Speaker
Description
Free-electron quantum optics [1] explores quantum-coherent interactions between free-electron wavepackets, light, and matter, enabling ultrafast and deep-subwavelength studies of quantum correlations. A central achievement of the field has been the realization of electron–photon entanglement [2–5]. Beyond this, theory has predicted entanglement between free electrons and bound electrons [6,7], as well as between pairs of free electrons through long-range Coulomb interactions [8]. While classical correlations between free-electron pairs were recently observed experimentally [9,10], direct evidence of residual entanglement remains elusive [8]. Likewise, free-electron–bound-electron entanglement has yet to be experimentally demonstrated [11,12].
In this talk, I will show that entangled free-electron pairs leave distinct signatures in the emitted light that directly depend on their quantum state [13], providing a route for optical detection of free-electron entanglement. I will then discuss recent experiments showing that Coulomb-entangled electron pairs driven by external laser fields exhibit characteristic two-dimensional quantum-walk–like energy-correlation patterns [8], clearly different from separable states. Next, I will present a new mechanism in which elastic interactions with electromagnetic fields generate entangled electron energy-comb states [14]. Finally, I will discuss how engineered electromagnetic environments can strongly enhance free-electron–bound-electron interactions [15,16], bringing experimental observation of this form of entanglement closer to reality.
References
[1] R. Ruimy, et al., Nat. Phys. 21, 193 (2025).
[2] O. Kfir, Phys. Rev. Lett. 123, 103602 (2019).
[3] G. Arend, et al., Nat. Phys. 21, 1855 (2025).
[4] Henke et al, arXiv :2504.13047 (2025)
[5] Rembold et al, arXiv :2502.19536 (2025)
[6] R. Ruimy, et al., Phys. Rev. Lett. 126, 233403 (2021).
[7] Z. Zhao, et al., Phys. Rev. Lett. 126, 233402 (2021).
[8] O. Tziperman, et al., Nat. Phys. 22 763 (2025).
[9] R. Haindl, et al., Nat. Phys. 19, 1410 (2023).
[10] S. Meier, et al., Nat. Phys. 19, 1402 (2023).
[11] Kolb et al, arXiv:2509.13904 (2025).
[12] Grzesik et al, arXiv:2508.13112 (2025).
[13] Karnieli et al, Phys. Rev. Lett. 127, 060403 (2021).
[14] Ruimy et al, in preparation (2026)
[15] Karnieli et al, Sci. Adv. 9, add2349 (2023).
[16] Grzesik et al, arXiv 2601:21385 (2026)