Quantum States of Light

Ulf Leonhardt

Adi Ben Hayun, Ori Reinhardt, Jonathan Nemirovsky +3 more

It is a long-standing goal to create light with unique quantum properties such as squeezing and entanglement. We propose the generation of quantum light using free-electron interactions, going beyond their already ubiquitous use in generating classical light. This concept is motivated by developments in electron microscopy, which recently demonstrated quantum free-electron interactions with light in photonic cavities. Such electron microscopes provide platforms for shaping quantum states of light through a judicious choice of the input light and electron states. Specifically, we show how electron energy combs implement photon displacement operations, creating displaced-Fock and displaced-squeezed states. We develop the theory for consecutive electron-cavity interactions with a common cavity and show how to generate any target Fock state. Looking forward, exploiting the degrees of freedom of electrons, light, and their interaction may achieve complete control over the quantum state of the generated light, leading to novel light statistics and correlations.

Marc-Oliver Pleinert

Marcus Blackwell

This short paper builds on the Three States of Light theory (DOI: 10.5281/zenodo.20132207). It explores the implications for quantum computing, showing that heat generation is a property of Crystallized Light (matter-based qubits), not Bound Light (photonic quibits). Photonic quantum computing is therefore intrinsically lossless. A speculative third regime (Unbound Light) would generate zero heat. The paper does not claim to invent photonic quantum computing. It cites prior work (KLM 2001, O'Brien 2007, Rudolf 2017, etc.) and uses the Three States of Light framework to explain why photonic qubits have inherent advantages over matter-based qubits. Keywords: quantum computing, photonic quantum computing, three states of light, Bound Light, Crystallized Light, heat dissipation, Unbound Light Version 1 - May 12, 2026

Muhammad Hamza Waseem, Faizan-e-Ilahi, Muhammad Sabieh Anwar

Xiaolong Dong, Dongyu Liu, Mingsheng Tian +6 more

Ghost imaging can be implemented with illumination light with pronounced quantum characters. In this work, we address the inverse problem of ghost imaging, i.e., the tomography of the quantum states of illumination light based on ghost imaging. We showcase the characterization of multimode Gaussian state light represented by its covariance matrix. With the information of spatial modes, we reconstruct the quantum states of light using the variation of SNR of the ghost images formed by the input light under a given set of optical operations. We demonstrate that ghost imaging can also be used to characterize the non-Gaussian light by its deviation from Gaussian states, which can serve as a criterion for the non-Gaussianity of the input light. The spatial resolving power of the proposed method can be advantageous for quantum information applications involving structured light, such as multiplexing with spatial modes.