Re: Design (was: Oh piss off *spoilers*)

"solar penguin" <solar.penguin@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
wrote in message news:43fa4282$1_4@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx

Yads said:

solar penguin

Yads said:


Design has to ordered so that everything can hold in position.

But not everything _does_ hold in position, does it? What about the
Heinseberg and all that quantum weirdness? The particle goes through
both slits _at the same time_. It doesn't even have a proper
position to hold into!


Ever heard of error?

There's no error in that slit experiment. The particle really _does_ go
through both slits at once. That's a fact, not an error. It's all
because randomness really exists, like Manky Badger said in another
branch of the thread. The randomness prevents the world from being
truly ordered.

Though the latest findings about quantum theory in recent issues of New
Scientist show a deeper determinism is actually at work... one example:

Discovering the true nature of reality
a.. 18 June 2005
b.. From New Scientist Print Edition. Subscribe and get 4 free issues.
c.. Mark Buchanan
WHAT keeps Nicolas Gisin pressing on with his experiments? He goes to
extraordinary lengths to fire photons beneath the waters of Lake Geneva,
sending them through fibre-optic telephone cables from his lab at the
University of Geneva to another lab some 25 kilometres away. And time after
time his results prove what we have known for nearly a century: that quantum
theory makes good predictions about the properties of particles like Gisin's
photons. Why does he bother?

Over the past decade, Gisin and his colleagues at the university have been
probing the peculiar features of quantum entanglement, the way the
properties of two or more particles can become invisibly linked, even if
they become separated. Do something to one, and quantum theory says that the
other should be affected instantaneously. Gisin's experiments and those of
many others certainly seem to show the effect is real. But if they have
proved that, what's the point of carrying on? Well, says Gisin, something
rather surprising is emerging from their results.

If Gisin's experiments can be trusted - and most physicists believe they
can - and quantum theory is right, then basic logic says there is something
fundamentally wrong with our view of the universe. It would be good news for
quantum theory, but bad news for some of our deepest preconceptions about
the nature of reality. "Either space-time is an illusion," Gisin says, "or
free will is an illusion."

But it may be more profound still. There is a third option, favoured by
several physicists who have looked at Gisin's work: that the laws of nature
may somehow conspire to keep quantum theory's strangest predictions from
ever coming true, and that understanding why may point physicists toward a
deeper theory from which quantum rules emerge. So you can begin to see why
Gisin is still firing photons around Switzerland. "This," he says, "is one
of the most important questions in physics."

Quantum entanglement has long produced as many questions as answers.
Consider electrons, which have a quantum property called spin, which is
always either "up" or "down", along whichever direction you might choose to
measure it - along the vertical, for instance, or east-west. When an
experimenter creates two entangled electrons, they will have opposing spins:
if one is up, the other is down. But the experimenter can also create
entangled pairs of electrons with undefined spins. In this case each
particle's spin is a peculiar superposition of up and down at the same time.

And this is where entanglement creates some seriously strange phenomena.
Quantum theory predicts that the value of either particle's spin only
becomes definite if you measure it. But if you measure the spin of one
electron and find it to be up, say, that will instantaneously trigger the
spin of the other electron to become definite as well, and point down.

Strange though it is, this prediction of quantum theory has survived test
after experimental test. The most rigorous of these are based on theoretical
work published in 1964 by physicist John Bell of CERN, the European particle
physics lab near Geneva. Stimulated by an earlier thought experiment by
Albert Einstein, Bell imagined an experiment in which you separate entangled
pairs of electrons and send them to very distant places. Experimenters at
these far apart locations could then measure their particles' spins at the
same time. What would they find?

Bell calculated the outcome based on three assumptions. First, that the two
experimenters could freely choose to measure the spins using any axis they
like. Second, he assumed that there is something about each electron, before
it is measured, that helps determine what is likely to happen in a
measurement; that is, the experimental results reflect some real,
pre-existing property of the particles and their local environment. And
third, that no influence can travel faster than light, so if the
measurements take place at virtually the same time, what happens at one end
cannot possibly affect what happens at the other.

Bell showed that, if these seemingly plausible assumptions hold true,
certain experiments would flout the predictions of quantum theory. In
mathematical terms, the three assumptions lead to a "Bell inequality"
relating the outcomes of various experimental tests, whereas quantum theory
says that the inequality is violated; in other words, if quantum theory
holds, at least one of the assumptions must be wrong.

