Heralded generation of entangled photon pairs

TL;DR

This paper demonstrates the first heralded generation of maximally polarization-entangled photon pairs using linear optics and standard detection, advancing quantum communication and computation capabilities.

Contribution

It introduces a method for heralded entangled photon pair generation from spontaneous parametric down-conversion with auxiliary photon detection, improving reliability over probabilistic sources.

Findings

Successful heralded generation of entangled photon pairs

Use of four auxiliary photon detections for unambiguous heralding

Enhancement of quantum network applications like teleportation and cryptography

Abstract

Entangled photons are a crucial resource for quantum communication and linear optical quantum computation. Unfortunately, the applicability of many photon-based schemes is limited due to the stochastic character of the photon sources. Therefore, a worldwide effort has focused in overcoming the limitation of probabilistic emission by generating two-photon entangled states conditioned on the detection of auxiliary photons. Here we present the first heralded generation of photon states that are maximally entangled in polarization with linear optics and standard photon detection from spontaneous parametric down-conversion. We utilize the down-conversion state corresponding to the generation of three photon pairs, where the coincident detection of four auxiliary photons unambiguously heralds the successful preparation of the entangled state. This controlled generation of entangled photon states is a significant step towards the applicability of a linear optics quantum network, in particular for entanglement swapping, quantum teleportation, quantum cryptography and scalable approaches towards photonics-based quantum computing.