Emerging Connections: Classical and Quantum Optics

Quantum optics and classical optics have coexisted for nearly a century as two distinct, self-consistent descriptions of light. What influences there were between the two domains all tended to go in one direction, as concepts from classical optics were incorporated into quantum theory’s early development. But it’s becoming increasingly clear that a significant quantum presence exists in classical territory—and, in particular, that the quintessential quantum attribute, entanglement, can be seen, studied and exploited in classical optics.