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Quantum Holography
Buzz Skyline writes "Physicists succeed where psychics fail. Researchers from Boston University propose a quantum holography system that can construct 3d images of objects sealed in closed containers. Could it lead to quantum luggage scanners at the airport?"
Here is a link to the
actual paper itself. It's a PDF file though
Yeah yeah, it's all funny but it ticks me off that nobody is pointing out that The principle illustrated in Schroedingers "cat" thought experiment are NOT THE SAME as the Heisenberg Uncertainty Principle. In fact, it ticks me off that nobody knows what the Uncertainty Principle is really about and people constantly confuse it with the whole indeterminate quantum particle state and whether does in fact create quantum indeterminacy on the macro scale (if a tree falls in the forest...) issue. Heisenberg's Uncertainty Principle establishes a mathematically defined absolute uncertainty balanced between the momentum and position of a quantum scale particle. The corresponding thought experiment would be the gamma ray microscope.
It Is the Nature of Information to Transgress Artificial Boundaries
*Anything* which firmly establishes the state of the cat will collapse the wave function. If you burn the box in a crematorium, the cat is definitely dead -- no uncertainty. If you "see" into the box using a method other than opening it, then you know the result. There are many ways to collapse the metaphorical wave function, observing it is just the most direct way, and also relates most directly to the position of an electron, which can best be determined by observation, though not with the naked eye.
Yes! That guy!
This is a good question, and there have already been several good answers. However, I don't feel like they've really answered your question.
Far from destroying the uncertainty principal, the article indicates that one of the "spooky" things about quantum holography is, essentially, the exploitation of the uncertainty principle.
Now, as to direct observation and the uncertainty principle: perhaps these should be explained for the casual /.'ers out there.
The uncertainty principle says that we cannot know exactly both the position and momentum at the same time. Momentum is a combination of mass and velocity. Mass often remains constant, so sometimes this is stated as "position and velocity" instead. Now, I used the word "exactly", and I meant just that. We can have a good idea of both numbers, but the more exact one measurement is, the less exact the other measurement will be. Basically, think of it this way: if we take a probe, like the tip of a pencil, and move it around till we find exactly were a particle is, we'll find it. But we'll also hit it and change its momentum.
Now, all observations require some kind of probe, be it pencils, electrons, or photons (light). A related feature of quantum mechanics is that the equations we use to determine where a particle (or wave, they're the same thing at this level) is going (the famous Schrodinger equations) don't actually tell us where a particle is going--only where its likely to go. So we don't even know how to say where it is going to go. In fact, it is considered that a particle does not have just one specific path until the particle has been measured.
In our case, that measurement--that is, the observation of the photons--occurs at the wall of the chamber. And from this data, convoluted equations work backwards to figure out what the photons bounced off of.
Hope that helps...
Holography basics (aimed at Highschool students level).
Books and information on Holography
Some more holography Theory>
--- Metamoderating abusive downgraders since my 300th post.
Abouraddy,A., Saleh,B., Sergienko,A., and Teich,M. Quantum holography (PDF, 169KB, 8pages), Optics Express, 9, 498-505 (2001).
Read the damn thing (if you can :-)), then discuss.
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