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Programming Coherent and Quantum Light with a Free-Electron Wavepacket

Songyu Zhu1,2, Yushan Zeng1,3,*, Chenhao Pan1,2, Yiming Pan2,†, Ye Tian1,3,‡, and Ruxin Li1,2,3,4,§

  • *Contact author: yszeng@siom.ac.cn
  • †Contact author: yiming.pan@shanghaitech.edu.cn
  • ‡Contact author: tianye@siom.ac.cn
  • §Contact author: ruxinli@siom.ac.cn
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Phys. Rev. Lett. 137, 143601 – Published 29 September, 2026

DOI: https://doi.org/10.1103/k2cg-484h

Abstract

The pursuit of programmable light sources with high coherence and spectral purity hinges on establishing a precise set of phase relationships in light-matter interactions. Here, we demonstrate that the quadratic dispersion of a freely propagating electron wave packet serves as a programmable quantum medium. Prepared in a coherent momentum-state ladder via a single laser interaction, the electron subsequently undergoes deterministic phase evolution during free propagation—an intrinsic process that compiles its quantum state into two distinct output channels. This mechanism, quantified by a quantum bunching factor, enables (i) Talbot-resonant bunching, where the electron density self-structures into subcycle combs with tunable harmonic selectivity, and (ii) coherent phase transfer of the programmed quadratic phase to light, generating nonclassical photon states such as multicomponent Schrödinger cat states via energy-resolved electron readout. This quadratic-phase programming provides a drift-section platform for Talbot-selected coherent short-wavelength emission and nonclassical light synthesis based on electron self-interference.

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Phys. Rev. Lett. 137, 143601– Published 29 September, 2026
  • Received 30 March 2026
  • Accepted 11 August 2026
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