Fwd: Nature is Quantum, Really

16 Mar 2004 15:07:13 -0000

Nature is Quantum, Really

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press-release ISIS Director m.w.ho

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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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http://www.i-sis.org.uk/quantumworldcoming.php

 

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