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Previously in Digital Culture:

"Bugged," by Charles C. Mann (March 15, 2000)
We survived the Millennium Bug. But just because we're no longer threatened by bad software from the 1960s, it doesn't mean we're safe from all the bad software of the 1990s.

"Alternate Realities," by Harvey Blume (January 13, 2000)
Choose your technorealism. William Mitchell's e-topia and Douglas Rushkoff's Coercion take starkly differing views of the Information Age. Plus, interviews with both authors.

"The Unacknowledged Legislators of the Digital World," by Charles C. Mann (December 15, 1999)
In his new book, Code and Other Laws of Cyberspace, Lawrence Lessig offers a disconcerting vision of the Net's future. Too disconcerting, objects our reviewer. Plus, an e-mail exchange between Lessig and Atlantic Unbound editor Wen Stephenson.

"Exquisite Source," by Harvey Blume (August 12, 1999)
Heads turned in June when the Linux operating system was awarded first prize by the judges of an international art festival. How far, one wonders, can the open source model go?

"With Liberty and Justice for Me," by Mark Dery (July 22, 1999)
Is the Internet giving ordinary people more control over their lives? An e-mail exchange with Andrew L. Shapiro, the author of The Control Revolution.

"Bits of Beauty," by Harvey Blume (June 3, 1999)
Yes, it's art. Now what is there to say about it? An assessment of the first-ever Cyberarts Festival in Boston, where art criticism is forced to play catch-up with technology.

See the complete Digital Culture index.

More on Technology and Digital Culture in Atlantic Unbound and The Atlantic Monthly.

Discuss this article in the Technology & Digital Culture conference of Post & Riposte.

Reimagining the Cosmos

Through the quest for a quantum computer -- described in Julian Brown's new book, Minds, Machines, and the Multiverse -- much is becoming clear about the strange, paradoxical world governed by quantum mechanics. Will it change the way we think about our universe (or multiverse)?

by Harvey Blume

May 3, 2000

Quantum mechanics -- the study of subatomic waves and particles -- has a proven ability to excite and disturb the imagination. Einstein strenuously and vainly objected to the probabilistic side of quantum physics -- the fact that at the quantum level, there were no sure things, only odds. God, he protested, could not possibly run the universe like a game of dice. But judging by the Broadway success of Michael Frayn's play Copenhagen, in which Werner Heisenberg, the founder of quantum mechanics, expands on the implications of his uncertainty principle, the public is fascinated by the very games of quantum chance Einstein inveighed against.

Once quantum computing approaches the threshold of practicality, which it shows increasing signs of doing, quantum mechanics will draw an even broader public. Two years ago, physicists and computer scientists knew that for certain kinds of applications quantum computers would be far superior to conventional machines, but they couldn't be sure that the practical difficulties of building such devices could be overcome. Then, in the spring of 1998, MIT's Neil Gershenfeld and several other physicists built a three quantum bit (qubit) device, which was topped, this past spring, by Ray LaFlamme, who demonstrated a seven qubit computer. The qubit is the smallest unit of quantum computing, and in principle can consist of anything, from the magnetic field of an atomic nucleus to the spin of a photon, that exhibits quantum properties. Seven qubits, to be sure, is still shy of a qubyte, but it gives researchers greater confidence that quantum computing has a future outside the laboratory.

In his new book, Minds, Machines, and the Multiverse: The Quest for a Quantum Computer, the science writer Julian Brown traces the evolution of quantum computing and describes the kinds of questions it forces both physicists and computer scientists to confront: Is the universe itself a kind of quantum computer? Are physics and computer science, in other words, only different ways of describing the same phenomena? What are quantum logical gates and how can they be assembled out of famously unstable subatomic events? Brown tackles such questions in detail. The fact that the book is relatively free of math does not mean that it's free of conceptual difficulty -- this is not quantum computing for dummies, if there can be such a thing. As much as anything else, the book is an investigation of the views of the physicist David Deutsch, a founder of quantum computing who believes its main effect will be to force a philosophical change on our culture.