Many of the experiments testing Bell's scenario use photons rather than
electrons, but the logic is the same. In an experiment last year, for
example, Gisin and colleagues created pairs of entangled photons, and sent
each member of the pair in opposite directions along 25 kilometres of
fibre-optic cable.

In this case the entanglement didn't involve spin, but rather the precise
timing of the photons. Just as an electron's spin can be up or down, the
photons produced by the team's apparatus could be "early" or "late", pushed
forwards or backwards relative to some average time of arrival. Repeating
the test for millions of photon pairs, Gisin and colleagues found that they
acted just as quantum theory says they should, violating Bell's inequality
(Physical Review Letters, vol 93, p 180502).

At the University of Illinois at Urbana-Champaign, physicist Paul Kwiat and
colleagues have just finished another experiment using photons and found
similar results. "We've found some world-record violations," Kwiat says. His
experiments violate Bell's inequality by more than 1000 standard deviations
(where one standard deviation is the typical amount of random scatter).
Clearly that's not likely to be the result of chance.

In every test, over more than two decades, quantum theory has come out
intact. So relativity's assumption that nothing can travel faster than the
speed of light is flawed... or is it? Well, not necessarily: there are two
other assumptions that have to be tested first.

The first is free will. Bell's analysis only produces his inequality if the
two experimenters have genuine freedom to choose how they set their
detectors. In an experiment with spins, that means being able to make
measurements along axes that they can choose independently. But maybe that
isn't possible. "The idea is that everything could be somehow determined at
the beginning," says Gisin. Perhaps the creation of the particle pairs and
the experimenters' choices are fixed by a vast web of cause and effect set
up long ago, in which case the "choices" would be predetermined and beyond
anyone's control. Some fundamental law might mean that these choices always
lead to a violation of Bell's inequalities.

Unsurprisingly, not many physicists go for this idea. So what of the other
assumption behind the inequality?

Bell's analysis requires that reality is "out there" and has properties even
when we don't measure them. Rejecting this is another way to explain how it
is that experiments seem to violate his inequality. It could be that prior
to being measured, a quantum particle has no property that makes
measurements come out one way rather than another (New Scientist, 24 July
2004, p 30). Physicists do experiments and get results - lines on some
photographic film, settings on a dial. Quantum theory describes these
outcomes with perfect accuracy, but that is all there is to say.

That's not as outrageous as it might seem - many physicists subscribe to
this view. "Quantum theory isn't a description of physical reality," is how
the late physicist Asher Peres at Technion, the Israel Institute of
Technology, put it. "All it does is provide correct answers to meaningful
questions about experiments."

But many other researchers find this casual attitude toward reality less
than satisfactory. "This philosophy certainly abolishes the paradox," says
mathematician Richard Gill of he University of Utrecht in the Netherlands,
"but to my mind hardly explains it." Gill and many others argue that reality
simply must have properties that are independent of our decision to measure
them, otherwise science is based on nothing concrete. As Einstein once said,
it's hard to believe that the moon isn't there when we don't look at it.

So, if we are satisfied that experimenters have free will and that reality
has its own properties, we return to our original suspect, Gisin says. It
seems entanglement allows distant parts of the universe, light years apart,
to be linked up in a decidedly strange way. Some kind of influence appears
to be travelling faster than light, and Gisin has even done experiments that
put a lower limit on the speed of that weird influence (see "How much faster
than light?").

These faster-than-light links can't be used for transmitting information,
because they are based on random outcomes and so are uncontrollable. But
this could still mean that relativity, Einstein's famous description of
space and time, is ripe for redrafting. After all, something has to give,
and better relativity than human free will.

"Entanglement is a new explanation for how things happen in the universe,"
Gisin says. "It's on the same conceptual level as cause and effect: there's
cause, effect and entanglement."

Loopholes
The results are still not quite clear-cut enough to entice all physicists to
take this plunge, though. The dissenters suspect that it's quantum theory
that has something missing. Although a number of experiments have now found
violations of Bell's inequality - and made sure that only faster-than-light
signals could have passed between the particles during the window of
measurement - these experiments all suffer from an Achilles' heel thanks to
the imperfection of particle detectors.

