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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?"
true, but a few years ago, reasearchers transported a photon from point a to point b with out the photon traversing the space in between. this would let you get the photons into the container with out having to have a hole......of cource reading the results is a diffrent issue.
I am the Alpha and the Omega-3
http://www.sciam.com/explorations/061796exploratio ns.html
http://users.ox.ac.uk/~jsw/Schroedinger.html
The man who trades freedom for security does not deserve nor will he ever receive either. - Benjamin Franklin
it is not that the particles are ruining it, it is that quantom probability states that when you do not observe an object you can not make an asumption on its state. hitting it with particles will do nothing since we realy don't know if the particles are hitting it or not. what we are observing is the quantom entangles photons that have never been in the box and that is what give us the immage.....quantom entangle ment is the instant communication of 2 sub atomic particles. (this is what puts the GR folks on there head since 2 quantom entangeled particles could be 1,000,000 Lightyears away from each other, but they can communicate to each other instantly which would make that communication faster than light which is impossable according to GR.
I am the Alpha and the Omega-3
First, I'd like to point out that quantum computation and quantum encryption are two almost completely separate concepts. Quantum encryption is based on the fact that quantum states cannot be measured without altering. The most common example is the polarization of a photon, but it will work for any quantum state, so long as there exist, effectively, two unique states that can transmit the data.
Quantum computation, however, is much more complex and much more interesting. Quantum computers are based on the concept of quantum entanglement, the ability of a quantum state to exist in a superposition of all of its mutually exclusive states: It's a 1 and a 0. However, this is not as easy to use as one might think. While it's true that if you have n quantum logic gates you have the ability to input 2^n data values simultaneously (as opposed to only 1 piece of data if you have n digital logic gates), this is not going to be the end of classical computing for a few reasons. First, quantum computers have to be perfectly reversible. That means for every output there's an input and vice versa. And there has to be no way of knowing the initial states of the data. You don't process data, you process probabilities in a quantum computer; if you know exactly what any one value is throughout the computation, you can find out all of the values: the superposition ends and you're stuck with a useless chunk of machinery. This means YOU CAN ONLY GET ONE RESULT FROM ANY QUANTUM COMPUTATION, THE END RESULT. You can't see what the data in the middle is or the computer becomes useless. (Landauer's principle makes heat loss data loss. When your processor gets hot, it's losing data. If the same thing happened to a quantum computer, it wouldn't be quantum anymore.) Decoherence is what happens when you randomly lose data to the environment by design, not by choice, and the superposition ends. This is bad for Q.C. Oh, and quantum computers can only do *some* things faster, like prime factorization and discrete logarithms. Not multiplication or addition. Plus, the circuits that would do basic arithmetic would be bigger and slower than what you've currently got.
So what does this all mean? It means that quantum computers are going to provide some advantages (real quick big number factorization), and some disadvantages (that whole RSA standard). The most realistic initial use of quantum computers will be as add-ons to existing super-computers to resolve certain types of NP-Complete headaches that regular math can't simplify yet. At best they will someday be an add-on to your PC; but they will never replace the digital computer.~
If you want more info, check out ahttp://www.qubit.org, it's got some decent tutorials.
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...
I don't have a reference for you, but I can say that no, quantum entanglement does not allow FTL communication. To do anything interesting, you need to communicate information about the observation you made on one of the particles. Imagine twins -- one male, one female. They go to the two poles; at the North pole, somebody looks at one, and *boom*, she's female and the other one is male -- instantly. The people at the South pole look a microsecond later, and see that their twin is male. Okay... so? The people at the North pole haven't transmitted any information, even if the action occurred *instantly*.
The article doesn't make it clear, but the measurement taken in the chamber must, I have to assume, be transmitted and used in constructing that second image (it doesn't just *happen*; you can't shine a beam of light, even entangled photons, and expect them to magically scatter off nothing. When the first entangled beam is measured, quantities of the second half are determined, but that doesn't make them scattered, since it was *possible* they were in that state already... it has to be possible, that's how quantum physics works). It sounds like the information would be used in a second beam interfering with the intangled beam, but I'm not certain from the article... but I can guarantee that information has to be used.
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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No.
This concept was originally conceived sometime around 1930 by einstein, podolsky, and rosen as an argument intended to torpedo quantum mechanics.
basically they pointed out that quantum mechanics predicts that if you prepared a four state quantum mechanical system (ie 2 qubits) in a certain way (creating an EPR pair) they would exhibit "spooky action at a distance". at the time it was a fundamental principle that cause and effect had to obey the speed of light and therefore quantum mechanics was broken.
turns out there is massive amounts of evidance that cause and effect can be instantaneous over any distance and quantum mechanics goes on to be the most succesful scientific theory in history.
the scenario is this: alice and bob create an EPR pair, and then each takes one to opposite ends of the universe. when alice measures the state of her qubit, bob's qubit instantly becomes a known quantity.
it has been proven that to use this effect for communication requires the communication of classical bits of information (i believe it is the result of alice's measurement) which are governed by the speed of light. hence quantum entanglement can not be used as a truly instant messaging transport.
however, you can use this effect to achieve perfectly secure cryptographic key distribution and this has actually been done several times.
quantum computing is super cool and might actually be practical. check out http://www.qubit.org for some well chosen tutorial papers and links.
I like to explain it this way:
.wav file of a sine wave and edit it with your favourite sound editor. Zoom in so you see 100 cycles. Measure the time 100 cycles takes. From that you can calculate the frequency of your sine wave. At what time did this event occur? Well, the event is spread out over time. So we don't know the accuracy of the timing of the event very well.
Take a
Now zoom in more so only 1/2 a waveform shows. Measure it. calculate the frequency. You now have more accuracy in the timing of the event, but less accuracy of the frequency.
Heisenberg's principle is NOT the confusing thing about physics - it is plain reality! The thing that really is the source of the confusion is that the energy of a particle is related to its frequency - Just like the time and frequency were related in my example.
*IANAP*
--jeff
ipv6 is my vpn
It's more correct to say that if one entangled particle changes, the other changes too. But that only helps you do instantaneous communication if you can change an entangled particle in exactly the way you want. No one's figured out how to do that.
As far as we can tell at present, quantum nonlocality and "spooky action at a distace" exist, but cannot be made to transmit any information.
Looking at a paper I did about ten years ago, I found the following quote from Nick Herbert's Faster Than Light that summarizes the situation:
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