Silicon is Slow

But that would require a quantum computer with hundreds of thousands of qubits-and even the most optimistic researchers say that such systems are at least 15 years away. In fact, Chuang doesn't envision getting much beyond 10 to 20 qubits with his current scheme, because the magnetic signals that measure the direction of the spins-and determine whether the qubit is 1, 0, or both-grow fainter as the number of qubits increases. So researchers are exploring other technologies, such as encasing qubits in solid-state "cages" and reading them with lasers. "Nobody in this field understands what's going on," admits Chuang with a laugh. "Quantum physics defies our intuition."


Many scientists still believe that nanocomputers will be limited to highly specialized applications such as cryptography or database searching. There's precedent for such conservatism: The room-size ENIAC was originally built to calculate the trajectory of artillery shells, and at around the same time IBM chairman Thomas Watson made his famous remark about there being a world market for perhaps five computers. IBM and its successors have drummed up a few more uses for computers since then; nanocomputers are likely to experience a similar fate. If the computer revolution of the past half-century is any indication, as the machines continue to get smaller, the possibilities will only grow.


Looking Back: More Brawn Than Brains
Popular Science's reporting on computers began in the 1940s, with the first room-size behemoths such as the Mark I and II, ENIAC, and MIT's 100-ton "electro-mechanical differential analyzer." At right is the "intricate, bedspring-like maze of wiring" from Mark II, built in the Harvard Computation Lab. Early coverage enthused over speeds that desktop computers now easily surpass. In January 1946 we said of MIT's monster computer:


"In a few minutes, or in a few hours at most, this giant calculating machine provides answers to complex problems it would have taken trained men weeks to solve.


Able to tackle three problems at a time, with as many as 18 variables in any one, the calculator contains 200 miles of wire, 2,000 electronic tubes, several thousand relays, and about 150 motors. Yet, despite its apparent vast complexity, one man can operate it."