Scientists at the National Institute of Standards and Technology have enticed six atoms into spinning simultaneously in two opposite directions in an experiment that could advance quantum computing.
Researchers believe quantum computers could solve problems exponentially faster than today's computers of a similar size. It would take today's supercomputers years to break the best encryption code employed to protect bank transactions, for instance. Quantum computers could quickly decipher codes. Researchers see quantum computers being used to optimize complex systems such as airline schedules and database searching, develop fraud-proof digital signatures, or simulate complex biological systems to create new drugs.
The experiment, along with another one conducted by Austrian researchers, are described in the Dec. 1 issue of the science journal Nature.
NIST said in a statement Wednesday that its scientists entangled six beryllium ions, or charged atoms, so that their nuclei were collectively spinning clockwise and counterclockwise at the same time. "Entanglement, which Albert Einstein called 'spooky action at a distance,' occurs when the quantum properties of two or more particles are correlated," said NIST, an arm of the U.S. Department of Commerce.
The experiments break new ground for entanglement of multiple particles in the laboratory. The previous record was five entangled photons, the smallest particles of light. "It is very difficult to control six ions precisely for a long enough time to do an experiment like this," physicist Dietrich Leibfried, lead author of the NIST paper, said in the statement.
Existing in two states at once is a property of quantum physics known as superposition. In the NIST experiment, scientists placed ions in the most extreme superposition of spin states possible with six ions. All six nuclei are spinning in one direction and the opposite direction simultaneously or what physicists call Schrdinger cat states. The name, coined in a 1935 essay by German physicist Erwin Schrdinger, describes an extreme theoretical case of being in two states simultaneously, namely a cat that is dead and alive.
Cat states are superpositions of opposite overall properties that are fairly simple to confirm, and might be valuable in a NIST-envisioned design for fault-tolerant quantum computers. Cat states also are more sensitive to disturbance than other types of superpositions, which might be useful in some forms of quantum encryption, furnishing new ways to protect information by making nearly all eavesdropping noticeable, NIST said.
The Advanced Research and Development Activity/National Security Agency, the Department of Defense Multidisciplinary University Research Initiative Program administered by the Office of Naval Research, and NIST funded the research.