Quantum network blazes data storage and retrieval speed record

Researchers looking to improve the prospects for long-distance quantum networks set a speed record for the time quantum data needed to be storied and retrieved.

The new record - 7 milliseconds for rubidium atoms stored in a system known as a dipole optical trap - smashed the old record of 32 microseconds, a difference of more than two orders of magnitude, researchers said.

The general purpose of quantum networking or quantum computing is to distribute entangled qubits - two correlated quantum data bits that are either "0" or "1" - over long distances, researchers said. The qubits would travel as photons across existing optical networks but because of loss in the optical fiber that makes up networks, repeaters must be installed at regular intervals - about every 100 kilometers - to boost the signal, researchers stated. Those repeaters will need quantum memory to receive the photonic signal, store it briefly and then produce a photonic signal that will carry the information to the next node, and on to its final destination, researchers said.

For the record setting research Georgia Tech researchers used a group of rubidium-87 atoms cooled to almost absolute zero to minimize atomic motion. To store information, the entire group is exposed to laser light carrying a signal, which lets each atom participate in the storage as part of a "collective excitation." Researchers said each atom "sees" the incoming signal - which is a rapidly oscillating electromagnetic field - slightly differently. Each atom is therefore imprinted with information that can later be "read" from the ensemble with another laser.

Because each atom stores a portion of the quantum information and that data's usefulness depends on each atom's location in reference to other atoms, significant movement of the atoms could destroy the information, researchers said. The keys to extending the storage time included the use of a one-dimensional optical lattice to help confine the atoms and selection of an atomic phase that is insensitive to magnetic effects..

"For multiple architectures with many memory elements, several milliseconds would allow the movement of light across a thousand kilometers," said Alex Kuzmich, associate professor in the Georgia Tech School of Physics and a co-author of the paper on the research. Though the work significantly advances quantum memories, practical quantum networks probably are at least a decade away, Kuzmich said.

The study is sponsored by the National Science Foundation, the A.P. Sloan Foundation and the U.S. Office of Naval Research.

Quantum networking has held the interest of a broad swath of groups for a few years now.  Recently, for example,  the US Army Research Office and the National Security Agency (NSA) said they were looking for some answers to their quantum physics questions.  Specifically the groups are looking to:

-develop new quantum computing algorithms for hard computational problems;

-characterize the efficiency of candidate quantum algorithms;

-develop insights into the power of quantum computation and consider issues of quantum complexity and computability.

In March, the Defense Advanced Research Projects Agency said it was looking for  innovative research proposals in the intriguing area of quantum entanglement --  a developing component of quantum physics that looks at the behavior between atoms and  photons that could ultimately play a key role in developing security, unbelievably fast networks and even teleportation.

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