Posted on 12/20/2001 5:17:16 AM PST by Father Wu
Teleportation is a name given by science fiction writers to a procedure in which an object disappears in one place and reappears in another instantaneously (this is classic teleportation; some authors explore the possibility that the original object doesn't disappear, resulting in there being two sets of the same thing). A good analogy of how a teleporter works is that it works like a 3-D fax machine.
For a long time scientists thought that teleportation was impossible because it violated one of the basic laws of quantum mechanics (Quantum mechanics is a discipline that describes the structure of the atom and how the particles in and around an atom move and react with each other. It also explains how atoms absorb and give off electromagnetic energy. It explains that when an atom releases light energy it doesn't release it in a steady flow. Instead it releases it in bundles of energy called quanta.), called the Heisenburg Uncertainty Principle (I'll talk about this later), which says that you can never exactly copy something. Then, in 1998, an international group, made up of six scientists and centered at the University of Innsbruck, proved that classical teleportation was possible, but at the moment only possible for photons and electrons. We won't be able to teleport ourselves in the near future, but it is not impossible that one day we might be able to.
Werner Heisenburg was a great German physicist who is best remembered for his contributions to quantum theory. He was born on December 5, 1901 in Wuzburg, Germany. He studied under Arnold Sommerfeld and earned his doctorate in 1923. For three after this he worked with Niels Bohr in Copenhagen. During most of this time he was working on the problem of how to describe the path of an electron using a matrix, which is a set of numbers use to plot the path of something. He was awarded the Nobel Physics Prize for his work in 1932.
He discovered the Uncertainty Principle in 1927, one of his most important pieces of work. The U.P. (Uncertainty Principle), summarized, states that one cannot know the exact position of something and its velocity (all this would tell you exactly where the object would be any given time) at the same time. You can find out one or the other, but you can never know both. This rule holds true for the most accurate measurements that we can take. The principle works because with each measurement that you take you disrupt the particle's path and the path of the particle that you used to measure the object. So, you can never accurately get both the position and velocity of an object due to the disruption caused by the measurement.
Another part of the U.P. states that the more accurately an object is scanned the more it is disrupted (this relates to the first part of the theory). This eventually causes the object to become completely disrupted before the scan is complete.
This has always been a stumbling block for scientists who are trying to find a solution to teleportation, because to teleport an object you first have to completely scan the object before teleporting it; but the Innsbruck team found a way of getting around this by using another aspect of quantum theory called the Einstein-Poldosky-Rosen Effect, or entanglement. Albert Einstein, Boris Podolsky, and Nathan Rosen discussed this effect in a paper. When two particles are entangled (say a pair of photons), the share the same properties at all times. If you entangled a pair of die, the dice would always turn up on the same number, no matter how far away they were from each other. And the number would still be completely random. Einstein called entanglement a "spooky action at a distance".
For many years it was thought that entanglement had no use, other than to prove the quantum theory, because quantum mechanics was the only field that could explain the bizarre behavior.
The Innsbruck team used the EPR Effect to bypass HUP by entangling the object to be teleported. That way all the unscanned information in the object would be passed to the teleported object through EPR.
The form of quantum teleportation that the scientists at Innsbruck came up with works like this. Alice wants to teleport an object A to her friend Bob. To do this she firsts entangles objects B and C. The n she sends object C to Bob. Once she knows Bob has object C she scans objects A and B together. This disrupts both of them and causes B's state to become equal to A's state (this part is difficult to comprehend). Now since A=B and B=C, A=C. Once this is done the scanned information is sent to Bob by conventional means (radio, ex.) and Bob processes object A, formerly object C, accordingly. In the scanning process the original object A is destroyed, ending in only one copy of object A, a classical teleportation.
This differs from a classical fax in that the original copy is destroyed in the process. Another major difference between the two is that teleportation takes three objects instead of just two.
