« SAW leather tote bag | Home | Denim Mobile Phone Case »

May 1, 2011

Quantum computing in many worlds

The May 2, 2011 issue of the New Yorker contains what I think is the single most lucid article I've ever read about quantum theory, quantum computing, and the Many Worlds hypothesis.

Props to Rivka Galchen, the author.

Alas, the piece is hidden behind the magazine's subscription wall, so you're going to either have to make do with the excerpts below or go find a copy and read it yourself.


On the outskirts of Oxford lives a brilliant and distressingly thin physicist named David Deutsch, who believes in multiple universes and has conceived an as yet unbuildable computer to test their existence.

With one millionth of the hardware of an ordinary laptop, a quantum computer could store as many bits of information as there are particles in the universe.

Deutsch's belief that if a quantum computer were built it would constitute near irrefutable evidence of what is known as the Many Worlds Interpretation of quantum mechanics.

England, where the intense interest in quantum computing has at times been termed the Oxford flu.

Physics advances by accepting absurdities. Its history is one of unbelievable ideas proving to be true.

Even to physicists, quantum mechanics — the basis of a quantum computer — is almost intolerably odd.

Quantum mechanics describes the natural history of matter and energy making their way through space and time.

In quantum mechanics, the universe, at its most elemental level, is random, an idea that tends to upset people.

If classical mechanics is George Eliot, quantum mechanics is Kafka.

Said Deutsch, "To say that prediction is the purpose of a scientific theory is to confuse means with ends. It is like saying that the purpose of a spaceship is to burn fuel."

A classical computer — any computer we know today — transforms an input into an output through nothing more than the manipulation of binary bits, units of information that can be either zero or one. A quantum computer is in many ways like a regular computer, but instead of bits it uses qubits. Each qubit can be zero or one, like a bit, but a qubit can also be zero and one — the quantum-mechanical quirk known as superposition.

Superposition is like Freud's description of true ambivalence: not feeling unsure, but feeling opposing extremes of conviction at once. And, just as ambivalence holds more information than any single emotion, a qubit holds more information than a bit.

A quantum computer is the pot that, if watched, won't boil. Charles Bennett described quantum mechanics as being "like the information of a dream — we can't show it to others, and when we try to describe it we change the memory of it."

For Deutsch, to really understand the workings of a quantum computer necessitates subscribing to Hugh Everett's Many Worlds Interpretation of quantum mechanics..., which entails the following counterintuitive reasoning: every time there is more than one possible outcome, all of them occur.

The quantum computer's processing power would come from a kind of outsourcing of work, in which calculations literally take place in other universes.



May 1, 2011 at 02:01 PM | Permalink


TrackBack URL for this entry:

Listed below are links to weblogs that reference Quantum computing in many worlds:


may 2, 2011

Posted by: rob | May 2, 2011 6:57:17 PM

J.J. Abrams just sent a cease and desist through the Walternet.

Posted by: 6.02*10^23 | May 2, 2011 1:47:21 PM

The comments to this entry are closed.