From: Walter Watts (wlwatts@cox.net)
Date: Tue Jul 09 2002 - 11:18:27 MDT
I STILL say not only does he play dice, but he's a compulsive gambler!!!
Walter
Enjoy......
----------------------------------------
God Doesn't Play Dice
Marcus Chown
NewScientist
6.29.2002
Core reality.
---------------
Just suppose the quantum world is built on more solid foundations. It
could explain a lot of weird stuff, says Marcus Chown
---------------
FOR a theory that has the world's finest physicists baffled, quantum
mechanics is fantastically successful. It has made possible computers,
lasers and nuclear reactors and explained how the Sun shines and why the
ground beneath our feet is solid. But it is also strange, frustrating
and incomprehensible. It insists that the microscopic world is a shadowy
realm where nothing is certain-where an electron can be in two places at
once and photons at opposite extremes of the Universe can communicate by
some kind of weird telepathy.
But some physicists are beginning to suspect that there's another level
of reality beneath the quantum world. Nobel prizewinner Gerard 't Hooft
believes that underpinning quantum weirdness is an old-fashioned
deterministic theory-one inwhich there's a simple relationship between
cause and effect. Antony Valentini of Imperial College in London has now
gone even further. He thinks that quantum mechanics may not always have
applied, and that in the early Universe matter danced to a different
tune. What's more, some non-quantum stuff may even have survived to this
day, tantalising us with the possibilityof eavesdropping on secure
cryptographic channels, constructing computers which outperform even the
fastest quantum computers and, most remarkable of all, sending signals
faster than the speed of light.
The reason for believing in a deeper level is that quantum theory merely
predicts the probable outcomes of measurements, not certainties. To
Valentini, it's abit like an actuary predicting the probability that a
man will die at a particular age. "This does not preclude a deeper level
of cause and effect, which could be used to predict precisely when a
given man dies," says Valentini. "It might depend on the detailed
condition of his heart and arteries."
Indeed, everywhere in physics where a theory predicts probabilities,
physicists believe there is a deeper level of certainty. Everywhere,
that is, except quantum physics. Why not there too? Most physicists
would say that this deeper level of explanation - a lower stratum or
"hidden variable theory" - is unnecessary because quantum mechanics
already fits all known experimental results. "They're saying quantum
theory works now -why look farther?" says Valentini.
Nevertheless, a few people have tried. One attempt is the "pilot-wave"
theory, proposed by French physicist Louis de Brogue in the 1920s and
developed by American physicist David Bohm during the early 1950s
Whereas in quantum mechanics the wave function is nothing more than a
mathematical convenience for calculating the probability that a particle
will be found at a particular point in space, in pilot-wave theory the
wave is real. It's an invisible but physical wave that guides particles
along, and has a current that drives the precise motion of the particle,
just as an ocean current drives a piece of flotsam. This theory
reproduces all the statistical predictions of quantum mechanics. "Most
physicists are quite sceptical about this interpretation-including
myself," says Lucien Hardy of the University of Oxford. "But it is
important because it establishes the possibility of giving quantum
theory a a so-called hidden-variable interpretation."
However, most physicists are put off this interpretation by a property
called non-locality- physical influences that travel faster than light.
Of course, even conventional quantum mechanics assumes non-local
effects. Between measurements, the spin of an electron can be loosely
thought of as in a state of high anxiety. flitting randomly from
spinning in one direction, dubbed "up", to spinning the opposite way,
dubbed "down". This has a remarkable consequence if two "entangled"
electrons have a total spin of zero between them - that is, the spin of
one is up and the other down. Nature forbids the total spin from ever
changing. So if the electrons are separated and a measurement on one
finds it spinning "up", the far-away electron must at the very same
instant plump for spinning "down". And vice versa.
"It doesn't matter if one electron is ma steel box buried under the sea
floor and the other is on the other side of the Galaxy," says Valentini.
"Each will respond instantaneously to the other's state, in total
violation of Einstein's cosmic speed limit, the velocity of light."
