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Quantum Teleportation Between Distant Matter Qubits: First Between Atoms 1 Meter Apart
by Science Daily
Thanks to GP for the link.
Reposted from:
http://www.sciencedaily.com/releases/2009/01/090122141137.htm
Single photons emitted by each of the ions are routed through optical fibers to a beamsplitter in which any arriving photon has a 50-50 chance of passing through or reflecting off. Before hitting the splitter, each photon is in a superposition of red and blue colors. When photons emerge from different sides of the beamsplitter, however, they are forced into opposite states -- red/blue or blue/red -- at random. In this case, each detector will record a photon at the same time -- one red and one blue. But it is impossible to know which ion produced which photon. A blue photon in the left detector, for example, could have come from Ion A and been reflected at the splitter. Or it could have come from Ion B and passed directly through. This fundamental uncertainty projects the ions into an entangled state, a condition immediately signaled by the simultaneous detection of two photons. (Credit: Image courtesy of University of Maryland)
ScienceDaily (Jan. 23, 2009) — For the first time, scientists have successfully teleported information between two separate atoms in unconnected enclosures a meter apart – a significant milestone in the global quest for practical quantum information processing.
Teleportation may be nature's most mysterious form of transport: Quantum information, such as the spin of a particle or the polarization of a photon, is transferred from one place to another, without traveling through any physical medium. It has previously been achieved between photons over very large distances, between photons and ensembles of atoms, and between two nearby atoms through the intermediary action of a third. None of those, however, provides a feasible means of holding and managing quantum information over long distances.
Now a team from the Joint Quantum Institute (JQI) at the University of Maryland (UMD) and the University of Michigan has succeeded in teleporting a quantum state directly from one atom to another over a substantial distance. That capability is necessary for workable quantum information systems because they will require memory storage at both the sending and receiving ends of the transmission.
In the Jan. 23 issue of the journal Science, the scientists report that, by using their protocol, atom-to-atom teleported information can be recovered with perfect accuracy about 90% of the time – and that figure can be improved.
"Our system has the potential to form the basis for a large-scale 'quantum repeater' that can network quantum memories over vast distances," says group leader Christopher Monroe of JQI and UMD. "Moreover, our methods can be used in conjunction with quantum bit operations to create a key component needed for quantum computation." A quantum computer could perform certain tasks, such as encryption-related calculations and searches of giant databases, considerably faster than conventional machines. The effort to devise a working model is a matter of intense interest worldwide.
Teleportation works because of a remarkable quantum phenomenon, called "entanglement," which only occurs on the atomic and subatomic scale. Once two objects are put in an entangled state, their properties are inextricably entwined. Although those properties are inherently unknowable until a measurement is made, measuring either one of the objects instantly determines the characteristics of the other, no matter how far apart they are.
The JQI team set out to entangle the quantum states of two individual ytterbium ions so that information embodied in the condition of one could be teleported to the other. Each ion was isolated in a separate high-vacuum trap, suspended in an invisible cage of electromagnetic fields and surrounded by metal electrodes. [See illustrations.] The researchers identified two readily discernible ground (lowest energy) states of the ions that would serve as the alternative "bit" values of an atomic quantum bit, or qubit.
Conventional electronic bits (short for binary digits), such as those in a personal computer, are always in one of two states: off or on, 0 or 1, high or low voltage, etc. Quantum bits, however, can be in some combination, called a "superposition," of both states at the same time, like a coin that is simultaneously heads and tails – until a measurement is made. It is this phenomenon that gives quantum computation its extraordinary power.
At the start of the experimental process, each ion (designated A and B) is initialized in a given ground state. Then ion A is irradiated with a specially tailored microwave burst from one of its cage electrodes, placing the ion in some desired superposition of the two qubit states – in effect writing into memory the information to be teleported.
Immediately thereafter, both ions are excited by a picosecond (one trillionth of a second) laser pulse. The pulse duration is so short that each ion emits only a single photon as it sheds the energy gained from the laser pulse and falls back to one or the other of the two qubit ground states. Depending on which one it falls into, each ion emits a photon whose color (designated red and blue) is perfectly correlated with the two atomic qubit states. It is this entanglement between each atomic qubit and its photon that will eventually allow the atoms themselves to become entangled.
The emitted photons are captured by lenses, routed to separate strands of fiber-optic cable, and carried into opposite sides of a 50-50 beamsplitter where it is equally probable for either photon to pass straight through the splitter or to be reflected. On either side of the beamsplitter output are detectors that can record the arrival of a single photon.
