January 20, 2000

Quantum memory: it's not just for theorists anymore.

ANN ARBOR—Using ultrafast lasers and a beam of cesium atoms, University of Michigan physicists have created a database that stores and retrieves data in atomic quantum phase, instead of the bits and bytes used by today's computers.

The U-M experiment is the first to test a theoretical approach to using quantum phase for data storage and retrieval, which was proposed by L.K. Grover in a 1997 paper published in Physics Review Letters. Results of the study by Philip H. Bucksbaum , the Otto Laporte Professor of Physics at U-M, and U-M graduate students Jaewook Ahn and Thomas C. Weinacht were published in the Jan. 21 issue of Science.

Understanding the U-M study requires diving into the murky field of quantum mechanics—the study of the indivisible bundles of energy that make up light and matter. The laws of quantum mechanics control an atom's structure, motion and behavior. In the quantum world, electrons behave like waves sloshing in your bathtub. Electrons can exist simultaneously in an infinite number of locations or quantum states within the wave.

In the U-M experiment, a computer randomly assigned data to one quantum state in a single cesium atom. Using a pulse of ultrashort, intense laser light, U-M scientists stored the information in the assigned quantum state by flipping the quantum phase or literally inverting the quantum wave for that state. Less than one nanosecond or billionth of a second later, the same atom was hit by a second laser pulse, which located the stored data by amplifying the flipped quantum state and suppressing all other states in the wave packet.

"L.K. Grover speculated that quantum data registers would be a faster, more efficient way to store and retrieve data than the binary system we use today, because the rules of quantum mechanics allow you to search many locations simultaneously. We tested one of his algorithms and confirmed Grover's idea," Bucksbaum said.

"It is important to keep this study in perspective," Bucksbaum added. "Quantum phase data storage is a new concept. Most researchers are using the spin of a quantum particle as a storage medium. Our work may turn out to be a step on the pathway to a viable quantum computer system or it could be a complete dead-end. The field is still too new to know which approach will succeed."

The research study was funded by the National Science Foundation.

Contact: Sally Pobojewski
Phone: (734) 647-8814
E-mail: pobo@umich.edu