What a gentle title for such a serious subject! George Johnson, who writes about science for the New York Times, published recently a book named "A Shortcut Through Time: The Path to the Quantum Computer." (Here is a review by Scientific American, "The Next Big Thing?")
Now he wrote an article in plain english about quantum computing for TIME Magazine. Here are some quotes.
In the latest of a steady stream of small developments, researchers in the Netherlands and Japan reported in the journal Science last week that they had caused an electrical current in a superconducting ring to flow simultaneously clockwise (representing 1) and counterclockwise (0). The result was a "qubit," a quantum representation of both the digits of binary arithmetic. In other labs, qubits have been devised from single atoms. Whatever is used as the quantum abacus beads, the result is an exponential explosion in computing power.
Ordinarily a row of 10 bits (think of them as tiny switches turned on or off) can hold any one of a thousand different numbers (1,024 to be exact). But a row of 10 qubits, because of its quantum nature, can hold all the numbers at once. To find the square root of every number from 1 to 1,000, you would load them all onto a row of 10 atoms, perform a single calculation, and -- voila -- all the answers would appear.
Every time you add a qubit to the string, the computing power doubles. A row of 11 atoms will carry out 2,048 simultaneous calculations, and a row of 12 will do 4,096. By the time you get to just 14 atoms, a speck still far too tiny to see, you can do more calculations in tandem (16,384) than the fastest supercomputer in the U.S. -- a machine at Los Alamos National Laboratory so voracious that it draws several megawatts of power.
How far are we from real quantum computers?
Of course, what is true in theory may turn out to be impossible in practice. As one researcher, Lov Grover of Lucent, put it, "We're writing the software for a device that does not yet exist."
Though nothing in the laws of physics rules out quantum computers, qubits are maddeningly delicate. Experiments must be done at temperatures near absolute zero, and the slightest disturbance can cause the teetering quantum states to collapse.
Source: George Johnson, for TIME Magazine, February 18, 2003
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