Before reaching the beamsplitter, each photon is in a superposition of states. After encountering the beamsplitter, four color combinations are possible: blue-blue, red-red, blue-red and red-blue. In nearly all of those variations, the photons cancel each other out on one side and both end up in the same detector on the other side. But there is one – and only one – combination in which both detectors will record a photon at exactly the same time.
In that case, however, it is physically impossible to tell which ion produced which photon because it cannot be known whether the photon arriving at a detector passed through the beamsplitter or was reflected by it.
Thanks to the peculiar laws of quantum mechanics, that inherent uncertainty projects the ions into an entangled state. That is, each ion is in a correlated superposition of the two possible qubit states. The simultaneous detection of photons at the detectors does not occur often, so the laser stimulus and photon emission process has to be repeated many thousands of times per second. But when a photon appears in each detector, it is an unambiguous signature of entanglement between the ions.
When an entangled condition is identified, the scientists immediately take a measurement of ion A. The act of measurement forces it out of superposition and into a definite condition: one of the two qubit states. But because ion A's state is irreversibly tied to ion B's, the measurement of A also forces B into a complementary state. Depending on which state ion A is found in, the researchers now know precisely what kind of microwave pulse to apply to ion B in order to recover the exact information that had originally been stored in ion A. Doing so results in the accurate teleportation of the information.
What distinguishes this outcome as teleportation, rather than any other form of communication, is that no information pertaining to the original memory actually passes between ion A and ion B. Instead, the information disappears when ion A is measured and reappears when the microwave pulse is applied to ion B.
"One particularly attractive aspect of our method is that it combines the unique advantages of both photons and atoms," says Monroe. "Photons are ideal for transferring information fast over long distances, whereas atoms offer a valuable medium for long-lived quantum memory. The combination represents an attractive architecture for a 'quantum repeater,' that would allow quantum information to be communicated over much larger distances than can be done with just photons. Also, the teleportation of quantum information in this way could form the basis of a new type of quantum internet that could outperform any conventional type of classical network for certain tasks."
The Joint Quantum Institute is a partnership effort between the National Institute of Standards and Technology and UMD, with additional support from the Laboratory for Physical Science. The work reported in Science was supported by the Intelligence Advanced Research Project Activity program under U.S. Army Research Office contract, the National Science Foundation (NSF) Physics at the Information Frontier Program, and the NSF Physics Frontier Center at JQI.
Adapted from materials provided by University of Maryland.
Reposted from:
http://www.sciencedaily.com/releases/2009/01/090122141137.htm
Single photons emitted by each of the ions are routed through optical fibers to a beamsplitter in which any arriving photon has a 50-50 chance of passing through or reflecting off. Before hitting the splitter, each photon is in a superposition of red and blue colors. When photons emerge from different sides of the beamsplitter, however, they are forced into opposite states -- red/blue or blue/red -- at random. In this case, each detector will record a photon at the same time -- one red and one blue. But it is impossible to know which ion produced which photon. A blue photon in the left detector, for example, could have come from Ion A and been reflected at the splitter. Or it could have come from Ion B and passed directly through. This fundamental uncertainty projects the ions into an entangled state, a condition immediately signaled by the simultaneous detection of two photons. (Credit: Image courtesy of University of Maryland)
ScienceDaily (Jan. 23, 2009) — For the first time, scientists have successfully teleported information between two separate atoms in unconnected enclosures a meter apart – a significant milestone in the global quest for practical quantum information processing.
Teleportation may be nature's most mysterious form of transport: Quantum information, such as the spin of a particle or the polarization of a photon, is transferred from one place to another, without traveling through any physical medium. It has previously been achieved between photons over very large distances, between photons and ensembles of atoms, and between two nearby atoms through the intermediary action of a third. None of those, however, provides a feasible means of holding and managing quantum information over long distances.
Now a team from the Joint Quantum Institute (JQI) at the University of Maryland (UMD) and the University of Michigan has succeeded in teleporting a quantum state directly from one atom to another over a substantial distance. That capability is necessary for workable quantum information systems because they will require memory storage at both the sending and receiving ends of the transmission.
In the Jan. 23 issue of the journal Science, the scientists report that, by using their protocol, atom-to-atom teleported information can be recovered with perfect accuracy about 90% of the time – and that figure can be improved.
"Our system has the potential to form the basis for a large-scale 'quantum repeater' that can network quantum memories over vast distances," says group leader Christopher Monroe of JQI and UMD. "Moreover, our methods can be used in conjunction with quantum bit operations to create a key component needed for quantum computation." A quantum computer could perform certain tasks, such as encryption-related calculations and searches of giant databases, considerably faster than conventional machines. The effort to devise a working model is a matter of intense interest worldwide.
