High-efficiency quantum interrogation measurements via the quantum Zeno effect

The phenomenon of quantum interrogation allows one to optically detect the presence of an absorbing object, without the measuring light interacting with it. In an application of the quantum Zeno effect, the object inhibits the otherwise coherent evolution of the light, such that the probability that an interrogating photon is absorbed can in principle be arbitrarily small. We have implemented this technique, demonstrating efficiencies exceeding the 50% theoretical-maximum of the original ``interaction-free'' measurement proposal. We have also predicted and experimentally verified a previously unsuspected dependence on loss; efficiencies of up to 73% were observed and the feasibility of efficiencies up to 85% was demonstrated.Comment: 4 pages, 3 postscript figures. To appear in Phys. Rev. Lett; submitted June 11, 199

Growth mechanism of iron-filled carbon nanotubules

Iron-filled nanotubules were synthesized in a carbon are in the presence of He and Fe(CO)(5) gases. The consumption of the Fe(CO)(5) inside the are chamber was controlled by the pressure of the pentacarbonyliron Fe(CO)(5) gas. Different shapes and filling extents of nanotubules were found depending on the pentacarbonyliron concentration supplied. Based on high-resolution transmission electron microscope images, we propose a growth model of iron-filled carbon nanotubules. The growth proceeds through the deposition and surface diffusion of carbon on the liquidlike metal. The hollow tubules probably grow spontaneously. (C) 1996 American Institute of Physics