Key Concepts

• Quantum computers can store and process data using atoms, photons or fabricated microstructures. These machines may someday be able to perform feats of computing once thought to be impossible.
• The manipulation of trapped ions is at the forefront of the quantum computing effort. Researchers can store data on the ions and transfer information from one ion to another.
• Scientists see no fundamental obstacles to the development of trapped-ion computers.

Over the past several decades technological advances have dramatically boosted the speed and reliability of computers. Modern computer chips pack almost a billion transistors in a mere square inch of silicon, and in the future computer elements will shrink even more, approaching the size of individual molecules. At this level and smaller, computers may begin to look fundamentally different because their workings will be governed by quantum mechanics, the physical laws that explain the behavior of atoms and subatomic particles. The great promise of quantum computers is that they may be able to perform certain crucial tasks considerably faster than conventional computers can.

Perhaps the best known of these tasks is factoring a large number that is the product of two primes. Multiplying two primes is a simple job for computers, even if the numbers are hundreds of digits long, but the reverse process—deriving the prime factors—is so extraordinarily difficult that it has become the basis for nearly all forms of data encryption in use today, from Internet commerce to the transmission of state secrets.

   
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