Observing the transition from quantum to classical energy correlations with photon pairs

TL;DR

This paper presents an experimental method to control and observe the transition from quantum to classical energy correlations in photon pairs by applying random spectral phases, revealing how decoherence affects their energy entanglement.

Contribution

It introduces a novel technique to tune the quantum-classical correlation balance in photon pairs and demonstrates the transition through spectral phase manipulation.

Findings

Diverging temporal second order correlation function observed.

Transition from energy entangled to classically correlated states demonstrated.

Spectral phase randomization induces decoherence in energy basis.

Abstract

We experimentally demonstrate a method to control the relative amount of quantum and classical energy correlations between two photons from a pair emitted by spontaneous parametric downconversion. Decoherence in the energy basis is achieved by applying random spectral phases on the photons. As a consequence a diverging temporal second order correlation function is observed and is explained by a mixture between an energy entangled pure state and a fully classically correlated mixte state.