Teleportation works because of a remarkable quantum phenomenon, called "entanglement," which only occurs on the atomic and subatomic scale. Once two objects are put in an entangled state, their properties are inextricably entwined. Although those properties are inherently unknowable until a measurement is made, measuring either one of the objects instantly determines the characteristics of the other, no matter how far apart they are.
The JQI team set out to entangle the quantum states of two individual ytterbium ions so that information embodied in the condition of one could be teleported to the other. Each ion was isolated in a separate high-vacuum trap, suspended in an invisible cage of electromagnetic fields and surrounded by metal electrodes. [See illustrations.] The researchers identified two readily discernible ground (lowest energy) states of the ions that would serve as the alternative "bit" values of an atomic quantum bit, or qubit.
Conventional electronic bits (short for binary digits), such as those in a personal computer, are always in one of two states: off or on, 0 or 1, high or low voltage, etc. Quantum bits, however, can be in some combination, called a "superposition," of both states at the same time, like a coin that is simultaneously heads and tails – until a measurement is made. It is this phenomenon that gives quantum computation its extraordinary power.
At the start of the experimental process, each ion (designated A and B) is initialized in a given ground state. Then ion A is irradiated with a specially tailored microwave burst from one of its cage electrodes, placing the ion in some desired superposition of the two qubit states – in effect writing into memory the information to be teleported.
Immediately thereafter, both ions are excited by a picosecond (one trillionth of a second) laser pulse. The pulse duration is so short that each ion emits only a single photon as it sheds the energy gained from the laser pulse and falls back to one or the other of the two qubit ground states. Depending on which one it falls into, each ion emits a photon whose color (designated red and blue) is perfectly correlated with the two atomic qubit states. It is this entanglement between each atomic qubit and its photon that will eventually allow the atoms themselves to become entangled.
The emitted photons are captured by lenses, routed to separate strands of fiber-optic cable, and carried into opposite sides of a 50-50 beamsplitter where it is equally probable for either photon to pass straight through the splitter or to be reflected. On either side of the beamsplitter output are detectors that can record the arrival of a single photon.
Before reaching the beamsplitter, each photon is in a superposition of states. After encountering the beamsplitter, four color combinations are possible: blue-blue, red-red, blue-red and red-blue. In nearly all of those variations, the photons cancel each other out on one side and both end up in the same detector on the other side. But there is one – and only one – combination in which both detectors will record a photon at exactly the same time.
In that case, however, it is physically impossible to tell which ion produced which photon because it cannot be known whether the photon arriving at a detector passed through the beamsplitter or was reflected by it.
Thanks to the peculiar laws of quantum mechanics, that inherent uncertainty projects the ions into an entangled state. That is, each ion is in a correlated superposition of the two possible qubit states. The simultaneous detection of photons at the detectors does not occur often, so the laser stimulus and photon emission process has to be repeated many thousands of times per second. But when a photon appears in each detector, it is an unambiguous signature of entanglement between the ions.
When an entangled condition is identified, the scientists immediately take a measurement of ion A. The act of measurement forces it out of superposition and into a definite condition: one of the two qubit states. But because ion A's state is irreversibly tied to ion B's, the measurement of A also forces B into a complementary state. Depending on which state ion A is found in, the researchers now know precisely what kind of microwave pulse to apply to ion B in order to recover the exact information that had originally been stored in ion A. Doing so results in the accurate teleportation of the information.
What distinguishes this outcome as teleportation, rather than any other form of communication, is that no information pertaining to the original memory actually passes between ion A and ion B. Instead, the information disappears when ion A is measured and reappears when the microwave pulse is applied to ion B.
"One particularly attractive aspect of our method is that it combines the unique advantages of both photons and atoms," says Monroe. "Photons are ideal for transferring information fast over long distances, whereas atoms offer a valuable medium for long-lived quantum memory. The combination represents an attractive architecture for a 'quantum repeater,' that would allow quantum information to be communicated over much larger distances than can be done with just photons. Also, the teleportation of quantum information in this way could form the basis of a new type of quantum internet that could outperform any conventional type of classical network for certain tasks."
The Joint Quantum Institute is a partnership effort between the National Institute of Standards and Technology and UMD, with additional support from the Laboratory for Physical Science. The work reported in Science was supported by the Intelligence Advanced Research Project Activity program under U.S. Army Research Office contract, the National Science Foundation (NSF) Physics at the Information Frontier Program, and the NSF Physics Frontier Center at JQI.