Yet while it's possible to think of non-locality as a quirk of quantum
mechanics - something that's peripheral to the meat of the theory-the
same can't be said for pilot-wave theory. Non- locality lies at its very
core. Take those two electrons again. Pilot- wave theory says that the
pair of particles we see moving about in three- dimensional space is
actually the projection of a single system that exists in
six-dimensional "configuration space". "The two particles are connected
because they are really a single, higher-dimensional system," says
Valentini.
Most physicists remain uneasy about non- locality because in our
everyday experience things do not seem to be inextricably linked. Any
theory that places this at its centre seems suspect. 't Hooft, of the
University of Utrecht in the Netherlands, is dead against the idea of
non- locality. Yet he thinks that a novel kind of hidden- variable
theory might offer a way around it.
His idea, formulated in the late 1990s, is that some kind of
deterministic theory can be applied at the very smallest scales of space
and time. If you could zoom in and observe events that last just 10 -43
seconds, in an area no more than 10 -35 metres across, you would find a
classically predictable theory with no need for probabilities and
uncertainty. 't Hooft describes it as being like a game of chess played
on a board with microscopic squares. Quantum mechanics is then a kind of
statistical theory that tallies all the smallest-scale events to give a
fuzzy average description of what's going on.
He has several reasons for believing quantum theory is built on deeper
foundations. One is our inability, despite 80 years of effort, to
reconcile gravity with the quantum world. Superstring theory makes many
claims, he says, but it's far too vague to be even remotely acceptable.
Another reason is more deep-seated. "lust like Albert Einstein, lam
unhappy about the fundamental statistical nature of the predictions of
quantum mechanics," he says.
't Hooft is still developing his ideas, but even if he's right, there'd
be no way of telling. By his reckoning we may never see the
deterministic layer underneath quantum mechanics, or even be able to
prove that it exists.
Which is why Valentini's latest ideas are so appealing. He thinks we
should find hard evidence that these solid foundations really exist.
Valentini believes that instead of rejecting non-locality, we should
embrace it. He points out that in conventional quantum mechanics, a
"suspicious coincidence" obscures non-locality. For example, you might
think that by using pairs of linked electrons like the pair described
above, you could create an instantaneous communication system that
defied the rule against anything travelling faster than light. But,
frustratingly, that's impossible, because you can never know before a
measurement which way an electron is spinning. So if one direction of
spin codes for a "1" and the other a "0" and you want to send a "1" you
can only be 50 per cent sure of sending a "1"- a level of uncertainty,
or noise that scrambles any message. "Although non- locality is a
fundamental feature of quantum theory, nature provides precisely the
amount of quantum noise necessary to make it unusable," says Valentini.
"Is that simply a coincidence? I don't think so."
He uses a thermal analogy. If the whole Universe was in a state of
thermal equilibrium - that is, characterised by a single temperature -
heat could not do any work. It couldn't move a piston, for example. "It
isn't that heat intrinsically can't do work," he says. "It's just that
temperature differences are needed to do work." In this imaginary state
of universal thermal equilibrium, random temperature fluctuations in any
machinery would be of precisely the right size to make any small random
temperature differences unusable.
Valentini suspects that quantum theory may merely describe a particular
state of the Universe in which quantum noise acts like these random
temperature fluctuations, making non-locality unusable and effectively
preventing messages being sent faster than light. According to
Valentini, in this special state we are unable to observe non-local
signals because they "cancel out" at the statistical level. This could
apply to any hidden-variable theory, but Valentini has done most of his
work on a type of pilot-wave theory.
His ideas are certainly controversial. "These conclusions depend on a
particular interpretation of pilot-wave theory which, whilst being
perfectly respectable, has the support of only a small number of
physicists," says Hardy.
But on the whole, physicists - including Hardy-do not dismiss it.
"Valentini is a serious physicist and a very deep thinker," says Hardy.
