Light writes info into atoms

Researchers from the Danish Quantum Optics Center, the Max Planck Institute for Quantum Optics, and the Free University of Brussels in Belgium have demonstrated that it is possible to transfer information encoded in the properties of photons to atoms.

The researchers showed that the transfered information could be stored as long as four thousands of a second, which is long enough to carry out computations on it. The method is efficient and has a fidelity, or ability to avoid errors, that is higher than previous research efforts to transfer information from photons to atoms, according to the researchers.

The method could be used to provide a buffer for information carried by light signals. It could also be used as memory for quantum computers, which use the attributes of particles like photons and atoms to compute. Quantum computers have the potential to be many orders of magnitude faster than conventional computers for certain types of very large problems, including solving the difficult mathematics underlying most of today's encryption codes.

The researchers demonstrated the method by transferring information stored in a weak laser pulse to spin-polarized, or magnetically aligned, cesium atoms.

They fired the laser pulse through a cloud of atoms, measured the information-storing properties of the photons, then set a radio-frequency magnetic pulse that, combined with the effect of the laser beam, transfered the information to the atoms. Reversing the process allowed them to read the information stored in the atoms.

The researchers' next steps include increasing the speed of information transfer, implementing the memory in a solid rather than a gas, and demonstrating that the memory can work for the entangled and single-photon states used by quantum computers.

The quantum memory could be used in practical applications and 5 to 15 years, according to the researchers. The work appeared in the November 25, 2004 issue of Nature.