1109/CLEO/EUROPE-EQEC65582.2025.11109778

Abstract

The fundamental limit of free-electron-light coupling is an important question relevant to frontier studies to reach the strong coupling regime, which is crucial for applications such as free-electron based photon sources, quantum sensing and quantum computing using free electrons [1,2]. This study rigorously establishes the fundamental upper bound of free-electron-photon coupling [3]. The upper bound depends on the optical medium, the electron velocity, the separation distance, and the interaction length, which is applicable to arbitrary structures enclosed within a design region (Fig. 1(a)). When the photonic modes have a discrete spectrum as in the case of a lossless optical cavity, the upper bound for the free-electron-photon coupling coefficient (gQu,m) is q²e |gQu,m|² < g²ub ≡ (Equation presented), where g²geo = (Equation presented), ε is the relative perε mittivity, χ = ε − 1, L is the interaction length, k = ω/c = 2π/λ, ω is the optical frequency, λ is the wavelength, ke = ω/v, v is the free-electron velocity, αe = ^√ke² − k², ρ is the transverse distance towards the electron trajectory, K0, K1 are the modified Bessel functions of the second kind with order 0 and 1 respectively, and the design region R is expanded by a transverse cross section R⊥ and a longitudinal length L.

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How to cite

APA:

Zhao, Z. (2025). Upper bound for the quantum coupling between free electrons and photons. In 2025 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2025. Munich, DEU: Institute of Electrical and Electronics Engineers Inc..

MLA:

Zhao, Zhexin. "Upper bound for the quantum coupling between free electrons and photons." Proceedings of the 2025 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2025, Munich, DEU Institute of Electrical and Electronics Engineers Inc., 2025.

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