Posted on 06/23/2002 9:44:18 PM PDT by gcruse
The weirdness barrier
What keeps us safe from the absurdity of the quantum world?
YOU could be in two places at once, according to quantum mechanics. But although it 's theoretically possible, the apparent absurdity of extending this feature of the atomic world up to everyday scales has puzzled physicists for decades, since things like this just don 't happen to large objects such as cats and people. Now researchers have devised an experiment that could finally explain why.
Tiny particles such as photons or atoms can readily be put into a quantum superposition -existing in two different states or places at once. Yet it doesn 't seem to happen to big things. Many scientists think that 's because interactions with the environment disturb the delicate superposition and force the object into either one state or the other.
But others, such as Keith Schwab at the Laboratory for Physical Sciences in College Park, Maryland, think there may be more to it. There could be as yet undiscovered mechanisms that force objects to choose a single state, so quantum mechanics as we know it might just be an approximation that fails for larger objects.
The biggest objects ever shown to be in a superposition are molecules. In 1999, Anton Zeilinger at the University of Vienna showed that a buckyball -a spherical cage built of 60 carbon atoms -could travel through two parallel slits at the same time ( New Scientist, 16 October 1999, p 27) . This only works if the whole experiment is chilled and kept well isolated from the environment. Contact with the outside world, through molecules in the atmosphere or even light, collapses the superposition of the buckyball so it only travels through one slit. Given better isolation, could you keep large objects like cats in a superposition indefinitely?
Physicist Roger Penrose, based at Oxford University, has proposed an experiment that would find out ( New Scientist, 9 March 2002, p 26) , but it would probably have to be space-based, so is unlikely to happen any time soon.
But Schwab hopes to resolve the issue quickly. With Andrew Armour, now at the University of Nottingham, and Miles Blencowe at Dartmouth College in Hanover, New Hampshire, he has built a silicon beam whose length is just a fortieth of the width of a hair. This is small by our standards, but vast compared with a buckyball. Next to the beam is a strip of aluminium called a Cooper pair box attached by insulating contacts to an aluminium loop (see Graphic).
Electrons in the aluminium loop can jump across the insulation and into the Cooper pair box. Because this "tunnelling" effect is quantum mechanical, these electrons can be in the Cooper pair box and the aluminium loop at the same time, giving the box two different charges at once.
The silicon beam is positively charged, so it will bend towards the box if this has extra electrons. But when the box is in two charge states simultaneously, it should force the beam to be in two places at once.
Using a detector called a single electron transistor, the researchers will measure the position of the beam to find out how long it lives a split existence. If it collapses into a single state faster than interactions with the environment would force it to, there must something else going on. What 's more, the exact timing could tell scientists just what is putting a stop to the quantum weirdness.
The test is due to go ahead within 18 months. According to Will Marshall at Oxford University 's Centre for Quantum Computation, "Tests like this will show us why a football doesn 't go in two different ways when we kick it."
<|:)~
Take the same aspirin twice,
then call me in the moring.
Okay, so is the fundamental big deal here just that this beam is the largest entity which will have been observed to be in a superposition of states?
Or is it that the observational apparatus (the beam) would be observed, in turn, by the single electron transistor, to be in a superposition of states?
If you equate this to the original postulation of quantum using the 'cat in the box' model, it makes it easier to visualize: Start with your body and mind at complete rest - no motion, no nothing for mental stimuli. Then let's say you decide to move your head. In our observed reality, you move your head. However, the path in your quantum state had a fork in it - in another quantum reality you didn't move your head. The 'other you' that moved on from that point in linear time exists - only you can't observe that path. These forks in the direction of all of our lives started at the moment of birth, and have continued ever since. Where could your life have gone with different decisions? Hard to imagine.
"Our name is Legion. And we are many."
LOL!
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It's the beam, which is maybe twenty orders of magnitude larger than an electron. Like your headlights being on high beam and low beam simultaneously. No, forget I said that. +=<)B^)
Is the word "reality" accurate here? Seems to me it exists only in theory.
That may explain the "nine lives" thing.
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