NYTimes.com Article: Harnessing Atoms to Create Superfast Computers

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Here's another review of "Shortcut through time", George Johnson's book on quantum computing.


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Harnessing Atoms to Create Superfast Computers

March 7, 2003
By IAN FOSTER




 

George Johnson's "Shortcut Through Time" addresses one of
the most excruciatingly complex, mysterious and deeply
fascinating topics in modern science, namely quantum
computing: the manipulation of quantum states to perform
computations far faster than is possible on any
conventional computer. The book's remarkable achievement is
that it makes this deeply arcane topic accessible and
understandable - even, I think, for the reader
unsophisticated in physics or computing. It opens a door to
broader understanding of this important field and sets a
new standard for science writing.

I was originally reluctant to review this book. I am a
computer scientist with a guilty secret: I've never really
understood quantum computing. How could I write a review
without revealing my ignorance?

However, as I began the preface, I became intrigued and
then excited. Mr. Johnson, a contributing science writer
for The New York Times, says he wrote the book not to
profile the personalities in the field, but to lead the
reader toward a tentative understanding of quantum
computing. To take the reader along as he, the writer,
strains "to grasp an idea with an imprecise metaphor, only
to discard it for another with a tighter fit, closing in on
an airy notion from several directions, triangulating on
approximate truth." And: "I want the reader to feel that we
are both on the same side - outsiders seeking a foothold on
the slippery granite face of a new idea."

I was hooked. So much of what passes for science writing
nowadays is really human-interest journalism, focused on
the quirks and conflicts of science's eccentric
personalities, and is only incidentally concerned with
science itself. Yet here was someone who proposed to take a
problem at the forefront of science and address it on its
own terms. Perhaps my ignorance was a virtue: I could serve
as an experimental subject, reading the book and reporting
on whether I arrived at the promised land.

Approached from this perspective, the book took on the
allure of a good mystery. Mr. Johnson, like a seasoned
crime writer, sets the scene and then introduces a series
of increasingly intriguing metaphors, each of which unveils
another aspect of Q.C., as I'll call it. As the story
unfolds, it becomes clear that Q.C.'s secret could be
revealed at the turn of any page. For me, the initial
forays covered familiar ground. But Mr. Johnson soon
entered unfamiliar territory, exploring the mysteries of
superposition and entanglement.

Along the way, we discover that we are dealing not with an
obscure and eccentric academic curiosity, but with a
dangerous character. (In addition to mystery, we have
drama!) Q.C., it has been shown in the last few years,
could defeat some of the fundamental codes that secure many
electronic communications. The security of these public key
cryptography mechanisms relies on the fact that on even the
fastest computers, performing a particular computation -
factoring, or breaking into their constituent pieces, large
numbers - takes an unimaginably long time. Yet in 1994
Peter Shor, a mathematician, showed how Q.C. could do this
same operation much faster - in a few minutes. Q.C. could
provide a shortcut through time.

Just why this is possible is at the heart of this concise
but dense book. The particulars depend on the clever
manipulations of two fundamental properties of the quantum
world - superposition and entanglement. Superposition lets
a single quantum switch be on and off at the same time;
entanglement allows the state of one quantum switch to be
linked with that of another. Set up just right, a
collection of such quantum switches can, in principle, be
used to build a computer that manipulates many numbers at
once - transforming millions of numbers in one step, or,
via mind-numbingly complex manipulations, factoring the
numbers that support our financial and national security.

Fortunately for those who use codes to maintain secrets, we
also learn that Q.C. does not exist yet, at least not in a
useful form. As Mr. Johnson notes, the world record for
building a quantum computer involves just seven qubits
(quantum switches, pronounced like the word cubits)
operating for less than a second. A quantum computer with
several thousand qubits and able to run for hours is not
expected anytime soon. The problems involved in scaling up
are complex and hard to resolve. They relate to the
tendency of superposed quantum states to collapse to a
single value - either on or off - when the real world
impinges.

"A Shortcut Through Time" is not all metaphor. It also
touches on the history of this young field, noting a
prescient paper by the physicist Richard P. Feynman, who
postulated in 1982 that quantum computing might be
possible. (Also mentioned is the independent work by a less
famous but just as visionary physicist, Paul Benioff,
formerly of the Argonne National Laboratory.) But what
makes this book a delight and a rare gem of science writing
is the science itself, and Mr. Johnson's engagement with
that science. He promises that he is not going to cheat by
implying omniscience with his subject), and he does not.
The result is fascinating and tremendously engaging.

After all this, you may be wondering whether I now
understand quantum computing. Well, there are some who
argue that quantum physics is so foreign to human
experience that no one can truly understand it, only
manipulate its mathematical rules. Mr. Johnson does not use
mathematics and he skips many details. ("We are operating
here on a need-to-know basis," he states.) But I found that
with him at my side, I could reach that delicate mental
state that feels like understanding. Now this state, like a
quantum superposition, may collapse to ignorance when I try
to explain it to someone, but in the meantime, I feel less
guilty.

Ian Foster is a senior scientist at Argonne National
Laboratory and a professor of computer science at the
University of Chicago.

http://www.nytimes.com/2003/03/07/books/07BOOK.html?ex=1048138180&ei=1&en=c9ea4623df5595d0



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