The first action in the teleportation experiments done by the Innsbruck group is to create two entangled particles. This is done by sending a pulse of ultraviolet light through a type of crystal called a calcite crystal. This type of crystal is called a "non-linear crystal", probably because it splits photons (I wasn't able to find the definition). Inside of the crystal the UV photon is split into two photons whose polarization is entangled (polarization is the electrical charge of the photon. The polarization constantly changes). These first two photons are photons (objects) B and C. After the photons exit the crystal the UV pulse is reflected back through the crystal, while B and C are reflected to different stations. Photon C goes on to the receiving station where the teleported object will end up. Photon B is directed to the sending station. The pair of entangled photons are detected and the experiment starts. When the UV pulse is reflected back through the crystal photon A is created. A is sent to the sending station where a Bell-State measurement is performed on it and on photon B at the same time. A Bell-State measurement is the type of measurement the changes the state of C into the state of A. During the measurement A is scanned and the information is sent to the receiving station. There is a 25% chance that photon C will turn out exactly like A. So if the polarization is determined to be not the same polarization as A was it is sent through a crystal that will rotate its polarization until it matches A's (A's polarization could have been up, down, right, or left). The process has not been perfected yet and has a success rate of 75%.
The future of quantum computing is a promising one. Unfortunately, we won't be able to teleport humans in the foreseeable future. This is for a variety of reasons, all of them engineering. One of the problems is that the object to be teleported has to be completely isolated. That would be hard to do with a living organism. Another problem would be entangling the objects, although it could be done with large objects. Entanglement has already been demonstrated with Buckyballs, molecules made up of 60 atoms of carbon.
One of the most promising aspects of quantum teleportation would be in the field of quantum computing. Quantum computing is an experimental field of computing that uses atoms and molecules as bits. It is ultra-fast, about 1x10^9 times faster than today's super computers (the most powerful computer in the world could download the entire Internet in 2 seconds). This means that it would take a quantum computer 1 year for something that would take a conventional computer 1,000,000,000 years. Quantum computers have another advantage over conventional machines. Conventional computers will eventually hit physical limits or the facilities used to manufacture them will become too expensive to build.
Nobody thought much about the theory of quantum computing until 1994. A scientist named Peter Shor at AT&T discovered that how you could factor the prime factors of a number using a quantum computer much faster than with a conventional computer. The discovery fascinated scientists and horrified the security industry. It started off a wave of research in the field.
The great speed of quantum computers comes from the way they use atoms for qubits, or quantum bits. Unlike conventional computers a single qubit can represent more than one conventional bit. This is called superposition, or one thing representing more objects or ideas than just it. Qubits can do this because the atom or molecule that it is made up of can be made up of usually have more than one characteristic (ex. Electrical charge, spin axis, etc.) that fluctuate. Scientists control and measure the effects of these characteristics. They then are able to transform them into an extremely powerful computer.
In 1996 Neil Gershenfeld set out to build a quantum computer with a group at the University of California. Their first problem was to find a material that could be completely isolated and could have information entered, calculated, and measured with out decoherence occurring (decoherence occurs when an object or substance that is totally isolated interacts with outside forces or objects. This would cause calculation to become impossible in a quantum computer. It's like you were reading a book and then somebody started changing the script, ripping out some pages, added in new ones, and scribbled over other pages). The group then realized that liquids would be perfect, instead of isolating a single atom or molecule (this is for a very low powered quantum computer). Since all the molecules or atoms in the liquid would be the exact same, it wouldn't matter if the molecules interacted during the computations.
An atom's nucleus is constantly spinning like a gyroscope. The direction of the spin of the nucleus of an atom depends on the outside magnetic forces that are influencing it (like a magnet). The spin can either be parallel with the magnetic field (this would be like a gyroscope spinning on top of your finger, right side up) or anti-parallel (this is like a gyroscope spinning on your finger upside down). Now, when you apply an outside magnetic field, the spin axis of the nucleus will spin (like a gyroscope starting to wobble on your finger). If you turn a magnetic field on and off very fast it will cause the spin axis to completely rotate (you could rotate the spin axis 90 degrees or 180 degrees; it just depends on how long and how fast you turn the magnet off and on). Then, when you turn the magnet off the spins go out of alignment, until the magnet is turned on again. When the spins go out of alignment the atoms lose energy, which they emit in the form of radio waves. So if you rotated a spin 90 degrees it would give off a different amount of energy than if it had been rotated 180 degrees. The radio signals are picked up and translated by the same device that sent out the magnetic field. This process of manipulating and reading the energy emitted from the atoms is called NMR or Nuclear Magnetic Resonance. It works exactly like a MRI does. Different frequencies of NMR affect atoms of different elements in different ways. Like a hydrogen atom might remain the same while a carbon atom is rotated.