Adapted from materials provided by University of Maryland.
Comments 1 - 50 of 67 |
Reload Comments | Back to Top | Page Numbers2. Comment #326692 by gazzaofbath on January 23, 2009 at 3:10 pm
I still don't see how meaningful information is transferred here. I thought that was the situation with entanglement.
If ion 'A's state is known then it's possible to interrogate ion 'B' correctly to get the information on 'A'. Is any new information obtained from this interrogation of 'B'? It's not clear to me - help!
Other Comments by gazzaofbath
3. Comment #326718 by alexo on January 23, 2009 at 4:23 pm
I think Feynman explained it best; " if you think you understand quantum mechanics... etc etc. Always a pleasure to read articles such as this and realise in some areas we are not all equal much as though we would like to be. At school I loved physics but hated maths, how cruel! Excelled at Biology though. Other Comments by alexo
4. Comment #326752 by Vergil on January 23, 2009 at 5:27 pm
Quantum physics make me feel a certain sympathy for Newton's contemporaries: "What do you mean an object keeps moving unless a force is applied to it' That goes against common sense!" And Darwin's: "What do you mean animals 'change'' That goes against common sense!" Now Newtonian physics seems like the common sense we've all grown to accept, and which quantum rules have turned on its head...Other Comments by Vergil
5. Comment #326757 by theantitheist on January 23, 2009 at 5:39 pm
Turning things on their heads makes me dizzy Hopefully they can work this into laymans terms soon
Other Comments by theantitheist
6. Comment #326759 by vega on January 23, 2009 at 5:45 pm
Old news. See the Koran 6:39...:) Other Comments by vega
7. Comment #326764 by AshtonBlack on January 23, 2009 at 6:19 pm
A good starting point to understand (or a least get a handle on what they are talking about) entanglement is:http://www.amazon.com/Entanglement-Greatest-Amir-D-Aczel/dp/1568582323
I bought the audio book from itunes... it's very accessible to the layman like me.
Other Comments by AshtonBlack
8. Comment #326767 by Muetze on January 23, 2009 at 6:37 pm
http://xkcd.com/465/ Other Comments by Muetze
9. Comment #326770 by Ian Bamlett on January 23, 2009 at 7:05 pm
oh, we are so screwed now. Quantum processors... artificial intelligence.... your toaster taking over the world.. it all starts here. Other Comments by Ian Bamlett
10. Comment #326776 by tsacrey on January 23, 2009 at 7:44 pm
I just read another article on ScienceNewsDaily about how a scientist just invented the world's smallest switch where the contact is comprised of just a single atom of gold. In another article I just read a scientist had discovered a gene in a particular breed of fruit flies that, when modified, doubled their life span, apparently through the lessening of the production of free radicals in the body...so, hypothetically, if that could be developed into drug therapies for humans, we could live to be double our current life span! Oh, and the fruit flies didn't suffer any side effects of the gene manipulation either.At any rate, with the speed of technological and medical progress, it's hard to believe that anything could be out of the reach of humanity...with so much being unveiled to us every day, it still blows my mind how so many people remain happily ignorant of the fact that we ARE alone (in the spiritual sense), but that it's ok! We are getting better and better all the time at understanding our universe! Sheesh.
Other Comments by tsacrey
11. Comment #326778 by Ohnhai on January 23, 2009 at 7:52 pm
Is cool. though I'm still waiting to see how they come up with a way to entangle specific atoms/ions so that your communication device can cominucate with multiple systems and not just the other specific unit in the pre-entangled pair...is it possible to entangle the atoms/ions of a pair of units once they are separated by long distance? how do you precisely sync these two units to set up this quantum link.
or will each unit already contain a massively entangled atom/ion that is entangled with every other unit to start with, and information packets are simply encoded for decryption on a specific unique box and then sent swimming on the entangled net of particles?
Other Comments by Ohnhai
12. Comment #326782 by mmurray on January 23, 2009 at 8:43 pm
@gazzaofbathI agree. Any quantum mechanics in the house who can explain this to us ?
Michael
Other Comments by mmurray
13. Comment #326797 by robotaholic on January 23, 2009 at 9:50 pm
You quantum FREAKS please don't say a bunch of bullshit- gosh - Other Comments by robotaholic
14. Comment #326815 by Laurie Fraser on January 23, 2009 at 11:39 pm
Brilliant. Freaky, but brilliant. Thanks for posting. Other Comments by Laurie Fraser
15. Comment #326825 by clarityofthought on January 24, 2009 at 1:01 am
A physicist named William Heisenberg [he of the 'Uncertainty Principle'] when asked how an atom could be envisioned, supposedly replied "Don't try". I am in awe & can only genuflect to those experts who can speak Quantumese!
