Full paper here: Heralded generation of entanglement with photons
Entanglement is one of the strangest features of quantum physics: two or more particles become linked so that what happens to one instantly affects the others, no matter how far apart they are. These “spooky actions,” as Einstein famously called them, no longer remain just a pursuit of human curiosity—they are now the foundation of many emerging quantum technologies.
Among the most promising carriers of entanglement are photons, the particles that light is made up of. Yet because photons barely interact with one another, making an entangled configuration with them is very challenging. The most common method today, called postselection, is wasteful: the desired photonic configuration is destroyed in the very act of verifying its presence.
A more powerful approach, known as heralded generation, avoids this trap. Here, extra “helper” photons act as signals, measuring them confirms that the entanglement generation process has succeeded while leaving the useful photons untouched. This not only preserves the entangled states but also allows success rates to be boosted by running many attempts in parallel, paving the way toward scalable quantum systems.
Working together with colleagues at the University of Bristol, we have reviewed the full range of strategies for generating entangled photons. We explore how the alternative approach of heralding can be exploited to overcome the limitations of postselection and drive forward the field of photonic quantum technologies and shed light on how heralded generation of entanglement could power quantum computers built on light, enable ultra-secure communication networks, sharpen measurements for science and technology, and even test the limits of fundamental physics.