The quantum for those that dont believe in organisms

D.Murali


Any computer should be able to do two things: store information in the form
of bits (0s and 1s), and offer a way to alter the bits in accordance with
instructions (using logic gates. Thus writes Vishal Sahni in Quantum
Computing ( www.tatamcgrawhill.com).

“Everything a computer does — whether synthesising speech, calculating the
billionth digit of pi or beating Garry Kasparov at chess — ultimately comes
about through the transformation of bits by gates,” he explains.

“Could subatomic particles store bits? Could they form gates?” To find
answers to these questions, you need to enter the world of quantum
computers, which operate according to the rules of quantum mechanics
governing ‘the world of the very small: the waves and particles of subatomic
physics’.

A startling discovery of twentieth century physicists that gave ‘enormous
incentive to apply quantum mechanics to computing’ was that elementary
particles such as protons, neutrons, and electrons could exist in two or
more states at once, the author narrates.

Conventional electronics has depended on the advancements in miniaturisation
and the pronouncement by Gordon Moore (that performance per unit cost
increases by a factor of two every 18 months). How long can Moore’s law
continue to hold, the author asks? “Can we continue to expect an exponential
improvement in performance 20 or more years from now?”

Perhaps, quantum computing is the alternative. Quantum computers are still
in labs, but researchers are never tired of describing the possibilities.

“We are writing the software for a device that does not yet exist. Yet, on
paper, the prospects are stunning,” says Sahni.

Scenarios include: “An algorithm that could factor 140-digit-long numbers a
billion times faster than is currently possible… a search engine that could
examine every nook and cranny of the Internet in half an hour, a brute-force
decoder that could unscramble a DES (data encryption standard) transmission
in five minutes…”

Well, a home quantum computer is among ‘five ideas that will reinvent
computing’, according to PC Magazine. The other ideas are IMAX-quality
movies at home with new projectors, a mid-air mouse that requires no flat
surfa ce, a router-based peer-to-peer system, and a man-made brain, as a
recent posting on http://it.slashdot.org states.

The fundamental unit of information in quantum computing is qubit, short for
quantum bit. “A qubit can exist not only in a state corresponding to the
logical state 0 or 1 as in a classical bit, but also in states corresponding
to a blend or superposition of these classical states.” For 500 particles,
say, we could create a quantum system that is a superposition of as many as
2 to the power 500 states, explains Sahni. “With one machine cycle, one tick
of the computer clock, a quantum operation could compute not just on one
machine state, as serial computers do, but on 2 to the power 500 machine
states at once.”

As a result, quantum computers would be able to solve problems that
classical computers cannot touch. “If functioning quantum computers can be
built, harnessing their potential will be just a matter of creating
algorithms that carry out the right operations in the right order.”

Ready for the ‘quantum’ leap?