Quantum computing reverses some core assumptions of conventional computing. We take for granted, for example, that the logic of conventional computers is hardwired into their processors. But in the most popular method of quantum computing to date, logic comes from without, in the form of radio waves that align and manipulate the nuclei of computing material. Because the logical complexity is contained in the radio waves, the computing material itself can be very simple -- a thimbleful of chloroform has sufficed for one of Neil Gershenfeld's experiments, and there has been recent talk of a cup of coffee serving as a quantum computer, talk which should not be taken as hyperbole. It may be that in the end a quantum computer will look less like the laptop or hand-held devices we're used to than like a searchlight, moving through the natural world and highlighting quantum phenomena as it goes. And quantum computing will be blazingly fast, tearing through problems, such as the factoring of huge numbers, that take conventional computers years, if not eternities, to solve. Since today's best computer encryption schemes depend upon the difficulty of factoring very large numbers, it's not hard to see why the race is on for the quantum computer: in the eternal game of cryptographic thrust and parry, it may well be that only a quantum computer can perfect a code other quantum computers won't be able to crack.

But there's a price to pay for quantum power. It's one thing to concede that subatomic processes are governed by the bizarre set of paradoxes and probabilities known as quantum mechanics. It's another thing to get a decent day's -- or second's -- work out of such paradoxes and probabilities. The genie in the quantum coffee cup will agree to factor 500-digit numbers in a flash (a feat from which all of today's computers would shrink), but only at the expense of wreaking havoc on our traditional notions of the cosmos. For David Deutsch, as profiled by Julian Brown, cosmological havoc is exactly the point, and factoring large numbers only a means toward that end. As Deutsch sees it, it will take nothing less than a new cosmology to encompass the truths of quantum mechanics. In effect, what Deutsch proposes is a trade-off; he intends to make quantum mechanics a little easier on the human mind by making cosmology more complicated. To see how this is so, it would be useful to look at the basic building block of quantum computing, the qubit.

Qubits differ from conventional bits in that they can hold more than one value at a time. A single conventional bit can be zero or one. A qubit can be zero and one. Eight conventional bits can represent any value between zero and 255. Eight qubits can store every value between zero and 255 simultaneously, or in parallel. As you increase the number of bits, the advantages of qubits become ever more pronounced.

The all-at-onceness of quantum phenomena, as exhibited by the qubit, is one of their peculiarities. So, too, is the fact that at quantum level supposed particles often simply cannot desist from acting like waves. This tendency can be illustrated by an experiment which we can perform, to start with, using baseballs. Suppose you're on the mound facing not a batter, but two holes in a wall. You've got excellent control, and pitch through one or the other of the holes every time. Now assume you're suddenly a whole lot smaller, and instead of baseballs you're firing photons. To your surprise, every pitch goes through both holes simultaneously, as it would if you were somehow hurling waves rather than discrete particles.

The Multiverse Pitch by Sage Stossel

Quantum phenomena can have multiple values simultaneously or be in many places at the same time, until the magic moment when they are actually measured, at which point they are said to decohere, or collapse, into a single value. Why quantum phenomena have many values at one point and forgo all but one of those values at the moment of measurement generates endless debate and no little amount of confusion. Can consciousness really have this kind of determining effect on reality? Are quantum phenomena like unruly kids who invariably manage to materialize in their seats at the precise moment when the teacher reenters the room? Most interpretations have to include some version of consciousness and measurement as the final arbiters of a subatomic melée, which compels some physicists to abjure efforts at interpretation altogether.
This is where David Deutsch's "many-world," or multiverse, interpretation comes in. Deutsch believes that when quantum phenomena appear to be absurd, they are absurd. It's not the human mind that's at fault, only our current model of the cosmos. No, a photon can't go through two holes simultaneously, which it appears to do in the two hole experiment -- at least not in a single universe. Eliminating the impossible, like Sherlock Holmes, Deutsch comes to the only remaining conclusion (if, indeed, it's any less impossible): he reasons that there must be more than one universe involved. When the photon appears to be in two places at the same time, we're really encountering an infinitesimal overlap of worlds, in each of which the photon behaves normally enough, passing through only one hole at a time. Writers who explore the notion of parallel universes -- like Jorge Luis Borges in his story "The Garden of Forking Paths" -- would find only reinforcement in Deutsch's view of quantum mechanics. In the multiverse, what we perceive as quantum weirdness is the residue of the never-ending bump and grind of worlds that may differ at one instant by nothing more than the direction of a photon, which will be enough to send them hurtling down incalculably different evolutionary paths.