In their most recent experiment at Lake Geneva, for example, in only about 1
per cent of photon pairs were both photons detected. While these detected
pairs followed quantum theory, violating Bell's mathematical condition, it
is possible that they didn't give a fair picture. Maybe the pairs that
weren't detected would have proved quantum theory wrong.

Four years ago, physicist Dave Wineland and colleagues from the National
Institute of Standards and Technology in Colorado managed to close the
detection loophole in an experiment using ions held in traps. But the catch
was that the ions were so close together that the researchers couldn't make
their measurements quickly enough to ensure that any influence travelling
between the ions would have had to move faster than light.

"Eventually the ions might be able to do the job," says Wineland, "but
they'd have to be separated by at least 30 kilometres, currently a tough
proposition." Kwiat hopes to close the loophole in the photon experiments by
building better photon detectors, perhaps with efficiencies approaching 90
per cent, but this too appears to be some years off.

And so as physicist Emilio Santos of the University of Cantabria in Spain
argues, it looks like the jury will be out until someone does an experiment
that closes the loophole completely. "Most people think that the Bell
inequality has been violated," he says, "but this is misleading and in my
view harmful for the progress of science."

Santos might have a point: nature has surprised physicists many times in the
past, and perhaps we shouldn't be so quick to decide how experiments will
"obviously" turn out. Physicist Ian Percival of Queen Mary, University of
London, for example, speculates that a definitive loophole-closing
experiment might be impossible as a result of some as yet unknown law of
nature. This law might make it impossible to create some of the situations
that quantum theory technically allows - and in particular those that would
violate the Bell inequality - without leaving loopholes.

Percival suggests that if such experiments are impossible, then
faster-than-light influences may be impossible too, and what Gisin is seeing
is a mirage created by the open loopholes. Percival isn't claiming that this
is the case, merely pointing out that logic suggests it as a possibility.
Gill agrees. "From a logical point of view," he says, "all options are open
until there has been a loophole-free experiment."

And that openness could just possibly allow Einstein to have the last word.
Quantum theory famously predicts only the probabilities of experimental
outcomes, and most physicists believe that this reflects an ineradicable
randomness of the world at the smallest scales. It's an idea that Einstein
never liked. Of similar mind Nobel prize-winning physicist Gerard 't Hooft,
of the University of Utrecht in the Netherlands, is also convinced that
quantum theory itself must be an approximation of some deeper theory, one
that he believes should ultimately be deterministic, not random. If
Percival's suggestion is right and the detection loophole can never be
closed, it could be precisely because some deeper deterministic level of
physics makes sure of it, forbidding the existence of the quantum set-up
that would truly violate Bell's inequality.

't Hooft is trying to construct just such a deeper theory that would account
for all the strangeness of quantum theory, detection loophole and all. To
Gisin, Kwiat and many other experimenters, however, the detection loophole
seems like a minor detail - little more than a mopping-up operation that
future experiments will take care of. "I think it will be closed," Gisin
says, "quite possibly in my lifetime."

Percival is not so sure. "This issue can only be resolved by experiment.
That is why Bell experiments are so important."

How much faster than light?
Experiments certainly seem to have demonstrated that the influences of
entanglement move faster than the speed of light. But how much faster?

Gisin and colleagues undertook the first experiment to answer this question
five years ago. They sent pairs of entangled photons through fibre-optic
links between two Swiss villages 10 kilometres apart, and performed the
measurements in the two villages within about 5 picoseconds of each other.
The predictions of quantum theory still held up. Based on their set-up, the
team calculated that the entanglement influence must have travelled at least
10 million times faster than light.

Ah, but relative to what? In relativity theory, Gisin points out, a
faster-than-light velocity only makes sense if there is some special frame
of reference - something like the old "ether" through which light was
thought to propagate. Then all velocities have an absolute meaning in
relation to this frame. If this is the case, then experimenters will have to
think carefully about the implications before putting the influences of
entanglement to the test.

When they recorded a speed limit of 10 million times the speed of light,
Gisin and colleagues were measuring with respect to the local surroundings.
But it could be, of course, that the influence that lies behind entanglement
might have a fixed speed relative to some other frame of reference, such as
the faint microwave afterglow of the big bang, for example. Gisin and
colleagues also analysed this possibility, finding in this case a minimum
speed of at least 10,000 times the speed of light.


.

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