"I am a big fan of Antony Valentini," says Lee Smolin of the Perimeter
Institute forTheoretical Physics in Waterloo, Canada. "I think his ideas
are the most interesting and potentially true ideas concerning the
foundations of quantum theory that I have heard for some time."
If Valentini is right, the implications are profound. lust after the big
bang, the Universe may have existed in a state in which non-locality was
not cloaked by random noise, he says. Interactions between particles in
this early Universe then rapidly caused it to relax into the special
"equilibrium state" we find today. These interactions, Valentini
suggests, imply that the pilot-wave currents driving particles along
were so convoluted that they scrambled the particles' probability
distributions. This can be likened to interactions between hot gas
particles - which on average transfer energy from fast-moving to
slow-moving particles - causing the gas to relax into a state of thermal
equilibrium.
In our world, the probable location of a particle is related to the
square of the amplitude of its wave function. But in this early
Universe, before quantum noise set in, probability distributions might
have been more sharply defined than the square of the wave function.
With less quantum noise to blur things, it would have been possible to
locate particles with greater certainty. And since non-locality wasn't
blurred out, this means that at this time, signals could travel faster
than light. For example, there would be less uncertainty about the spin
state of an entangled pair of electrons, so a message could be encoded
in electrons on one side of the Universe and sent to the other
instantaneously.
Valentini has reason to believe this was the case. According to him, a
split second after the Universe's birth there were two competing
processes going on. One was the interaction between particles -
analogous to the interaction between molecules in a gas - which drove
the Universe towards a noisy equilibrium. But this approach to
equilibrium was countered by the tremendous expansion of the Universe
which was pulling matter apart. Only when the expansion had slowed could
particle interactions dominate, says Valentini, allowing matter to slip
into the blurry, uncertain form we see today. This point was probably
reached when the Universe was about 10 -43 seconds old, he suggests.
With the transition occurring so quickly, you might think there could be
no significant consequences. Not so, says Valentini. This transition
could solve the puzzle of why far-flung parts of the Universe are at the
same temperature and have the same matter density. How could they have
influenced each other if there wasn't even time for light to have
travelled from one to the other? The standard solution to this conundrum
is inflation, a hypothetical super-fast expansion of the Universe
inwhich it arose from a volume so small that very early on all parts
knew about each other. But if there was no speed limit, there is no
puzzle.
There would be consequences for inflation too, if it really occurred.
Quantum fluctuations in the fields that physicists believe drove
inflation should be imprinted on the cosmic microwave background as
small variations in temperature. "Those variations may therefore reflect
quantum fluctuations in the early Universe," says Valentini. "If the
actual fluctuations don't obey the rules of quantum mechanics, we ought
to be able to see the fossil imprint in the microwave background today."
Data from NASA's satellite observatory MAP could provide the answer next
year, he says.
What makes Valentini's theory even more surprising is that some
non-quantum matter might have survived to the present day. Since the key
to the transition to the equilibrium state is the interaction between
particles, any particles that ceased to interact around the cut-off
point about 10 -43 seconds after the big bang could get left behind. In
particular, Valentini suggests that some gravitons - the hypothetical
carriers of the gravitational force - could have become isolated at
about the time of the transition. In other words, gravitons left over
from this time might still be in a non-quantum state today.
According to Valentini, there may be hitherto unknown non-quantum
particles too. "It's conceivable they may even make up the invisible
dark matter which dominates the Universe," he says. "Matter following
familiar quantum theory could be a minor component of the Universe."
Particles of non-quantum matterwould look like normal particles, they'd
simply not obey the statistics of familiar particles. The location of a
particle trapped in a box, for example, would not be dependent on the
square of its wave function: its position could be pinned down more
precisely.
How could we test such an outlandish idea? Identifying gravitons that
survive from the instant after the big bang seems unlikely, and even
getting hold of dark matter might be difficult, to say the least. But it
is conceivable that dark matter particles could decay into photons that
preserve the non-quantum behaviour of their parents. If you could detect
such photons- by pointing a telescope at a small region of dark
matter-they would behave differently from quantum photons. Pass ordinary
photons through a pair of slits, for example, and they produce distinct
dark and light bands of interference. The bands produced by non-quantum
photons, on the other hand, would be blurred.
