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Quantum Teleportation and Computation

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.


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To: Father Wu
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%.

In a related experiment, the use of HUP to alter what exists at another location via this calcite photon-splitting process is mind-blowing. Split the photon, measure it in one location, and alter the form of its double in the other, remote location. At the least, it's a capability for FTL communication...once the beam of split photons reach the ends of the transmission path.

141 posted on 12/20/2001 6:07:26 PM PST by lepton
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To: Nick Danger
LOL!
142 posted on 12/20/2001 6:08:32 PM PST by lepton
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To: lepton
who knew what "esoteric" meant.

I know what that means too. It's something Baptists don't approve. Shame on you. Bringing esotericism to a family forum. Next thing you know, we'll have pictures of Lithuanian fireplace designs on the thread.

/john

143 posted on 12/20/2001 6:10:43 PM PST by JRandomFreeper
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To: AUgrad
Don't Einstein's laws (using Quantum measures)

I seem to recall that Einstein referred to the above results in quantum mechanics as "spookiness from a distance". He agreed that the equations resulted in these types of answers, but refused to believe that they were real.

144 posted on 12/20/2001 6:13:16 PM PST by lepton
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To: palo verde;prentice;null and void;catpuppy
Oh boy, oh no...more things to consider as the day approaches.Palo, anything about this now?? LOL
145 posted on 12/20/2001 6:14:41 PM PST by habs4ever
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To: TopQuark
I think indirectly we do just that in particles accelerators.

I'm not thinking 10e-umpteen mass. I'm thinking 10e2 to 10e5 kg at 150K rpm and rotating around the center of mass, not orbiting.

I remember reading about an experiment with a large chunk of lead in an underground vault. And another with dry-cleaning fluid in an underground vault. Sheesh. I've got to go dig this stuff back up.

/john

146 posted on 12/20/2001 6:18:43 PM PST by JRandomFreeper
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To: FairWitness
On the other hand, at least some of what I have heard of quantum physics (which is admittedly not a lot) indicates that that is not necessarily true for elementary particle physics

One of the precepts of quantum mechanics is that "objects" don't really exist at a specific place, but could more reasonably be represented as probabilities centered around a certain area. If one cancels a probability in one place, that naturally increases the probability that the energy will exhibit itself somewhere else. This is kind of what the photon teleportation experiment appears to have done, by creating a barrier, sufficiently narrow that some small portion of the photon beam would mute itself to the other side of the barrier, and continue on its path, thereby arriving before it was expected.

147 posted on 12/20/2001 6:19:21 PM PST by lepton
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To: lafroste
At this point, science and philosophy will have to be reconciled

First they have to be addressing the same subject...then they have to define the terms the same way...then we can begin. :)

148 posted on 12/20/2001 6:20:56 PM PST by lepton
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To: Physicist; RadioAstronomer; PatrickHenry, longshadow, OBAFGKM; Gordian Blade; VadeRetro; js1138...
Self-referential bump for later reading.
149 posted on 12/20/2001 6:28:54 PM PST by Physicist
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To: Father Wu
Even with QT, we're still not able to break past the speed of light, because after the scanning process the information still has to be sent at light speed or slower

No, the particles to be interacted with have to get to both the manipulation point, and the receiving point, once that is done, information travel is at least twice the speed of light (I've yet to see whether HUPs alterations is instantaneous or at the speed of light from the original locations, so I can't say if it is faster than 2c).

150 posted on 12/20/2001 6:31:21 PM PST by lepton
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To: patrickhenry
placemarker
151 posted on 12/21/2001 2:48:31 AM PST by PatrickHenry
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To: TheEdge
"Refresh my memory. Didn't I read in Science News a little bit ago that scientists already 'teleported' a small frog (?)."

No, you're thinking of the experiment where someone magnetically levitated a frog in a metal tube.