In QC (quantum computing) the spin of an atom (parallel, 90 degrees, anti-parallel, and anti-parallel 90 degrees) stands for a qubit. Parallel equals 0,0, ninety degrees equals 0,1, anti-parallel equals 1,1, and anti-parallel 90 degrees equals 1,0. Scientists measure the energy levels emitted by the atoms and are able to tell what qubit an atom represents.
Another thing the spins of an atom are affected by is the spin of its neighboring atom. In molecules atoms of different atoms are often side by side. In the molecule of chlorophyll (CHCl3) the spin of the carbon atom is dictated by the spin of the hydrogen atom next to it. This could have been a liability to deal with while designing a qc (quantum computer) but instead it forms the basic unit of computing, called the logic gate. In a computer a logic gate data is processed. Microchips are made up of logic gates. The interactions of the carbon and hydrogen atom forms a type of logic gate, the exclusive-OR logic gate. This is sometimes called the controlled-NOT gate. A NOT logic gate is the simplest type of logic gate. All it does is inverts the input. On a controlled-NOT gate the output depends on the state of the inverter (the output will be different depending on the spin of the hydrogen atom). Once the spin of the carbon atom has been inverted it sends out a radio signal which the operator of translates into the output.
Using an array of these devices that are all coordinated together it would be possible to create a super supercomputer, billion times faster than today's super computers.
Quantum teleportation might eventually be used for transferring information between logic gates. It will be a while before we will be able to build a quantum computer that is fast enough to compete with today's fastest computers, but it will definitely be worth the wait. One huge advantage to qc is that they are much easier and cheaper to manufacture than conventional computers.
Firstly, “object's potential energy” is a rare but true example of imprecision of speech that penetrated physics. We must keep in mind that the object does not have any potential energy: it is the system comprised of the Earth and the object that has U=mgh. Point taken. However, in an earth/object system, one either has to accept that energy is transferred from one to the other via the potential field, or that each object retains only its own energy and does not beam it around. I lean towards each object retaining its own energy. While I agree that the final net energy change of the system is 0, I think the object's energy was always inherent in the object itself and not "borrowed" from the Earth.
Now you appear to step into the General Relativity, where no one would use U=mgh (it is an approximation even in classical mechanics applicable to small distances only. Can you recommend appropriate reading material to help enlighten me?
The object’s mass is merely a proportionality constant in the expression for kinetic energy T = m (v^2 /2). The factor m in the expression U = m g h is not even the same mass. None of them hover, has anything to do with the dimensionality of the space-time. Here is where we start to diverge. I am aware that m is a proportionality constant as stated above, however, I disagree with the statement " None of them hover, has anything to do with the dimensionality of the space-time." It matters deeply (IMHO) because their (apparent) energy state is in part defined by the space-time around them. I am viewing mass as a dimension in and of itself that interacts with the other 4.
I am sorry to disagree but the expression dt is a time increment If anything, limits (of which the derivative dx/dt is one) involve variables, not constants. yes, it IS an increment, but it is a CONSTANT increment. My point related to the idea that dt = 1 second (for example) is not a constant, but varies. For example, if I am correct, my calculations indicate that rate of time at sea level is different than rate of time in orbit. If I took two perfect clocks, kept one on the ground, launched the other into orbit, they would become dis-synchronous. More specifically, the clock in orbit would read one second more time after ~84 years at an altitude of 175 miles. The problem I have with the dt is I do not believe it IS a constant increment. I had a fascinating article (unfortunately, my father-in-law pitched it) that discussed a aprticular phenomenon, wherein the author (can't remember his name, he was Chair of Physics at MIT in the late 50's) was describing how his system of equations for the phenomenon under discussion accurately predicted all conditions of it, where competing systems of equations only worked in certain subset conditions. The part I found interesting was that none of his equations had time in the denominator (or if he did, they cancelled out somewhere) while all of the competing systems did have a non-reduceable time in the denominator (I really need to find that damn article).
