Free Electrons Can Induce Entanglement Between Photons

TL;DR

This paper demonstrates that free electrons can induce entanglement and control the quantum coherence of photons, offering a novel nonlocal optical nonlinearity for quantum information applications.

Contribution

It introduces a new mechanism where free electrons create and tune entanglement between photons in separated cavities, expanding quantum control methods.

Findings

Electrons can induce entanglement between spatially separated photons.

Pre-shaping electron wavefunctions tunes photonic quantum correlations.

Electrons provide a nonlocal optical nonlinearity for quantum control.

Abstract

Entanglement of photons is a fundamental feature of quantum mechanics, which stands at the core of quantum technologies such as photonic quantum computing, communication, and sensing. An ongoing challenge in all these is finding an efficient and controllable mechanism to entangle photons. Recent experimental developments in electron microscopy enable to control the quantum interaction between free electrons and light. Here, we show that free electrons can create entanglement and bunching of light. Free electrons can control the second-order coherence of initially independent photonic states, even in spatially separated cavities that cannot directly interact. Free electrons thus provide a type of optical nonlinearity that acts in a nonlocal manner, offering a new way of heralding the creation of entanglement. Intriguingly, pre-shaping the electron's wavefunction provides the knob for tuning the photonic quantum correlations. The concept can be generalized to entangle not only photons but also photonic quasiparticles such as plasmon-polaritons and phonons.