This is not Schrödinger's Cat
From Quartz:
For the past several years, a Canadian company called D-Wave Systems has
been selling what it says is the largest quantum computer ever built.
D-Wave’s clients include Lockheed Martin, NASA, the US National Security
Agency, and Google, each of which paid somewhere between $10 million
and $15 million for the thing. As a result, D-Wave has won itself
millions in funding and vast amounts of press coverage—including,
two months ago, the cover of Time (paywall).
These
machines are of little use to consumers. They are delicate, easily
disturbed, require cooling to just above absolute zero, and
are ruinously expensive. But the implications are enormous for heavy
number-crunching. In theory, banks could use quantum
computers to calculate risk faster than their competitors, giving them
an edge in the markets. Tech companies could use them to figure out if their code is bug-free.
Spies could use them to crack cryptographic codes, which requires
crunching through massive calculations. A fully-fledged version of such a
machine could theoretically tear through calculations that the most
powerful mainframes would take eons to complete.
The
only problem is that scientists have been arguing for
years about whether D-Wave’s device is really a quantum computer or not.
(D-Wave canceled a scheduled interview and did not reschedule.) And
while at some level this doesn’t matter—as far as we know, D-Wave’s
clients haven’t asked for their money back—it’s an issue of importance
to scientists, to hopeful manufacturers of similar machines, and to
anyone curious about the ultimate limits of humankind’s ability to build
artificial brains.
The processor at the heart of the controversy.
D-Wave Systems
Quantum computers: a grossly oversimplified introduction
The
foundation of all computing is a logic gate—a simple yes/no switch. In
modern computers, one position of the switch represents 0; the other
represents 1. Your laptop computer contains billions of such gates, each
of which switches between 1 and 0 billions of times a second.
Nonetheless,
your computer has a handicap, imposed by classical physics. At any
given moment it can only be in one state—one particular combination of
1s and 0s across those billions of gates. It has to step through a
sequence of such states to complete a calculation. But what if, instead,
a vast number of copies of your computer could somehow exist in
parallel, each representing one of these possible states,
and collectively perform the entire calculation simultaneously?
Essentially,
this is what quantum theory says can happen. The key is to shrink the
gates small enough that quantum physics, which describes the behavior of
extremely small objects, takes over from classical physics. (Some
quantum gates consist of a single atom, held in place by electric and
magnetic fields.) Such a tiny gate, called a “qubit,” can exist as a
kind of combination—called a “superposition”—of 1 and 0. A computer made
of qubits would, in some sense, exist in all the possible
combinations of 1s and 0s at once.
Physicists
differ in how they interpret this. Some literally believe a myriad
parallel universes exist, each containing a separate copy of
the computer; some have a more minimalist explanation. But the outcome
is the same: In principle, it’s possible to reap the fruits of all that
parallel processing to arrive at a result faster—so much faster that
even the hardest calculation could become pretty much instantaneous.
(For more details in something resembling English, see this interview with MIT’s Scott Aaronson—a long-time skeptic of D-Wave—in the Washington Post, this excellent blog post by Michael Nielsen, and, thus prepared, this Reddit thread.)...
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"Baa baa Schrödinger's sheep, have you any wool?
Yes sir, no sir, three bags simultaneously full and empty"
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