152 posted on 12/21/2001 3:19:39 AM PST by Don Joe
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To: Father Wu
On this forum, when something in the world happens that is a mystery or is very important, or is esoteric-discussion of teleportation- the experts post. When flight 800 crashes with questions , witnesses post and people involved in the investigation, etc. Lawyers post with explanations of legal ramifications, insiders post, scientists and engineers can be relied on to post detailed explanations and directions to sources and background. FR is the best single source for details and explanations of just about any subject that comes up.
153 posted on 12/21/2001 4:04:26 AM PST by arthurus
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To: Father Wu
On this forum, when something in the world happens that is a mystery or is very important, or is esoteric-discussion of teleportation- the experts post. When flight 800 crashes with questions , witnesses post and people involved in the investigation, etc. Lawyers post with explanations of legal ramifications, insiders post, scientists and engineers can be relied on to post detailed explanations and directions to sources and background. FR is the best single source for details and explanations of just about any subject that comes up.
154 posted on 12/21/2001 4:05:13 AM PST by arthurus
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To: TopQuark
Look, I may not know everything, but just because you don't understand what I am saying or trying to say doesn't make me inconsistent.  For the record, I do understand the difference between linear and non-linear systems (after all, I did manage somehow to get through remedial calculus in reform school :).

IMHO, the spatial dimensions as we know them are linear whereas time is not.  Or rather I should say that time is only linear to the objects within a particular time frame (or time plane if you will).  But no two time frames are linear to each other.  The faster one time frame goes in relation to another, the slower the objects within the speedy time frame move (as perceived by the slower time frame).  OTOH, to the speedy time frame, the objects within the slower time frame speed up.  In both time frames, the local speed remains the same.  However, both time frames are using the same spatial dimensions.  The spatial dimensions are on a straight line that is not changed by acceleration, velocity, gravity, or anything that we know (IOW, both parties are part of the same universe).  However, time is affected by the speed you are travelling (basic assumption: The faster you are travelling, the slower time becomes - except when listening to Daschle, when time and belief become suspended in the worm-hole of vacuous stupidity).

This argues that time, as we know it, is probably best graphed by using an asymptotic curve, whereas the spatial dimensions are best described using lines.  Thus my assertion that time is non-linear and spatial dimensions are linear.  If you feel that time is linear in nature and is affected by velocity, that's fine, because it is only a theory yet unproven (although immensely popular and useful amongst the scientific set).  I apologize if my choice of wording is not quite correct.  After all, I am not a physicist.  Perhaps I should have said "Doppler affect" instead of "red-shift."  I still think my point is valid and that having a non-linear dimension as part of a set of linear dimensions makes for some difficulties in calculations.

Which brings me to my last point.  Simply put, what would happen if you could convert the spatial dimensions within a given time-frame to the same non-linear system used by time?  Personally, I think that the affect might be similar to removing (or at least significantly compressing) one of the spatial dimensions.
155 posted on 12/21/2001 4:49:54 AM PST by Frumious Bandersnatch
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To: Physicist
Thanks for the bump. I have some catching up to do. :)
156 posted on 12/21/2001 7:27:39 AM PST by RadioAstronomer
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To: Physicist
A long time ago, I read an SF novel (might have been shorter than a novel) involving teleportation (there are thousands of such stories), but this one had the interesting feature that the person being teleported actually dies at the sending end, while the person who emerges at the other end is a duplicate with the same memories. So the emerging person is undisturbed by the death of his predecessor, because from his point of view he's the same person. But the poor devil going into the machine knows he's going to die. His only motivation is that he knows he's sending his duplicate off somewhere where he needs to go. The idea was well-developed. I don't remember the author, or even the plot, only that neat feature of the teleportation system.
157 posted on 12/21/2001 9:11:40 AM PST by PatrickHenry
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To: PatrickHenry
the interesting feature that the person being teleported actually dies at the sending end

Wasn't that Bones McCoy's basic objection to the transporter in Star Trek?

158 posted on 12/21/2001 9:30:34 AM PST by Physicist
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To: Physicist
Wasn't that Bones McCoy's basic objection to the transporter in Star Trek?

McCoy often expressed an anti-technological dislike of "having your molecules scattered all over space," but I never recall "transmit/die" as being part of the Star Trek technology. Perhaps a hard-core Trekkie can fill us in.

159 posted on 12/21/2001 11:42:08 AM PST by PatrickHenry
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To: Orual
Be confused. Be very confused.
160 posted on 12/21/2001 12:28:48 PM PST by CubicleGuy
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