Posted on 09/14/2006 8:19:40 PM PDT by annie laurie
Heisenberg's uncertainty principle limits what we can know about the quantum world. Now the uncertainty principle is being harnessed to see if it is possible to identify a point at which matter begins to exhibit weird quantum behaviour.
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Schwab's team fabricated a nanoscale resonator - the equivalent of a tiny pendulum - on a silicon chip, which oscillates at 20 megahertz. On the same chip, they created a single-electron transistor and electrically coupled it to the resonator in such a way that any change in the resonator's position caused a change in the transistor's current.
Measuring the current should cause back action in the resonator - and it did (Nature, vol 443, p 193). In most cases, the back action caused the resonator to get noisier or "hotter" than it would have if the measurement hadn't taken place. But when the team set the transistor voltage to a value that let electrons tunnel through the device, allowing the transistor to absorb energy, they found that the resonator cooled from the ambient temperature of about 500 millikelvin down to about 300 millikelvin.
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(Excerpt) Read more at newscientist.com ...
ping
bookmark. Interesting article.
OH, and another thing: ping!
Quantum duck alert.....quark, quark, quark.
cool !
It's like the old superstition - "Naming calls".
I thought Schrodinger proved it starts at the cat-level.
Charm is for quarks (shamelessly stolen from Connie Willis)
Elucidate. It in your post is the object of what?
bump
I guess in this case, it's a cool cat.
These sorts of experiments certainly demonstrate a technical virtuosity, but I resist the idea that they are necessary to illuminate "quantum weirdness", which is readily evident in the world as we experience it, minute to minute.
In fact, it is Quantum Uncertainty which "holds up the world". It is the only thing which prevents atomic electrons from collapsing into the nucleus.
Note that an electron confined within a radius r of a proton will have energy -e^2/r, so it can continually lose energy by falling inward, but by the Uncertainty Principle, it must have a residual velocity such that r (mv) > h, so mv > h/r, and this implies a kinetic energy mv^2/2 > h^2/(2mr^2), so if r gets too small, the "confinement energy" will overwhelm the (negative) Coulomb energy.
To estimate a balance point, equate the magnitude of the opposing effects and get e^2/r = h^2/(2mr^2) or r = h^2/(2me^2), an approximation of the Bohr radius of the Hydrogen atom.
"Please observe, gentleman, how facts which at first seem improbable will, even on scant explanation, drop the cloak which has hidden them and stand forth in naked and simple beauty." - Salviati
bump
Very cool! Thanks.
Thanks for this ping. I definitely would have missed the article.
Well, that kinda seems like peeking in the cat's box. We can't do that.
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