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ISIS Press Release 16/03/04

Announcing special series

Quantum World Coming
*******************

A more technical version
(http://www.i-sis.org.uk/full/quantumworldcomingFull.php)
of this article
complete with illustrations and references is posted on ISIS
members’ website. Full details here
(http://www.i-sis.org.uk/membership.php).

Until fairly recently, the conventional view held by most
physicists is that nature is somewhat sharply divided into
the classical domain of every day objects in which Newton’s
laws of mechanics hold, and the weird and wonderful world of
quantum systems at the scale of elementary particles, atoms
and simple molecules, in which ‘things’ are both wave and
particle, and can be in two places or multiple,
contradictory states at the same time. Quantum systems are
destroyed by the act of measurement, which brings them
abruptly into the ordinary classical world. Austrian
physicist Erwin Schrödinger, who, like Albert Einstein,
never really believed in quantum theory, invented the story
of a cat, now named after him, to illustrate how absurd the
situation is. Schrödinger’s cat is locked in a box
containing a capsule of deadly cyanide gas that would be
released the moment that a radioactive nuclide undergoes
radioactive decay. The way to find out if the cat is dead or
alive is to open the lid of the box, which is equivalent to
performing a ‘measurement’ and bringing the ‘quantum system’
of the cat in the box abruptly into the classical world.
Schrödinger’s cat asleep by Mae-Wan Ho But before someone -
a conscious being - opens the lid, the cat in the box is
neither dead nor alive, but both. It is said to be in a
superposition of two alternative states: being dead and
being alive, or more accurately, all possible combinations
of being both dead and alive at the same time. Someone
opening the lid instantaneously ‘collapses’ the quantum
superposition (or the wave-function describing this state)
and only a classical result can be observed. But can’t the
cat surely collapse its own wave function by experiencing
itself either dead or alive? Over the past 20 years, the
scale at which quantum effects can be observed has become
increasingly large, so the problem of Schrödinger’s cat is
all the more relevant to our picture of physical reality.
Could there be some conceptual error involved in the idea of
measurement and the collapse of the wave function itself?
Many surprising discoveries are raising questions over the
standard interpretation of quantum theory, and that is
perhaps the most exciting development in contemporary
western science in the 21st century. The mere promise of
quantum computing is enough to send people into a frenzy of
speculation on the coming quantum information revolution
that will make current information technology look Stone
Age. Quantum computing not only provides an exponential
increase in computing power, but can also solve problems
that the classical computer can’t handle. However, there
appears to be insurmountable engineering hurdles in actually
building a quantum computer. There may well be deeper
problems involved with the whole idea of a quantum computer
that we can actually control and use. A bit closer to
realisation is quantum communication based on entirely new
interactions between light and matter in quantum optics, and
quantum cryptography to keep military and commercial secrets
snoop-proof; potentially a boon for dictators, corporations
and terrorists alike, but what’s in it for ordinary people?
The way I see it, the quantum age entails a shift to a truly
organic way of living and perceiving the world that will
reconnect western science to the deeply ecological and
holistic knowledge systems of all indigenous cultures, most
of which are facing extinction. It will make us realise how
urgently we need to protect and revitalize them as the real
"common heritage" of the human species. A quantum world is a
radically interconnected, interdependent world where every
entity evolves like an organism, entangled with all that
there is. ISIS will be circulating a unique series of
articles that will change your life. So look out!

Quantum World Coming

Nature is Quantum, Really
********************

Matter, even big clumps of it, is simultaneously wave and
particle. Dr. Mae-Wan Ho (m.w.ho@...) explains

Which slit did the buckyball go through?

One of the first experiments to show up the strangeness of
the quantum world consisted of shining a light through two
narrow slits onto a photographic plate placed some distance
behind the slits (Fig. 1).

