Photons from a quantum dot prove entanglement over time

Researchers at the Beijing Academy of Quantum Information Sciences have demonstrated entanglement not just across space, but across time, using a single quantum dot. The team reports violating the Clauser-Horn-Shimony-Holt Bell inequality by creating and manipulating “vacuum–one-photon number superposition states,” where a photon either exists or does not. This approach bypasses the need to generate multiple photons, simplifying the creation of entangled photons from a solid-state source and offering a scalable pathway for future quantum technologies. Bang Wu of the Beijing Academy of Quantum Information Sciences and colleagues detail their findings in a new study. Researchers observed a Bell inequality violation with a parameter S reaching 2. 675(0.050), exceeding the classical limit of 2 by over 13 standard deviations, confirming the non-local nature of the generated quantum state. This result stems…