For Deutsch, the great marvel of quantum computing is that it harnesses the power of the multiverse. As he puts it in his book, The Fabric of Reality: The Science of Parallel Universes -- and Its Implications (1997), quantum computing is "the first technology that allows useful tasks to be performed in collaboration between parallel universes." In Minds, Machines, and the Multiverse, Julian Brown quotes Deutsch as saying that the importance of quantum computing is that it uncovers
a deep and unsuspected connection between physics and computation. Computation is connected to all sorts of human things like thought, knowledge, life and so on, whereas physics is the most fundamental description of nature. So here we have an unsuspected, very deep connection between human-type things and fundamental-type things. I think philosophy is going to take a long time to assimilate this.
And not only philosophy -- physics, too. In his book The Life of the Cosmos (1997), the physicist Lee Smolin writes of the multiverse that, "I must confess immediately that I do not like it" and expresses puzzlement that such distaste is not widespread in his profession. John Horgan, the author of The End of Science (1997) and The Undiscovered Mind: How the Human Brain Defies Replication, Medication, and Explanation (1999), specifies the multiverse view as a prime example of what he labels "ironic science"-- or "science that never gets a firm grip on reality and thus does not converge on the truth." The physicist Neil Gershenfeld likewise disowns Deutsch's view, writing, "[The multiverse], and many related ideas, are wonderful, but also not falsifiable. I find that trying to add explanations to the formalism of quantum mechanics stretches our language and search for intuition far beyond where they belong."

Though he doesn't take the implications of quantum computing as far as Deutsch, no one has done more than Gershenfeld to popularize some of the other notions so dear to Deutsch, especially the idea that quantum computing uncovers similarities between the laws of physics and the laws of computation. In the views of both scientists, nature is already a computer; the trick -- and the key to quantum computing -- is to know how to interface with it.

We are at a stage in computing today that may, for all its seeming hyperactivity, be remembered as a kind of lull in the history of computation. All computing to this point has shared in certain basics of design and material. Some combination of silicon, copper, and several other materials suffices for all our conventional machines, just as the rules of Boolean algebra (a formalized extension of Aristotelian logic) suffice to put those machines through their paces. But as we approach the point, in the next decade or two, where Moore's Law (according to which computing power doubles every eighteen months) cannot be obeyed by conventional means, the very stuff of computation will begin to diversify. For some tasks there may well be DNA computers, for others, optical and holographic computing. And, of course, there are the beginnings of quantum computing, which operates according to rules that can never be mistaken for Aristotelian logic (just try and tell a qubit it can't be A and not-A at the same time).

Quantum computing may jump very quickly from being little more than a physicist's daydream, a mathematical cum philosophical thought experiment, which is the position it occupied until very recently, to being an indispensable part of our lives. David Deutsch is right to think this can only mean that all kinds of cosmological issues will escape from quantum confinement. Quantum mechanics has proven to be a catalyst to the literary, as well as the scientific, imagination. In his novel, Eating Pavlova (1995) D. M. Thomas has a character recall an encounter between Wolfgang Pauli and Neils Bohr, two of the founders of quantum physics, in which "Pauli had expounded some new idea in quantum physics -- I believe in fact it was the concept of multiple, universal coitus first touched upon by the Kabbalists -- and Bohr leapt to his feet exclaiming: 'It's not crazy enough! It can't be right!' And Pauli snarled in reply: 'It is crazy enough!'" Who could deny that multiverse is crazy enough? But thoughts of it may soon be as commonplace as the smell of coffee.

Discuss this article in the Technology & Digital Culture conference of Post & Riposte.

More on Technology and Digital Culture in Atlantic Unbound and The Atlantic Monthly.

Harvey Blume is a contributing writer for Atlantic Unbound and The Boston Book Review.

Illustration by Sage Stossel.

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