Figure 1. The two-slit experiment

When only one slit is opened, an image of the slit is
recorded on the photographic plate, which, when viewed under
the microscope, would reveal tiny discrete spots. And this
is consistent with the interpretation that individual
particle-like photons, on passing through the slit, have
landed on the photographic plate, where each photon causes a
single silver grain to be deposited. When both slits are
opened, an interference pattern of alternating bright and
dark zones forms on the photographic plate, which is
consistent with a wave-like behaviour of the light: the two
wave trains, on passing through the slits, arrive at
different parts of the photographic plate either in phase,
where they reinforce each other to give a bright zone, or
out of phase, where they cancel out to give a dark zone. On
examining the plate under the microscope, however, the same
graininess appears, as though the light waves become
individual particles as soon as they strike the plate.
Numerous other more sophisticated experimental
configurations have been devised to investigate this
phenomenon, and always the conundrum remains. Photons are
split into superposed reflected and transmitted states, or
into opposite polarized states, that are capable of
interfering when brought together again; but as soon as
information is gained as to which path the photon has taken,
or which polarised state it has adopted, then it behaves as
an ordinary particle. More remarkably, the two- slit
experiment has been repeated with increasingly massive
particles and essentially the same results have been
obtained: electrons, neutrons 1800 times as massive as the
electron, and more recently ‘ buckyballs’, a newly
identified form of carbon molecule consisting of 60 atoms of
carbon arranged in the shape of a football, and possibly,
even a small protein. Professor Anton Zeilinger, who leads a
group in the University of Vienna engaged in these
experiments, said when giving the 16th Schrödinger Lecture
in London last November that they are planning to try a
small virus next, and is quite confident that it too, will
behave as both wave and particle. There is quite a gap
between virus and a mouse, or a human being, but who is to
say we are not both a wave spread out in space and a
seemingly solid body that can bump into furniture?

Macroscopic quantum objects?

Schrödinger would have been astonished by all these findings
if he were alive today. After all, he invented the parable
of the cat named after him to show what absurd things
quantum theory would have us think about: that an entity
could be simultaneously in mutually contradictory states
until the instant it is ‘measured’. But what constitutes a
measurement? Quantum physicists John Bell, who died a few
years ago, had apparently called for the word ‘measurement’
to be banished from quantum theory. At a workshop in 1990
concerned with how quantum effects can manifest on a
macroscopic scale, the concept of measurement became very
ambiguous. Philip Ball, reporting in Nature, said, "the most
profound message from that meeting was that interpretations
of quantum theory are no longer a matter of philosophical
taste." Why? It was because of the development of electronic
systems of remarkable sensitivity, and many ‘thought
experiments’ could be directly tested. It had become
possible by then to create individual macroscopic quantum
objects, perhaps a few centimetres in size. Among the first
most promising candidates for displaying macroscopic quantum
behaviour were various kinds of electronic circuits,
particularly semiconductor structures, in which electrons
behave like a two-dimensional gas, and super-conducting
rings (which conduct electricity with zero resistance)
containing weak links in the SQUID (Super Quantum
Interference Device) magnetometer. SQUID magnetometers are
increasingly used to measure the ultraweak magnetic fields
coming from the body as electric currents flow through it.
At the 1990 workshop, Terry Clark of University of Sussex in
Britain discussed the then state of the art in SQUID ring
experiments. The weak link in these rings – typically made
from a low-temperature superconductor such as niobium - is a
point contact, and transport of correlated electron pairs
(called Cooper pairs) across the contact relies on quantum
tunnelling through the energy barrier created by the weak
link. This is a probabilistic process resulting in a build-
up of charge on either side of the junction, so the device
develops a capacitance (charge storage). At the microscopic
level, charge Q and magnetic flux f are related, like
position and momentum by the uncertainty principle that’s
fundamental in quantum physics, DfDQ > h/2. That means if
you measure one quantity precisely, the other is totally
uncertain: if you know the exact position of a particle, its
momentum (mass x velocity) could be anything from zero to
infinity, and conversely, if you pinpoint the momentum, then
the particle could be anywhere in the universe. The weak-
link ring can adopt two quantum modes – a flux mode, in
which charge flows and could be anywhere in the system, but
the magnetic flux lines through the ring tend to be
localized inside the ring; and a charge (capacitive) mode,
in which charge tends to be localized, but not the magnetic
flux. Different quantized (discrete) energy states
(eigenstates) of the charge and flux modes are coupled by
some characteristic tunnelling frequency so that in
principle, the ring may lie in a quantum superposition of
the two states. Is it possible to catch the ring in such a
superposition? This is where measurement comes in. According
to the standard ‘Copenhagen’ interpretation, the act of
measurement ‘collapses’ the quantum superposition. But the
hope is that if the coupling (connection) to a measurement
device is very weak, this collapse would not happen. Terry
Clark’s team managed to set up just such a weak measurement
system and obtained results suggesting that the SQUID ring
could exist in a quantum superposition of both the flux mode
and the charge mode (see Box). So, where does the quantum
world stop and the classical start? One might say I am a
quantum being between the acts of living and dying, like
Schrödinger’s cat. Read on.


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