# Multi-Dimensional Spectroscopy with Intense Entangled Beams: Entanglement-Enabled Phase Matching in a Collinear Beam Geometry

## TL;DR

This paper introduces a new method for quantum molecular spectroscopy using intense entangled beams to improve signal quality and simplify setup.

## Contribution

A novel approach for using intense entangled beams in multi-dimensional spectroscopy that retains quantum advantages and simplifies phase matching.

## Key findings

- Intense entangled beams can be used to generate purely quantum spectroscopic signals.
- The method enables phase-matched signals in a collinear beam geometry.
- The approach is applicable to odd-ordered nonlinear spectroscopies.

## Abstract

The experimental realization of quantum molecular spectroscopy
with entangled photons remains challenging owing to the low signal-to-noise
ratio resulting from the use of low-flux entangled photons. High-flux
entangled photons via intense entangled beams can be used to improve
the signal-to-noise ratio, but the presence of unentangled photons
contaminates the quantum signal stemming from entangled photons. Here,
we demonstrate how intense entangled beams can be used in multi-dimensional
spectroscopy while retaining the advantage of photon entanglement.
Our approach is broadly applicable to odd-ordered nonlinear spectroscopies,
and it generates purely quantum spectroscopic signals. The proposed
approach allows the recording of desired phase-matched signals even
in a collinear beam geometry, which lifts the requirement of complicated
beam geometry setups for phase matching in multi-dimensional spectroscopies.