There's even some possibility that non-quantum matter is being created
in today's Universe. Valentini's guess is that gravity could shift
matter that obeys quantum theory back to its primordial non-
equilibrium state. This would probably take the ferocious gravity of a
singularity in a black hole, though.
If we could somehow get hold of non- quantum matter, it would be magical
stuff. For one thing we could violate Heisenberg's uncertainty
principle, which puts a limit on how accurately we can measure things
such as the location of a particle. To locate a particle, it has to
interact with something else, for example when a photon bounces off it
in a detector. The problem is that there is an uncertainty even in the
position of the photon. "However, if we had photons obeying a
probability distribution sharper than that of standard photons, we could
locate things with greater certainty," says Valentini.
This also means we could use the stuff to eavesdrop on secure
cryptographic channels, says Valentini. Quantum cryptography is 100 per
cent secure because any attempt at eavesdropping would be noticed. The
simple act of reading the secret key transmitted as a string of quantum
1s and 0s introduces disturbances
(New Scientist, 2 October1999, p 28). But if eavesdroppers possess
non-quantum matter, they could beat the uncertainty principle and
distinguish the state of the bits without disturbing them. This is
because non-quantum particles contain less noise. Just a very weak
interaction between them and the quantum bits - an interaction too weak
to disturb the bits - is enough to leave a discernable signature in the
non-quantum particles that could be used to decrypt the message.
And there's more. Non-quantum matter would enable us to build a
computer which massively outperforms "conventional" quantum computers.
These hypothetical machines would exploit the fact that a particle such
as an atom can be in many states at once - a so-called superposition-to
do large numbers of calculations simultaneously (New Scientist, 8 June,
p 24). The problem is that you need a carefully crafted quantum program
that concentrates the answer in a single branch of the superposition,
from where it can be read.
So far such algorithms have been found for only a few specialised
problems. But using non- quantum matter you could in theory access all
the myriad parallel calculations of a quantum computer. It could be used
to observe the computer's quantum state without collapsing the wave
function, enabling us to read the results of all the parallel
computations.
But far more remarkable than all this would be faster-than-light
communication. You could exploit non-locality without quantum noise
getting in the way, using it to control robotic probes on planets at the
other end of the Solar System in realtime, for example. Troublesome time
lags while instructions "crawl" at the speed of light across space would
become a thing of the past. Why send humans on long, dangerous missions
to Mars when robots, controlled from a comfortable lab on Earth, could
do the job perfectly well?
And this sort of communication would force us to revise relativity
theory, says Valentini. Contrary to what is suggested by Einstein's
theory, there would have to be an underlying preferred time - a sort of
Universe-wide GMT.
Valentini will have a hard time convincing sceptics. But it could be
worth it. "It would mean that physics was finally making progress, on a
problem on which we have been stuck for many decades," says Smolin.
"Right now we're staring into a sort of quantum fog," says Valentini.
"If we admit that an unexplored level might lie behind it, a whole new
world comes into focus."@ Further reading: The Quantum Theory of Motion
by Peter Holland (Cambridge University Press, 1993) "Subquantum
information and computation" by Antonyvalentini (www.arxiv.orglabslquant
"Hidden variables, statistical mechanics and the early universe"
byAntonyValentini
(www.arxiv.orglabslquant-ph10104067) "Signal-locality and subquantum
information in deterministic hidden-variable theories" by
AnlonyValentini
(www.arxiv.orglabslquant-phl0112151) "How does God play dice?
Pre-determinism at the Planck scale" by Gerard 'I Hooft
(www.arxiv.orglabslhep-th10104219)
341 NewScientist I29lune 2002 www. newscientist. cam
-- Walter Watts Tulsa Network Solutions, Inc. "No one gets to see the Wizard! Not nobody! Not no how!"
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