# Multichromatic Quantum Superpositions in Entangled Two-Photon Absorption Spectroscopy

## TL;DR

This paper explores how multichromatic quantum superpositions of entangled photon pairs can significantly alter the optical absorption properties of molecules, revealing quantum interference effects that could be observed experimentally.

## Contribution

It introduces a novel approach of using energy superpositions in entangled photon pairs to modify molecular absorption, expanding quantum spectroscopy techniques.

## Key findings

- Quantum superpositions can substantially change molecular absorption cross sections.
- Constructive and destructive interferences are demonstrated in the optical properties.
- Quantum interference effects are more pronounced than constructive ones.

## Abstract

Quantum information science is driving progress in a vast number of scientific and technological areas that cover molecular spectroscopy and matter-light interactions in general. In these fields, the ability to generate quantum mechanically-entangled photons is opening avenues to explore the interaction of molecules with quantum light. This work considers an alternative way of correlating photons by including energy superpositions. We study how the multichromatic quantum superposition, or color superposition of photon-pair states, influences the optical properties of organic chromophores. This work uses electronic structure calculations based on time-dependent density functional theory, and a simple modification of the standard entangled two-photon absorption theory. Our calculations show that it is possible to substantially modify the optical absorption cross section of molecules, where constructive and destructive interferences are computed. The quantum interference effects are more pronounced than the constructive ones. These quantum effects, or related ones, could be observed in quantum spectroscopic experiments where qudit photon states are generated.