Researchers at the Max Planck Institute of Quantum Optics (MPQ) in Garching, Germany have achieved unprecedented control over the creation of single photons (Nature, October 28, 2004). By using a tightly trapped single calcium ion, localized between two ultra-high reflectivity mirrors, and subjecting it to an external laser pulse, the scientists could emit photons one by one. The emission time and the pulse shape of each photon were completely user-controlled. Remarkably, the device was operated without interruption over a period limited only by the trapping time of the ion, typically many hours. The achievement has important applications in quantum information...