# Entangled Excitons via Spontaneous Downconversion

## TL;DR

This paper demonstrates how certain molecular arrangements can produce entangled exciton pairs with potential applications in quantum technologies, using a combination of theory and simulation.

## Contribution

It introduces a novel method to generate entangled excitons via spontaneous downconversion in molecular systems, analogous to optical parametric downconversion.

## Key findings

- Entangled excitons can be generated in molecular chains.
- Bell states of excitons are achievable through engineered molecular arrangements.
- Theoretical and numerical analysis supports the feasibility of excitonic entanglement.

## Abstract

A class of centrosymmetric molecules support excitons with a well-defined quasi-angular momentum. Cofacial arrangements of these molecules can be engineered so that quantum cutting produces a pair of excitons with angular momenta that are maximally entangled. The Bell state constituents can subsequently travel in opposite directions down molecular chains as ballistic wave packets. This is a direct excitonic analog to the entangled polarization states produced by the spontaneous parametric downconversion of light. As in optical settings, the ability to produce Bell states should enable foundational experiments and technologies based on non-local excitonic quantum correlation. The idea is elucidated with a combination of quantum electrodynamics theory and numerical simulation.