Heralded generation of entanglement with photons

TL;DR

This paper reviews heralded photon entanglement generation, highlighting its advantages over postselection, discussing theoretical and experimental progress, and exploring applications in quantum computing, communication, and metrology.

Contribution

It provides a comprehensive overview of heralded entangled photon generation methods, including recent experimental advances and potential applications in quantum technologies.

Findings

Heralded generation improves scalability and usability of entangled photons.

Experimental techniques have advanced, demonstrating practical heralded entanglement.

Applications span quantum computing, communication, and precision measurement.

Abstract

Entangled states of photons form the backbone of many quantum technologies. Due to the lack of effective photon-photon interactions, the generation of these states is typically probabilistic. In the prevailing but fundamentally limited generation technique, known as postselection, the target photons are measured destructively in the generation process. By contrast, in the alternative approach -- heralded state generation -- the successful creation of a desired state is verified by the detection of ancillary photons. Heralded state generation is superior to postselection in several critical ways: It enables free usage of the prepared states, allows for the success probability to be arbitrarily increased via multiplexing, and provides a scalable route to quantum information processing using photons. Here, we review theoretical proposals and experimental realizations of heralded entangled photonic state generation, as well as the impact of realistic experimental errors. We then discuss the wide-ranging applications of these states for quantum technologies, including resource states in linear optical quantum computing, entanglement swapping for repeater networks, fundamental physics, and quantum metrology.