Quantum Photonics on a Chip

Before quantum information technologies can become part of everyday life, quantum devices will need to become cheaper and more compact. The integration of quantum optical components into a solid-state chip would be a major step in that direction. Silicon-based chips, which can be integrated with existing CMOS electronics, would be a natural choice, but other materials may offer better performance. In particular, a larger optical nonlinearity would be needed to realize efficient sources of entangled photons—key components of any quantum system. As reported in Physical Review Letters, Ping Xu at Nanjing University, China, and co-workers have demonstrated a powerful alternative based on lithium niobate (LN)—a material sometimes heralded as the “silicon of photonics.”