Realization of quantum memory for light allows the extension of quantum communication far beyond 100 km
In the macroscopic classical world, it is possible to copy information from one device into another. We do this everyday, when, for example, we copy files in a computer or we tape a conversation. In the microscopic world, however, it is not possible to copy the quantum information from one system into another one. It can only be transferred, without leaving any trace on the original one. The manipulation and transfer of quantum information is, in fact, a very active field of research in physics and informatics, since it is the basis of all the protocols and algorithms in the fields of quantum communication and computation, which may revolutionize the world of information. In the work published in Nature, November 25, 2004, scientists from the Max Planck Institute for Quantum Optics in Garching and the Niels Bohr Institute in Copenhagen have proposed a scheme to transfer the quantum state of a pulse of light onto a set of atoms and have demonstrated it experimentally.