The constancy of the speed of light is an assumption of the Theory of Relativity. It is made to describe even a universe with one particle. It happens to agree with the empirical evidence, which is why this assumption is accepted. I'm afraid I assume the same thing at the moment. I'm still trying to figure that one out.
But I am afraid the devil here in the details Very true. However, I believe that the truth is knowable, eventually, and will keep slogging after it.
Perhaps I should put some effort into putting my money where my mouth is. I would be lying if I said I flawlessly understood the above definition. So, again, can you recommend a good source to read up on these devilish details? Thanks.
Yours is not. You freely use the terms "dimension" and "linearity." Both terms are well defined, and neither you nor I are free to change those. For easy reference, I stated the definition of dimensionality. Regrettably, you don't even bother to utilize it. I am not going to help you further: I believe linearity is defined in any book on calculus.
It is perfectly fine not to know something (my own knowledge, G-d knows, is very limited). But one should not continue to throw around fancy words even after it has been discovered that they do not make any sense whatsoever. This may work in a quasi-intellectual discussion at Starbucks, not in science.
Regards, TQ.
In your article, you state "Then, in 1998, an international group, made up of six scientists and centered at the University of Innsbruck, proved that classical teleportation was possible, but at the moment only possible for photons and electrons. We won't be able to teleport ourselves in the near future, but it is not impossible that one day we might be able to.
Since there is at least one Physicist who considers time non existant, (I forget his name, there was a discussion about this on FR some time ago) that what we perceive as time is a similar effect to a moving picture, made up of many instantaneous "photographs". I believe his theorem was that we all exist in the "here and now", and that a sheaf of "here and nows" creates the phenomenon that we know of as time, then, using this as a model, human teleportation should be possible.
I would believe this is in the same theoretical class as the "multiple universes", in which every time someone makes a choice, no matter how insignificant, there is a parallel reality(ies) formed in which all permutations of the event occur. IF this were the case, then the "snapshot" of the you that is present "here and now" could be teleported. The problem is, as I see it, returning to the original place of teleportation, as that particular place has ceased to exist.
This explanation of the question may not make a heck of a lot of logical sense, but it is the best way I can come up with a description of how the procedure could be carried out without violating Heisenberg.
As always, comments, suggestions, and flames welcomed.
Keep the Faith for Freedom
Greg
Bump for later...After sex.
/john
I thought the M&M experiments proved that there was no ether. (er... failed to prove that the ether exists)
Correct. Santa --- yes; ether -- no.
Would tuned circuit coupling be a semi-valid analogy? But that implies a field.
Sigh. I should have stayed in school.
/john
Sigh. I should have stayed in school. It's a no-win situation, kd5cts: I did stay in school --- they made me teach classes.
No, just an iron.
/john
/john
An old man is walking in the street and talking to himself. His neighbor asks, "Why are you talking to yourself?" He answers, "I always enjoy speaking with an intelligent person."
I love to nibble at the edges of physics, but I have too many interests to immerse myself in it. Besides, I not sure I could understand what Fairbank, et al. actually proved without a real instructor to explain it. My eyes cross when I start reading about fractional charges. I appreciate your input to this thread tonight. You hvae been most instructive.
/john
Einstein did a gedanken but materials technology wasn't there then. We have it now. It shouldn't actually be that expensive to try. (plus or minus a few million)
/john
Not suprisingly, I, my best friend, and the user of the phrase were the only ones at the table who knew what "esoteric" meant. Aaaah.
Thanks for you kind words, I too enjoyed our "conversation."
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