Other Comments by clarityofthought
16. Comment #326934 by Roland_F on January 24, 2009 at 5:55 am
Comment #326692 by gazzaofbath : If ion 'A's state is known then it's possible to interrogate ion 'B' correctly to get the information on 'A'. Is any new information obtained from this interrogation of 'B'? It's not clear to me - help!
Comment #326782 by mmurray : @gazzaofbath
I agree. Any quantum mechanics in the house who can explain this to us ?
The entanglement can be used in quantum computing and every single atom entangled can be used for processing Qbits. Processing power of Quantum computers per 'n' atoms is 2**n, so entanglement of 30 or so atoms are equivalent to current CPU power levels. Current quantum computers have 8 atoms entangled.
There are a couple of public lectures of Perimeter institute available on video streamer about the topic.
Quantum teleportation from Anton Zeilinger:
http://.perimeterinstitute.ca/mediasite/viewer/?peid=a562d25a-9999-455b-ac95-da0bc01002b6
About quantum computers (only need short distance entanglement) :
http://streamer.perimeterinstitute.ca/mediasite/viewer/NoPopupRedirector.aspx?peid=34741d81-cb29-43a7-a09b-b2238f766599&shouldResize=False
http://streamer.perimeterinstitute.ca/mediasite/viewer/NoPopupRedirector.aspx?peid=699564dd-6475-43a3-ba0d-f8442ef95e16&shouldResize=False
For long distance entanglement this can be used for Quantum cryptography as any attempt of “listening” into conversation would influence the result of information which would be then detected that the connection security is breached.
http://streamer.perimeterinstitute.ca/mediasite/viewer/?peid=d58f3c28-5f45-4ed2-9d0d-db0b6b91ddef
Other Comments by Roland_F
17. Comment #326970 by sublunary on January 24, 2009 at 10:00 am
The problems that quantum mechanics cause for primate brains are due to our familiarity with events within certain scales - those of size and time. Generally when we learn or teach something new we do so with reference to what is already understood by ourselves or our audience. And so, with this in mind, Bohr described the atom as a mini solar-system. Which, of course, it is not. Photons, electrons and other fundamental particles are often considered as particles in the normal sense of the word, the sense we understand when thinking about billiard balls. Once again, the fundamental particles are not particles in this sense.So what can we do to understand this aspect of nature so divorced from our experiences? The simple answer is to re-educate our brains, and that tricky task is accomplished, in the case of much of physics, with mathematics. To explain quantum teleportation outside of Star Trek requires an understanding of the concept of quantum entanglement. To understand quantum entanglement (and I'm using the word "understand" in a sense that implies an ability to model and make predictions, not a genuine experiential understanding) requires a knowledge of the ideas of vector spaces. These can be understood in contrast to the usual concept of state spaces. So now we have to understand what a state space is. The good news is: a state space yields to "normal" descriptions, so it is a good place to begin.
These are the tools used to re-educate our brains to think about such "crazy" things, and I doubt that any satisfying explanation can be offered in a summarised form. Feynman famously set himself the task of explaining QED (Quantum Electrodynamics) to a lay audience in the late 70's - it took his genius four lectures. So for anyone with patience, I'd highly recommend his subsequent book of those lectures or the lectures themselves. The lectures can be found about half-way down the page here.
Unfortunately, with regards to this article, Feynman doesn't discuss entanglement!
For those with even greater patience, there's an excellent and thorough series of lectures (about 16 hours) on the subject of quantum entanglement given by Leonard Susskind at Stanford, available through iTunesU: quantum entanglement
Other Comments by sublunary
18. Comment #326983 by sublunary on January 24, 2009 at 10:47 am
This experiment is an extension of earlier work, notably that of Zeilinger. Removing the experimental details, it can be described in slightly simpler terms.Two particles, A and B are entangled. The state of A is unknown, as is the state of B. Let's imagine that we arrange to measure A in such a way that its state, for example its spin, is either up or down. Until it's measured, it is neither up nor down but is described by its vector state - roughly what superposition is being used to describe in this article. In this state, it has a known probability of being up (or down), that probability being deduced from the way in which it has been prepared.
Let's suppose we arrange for the entanglement between A and B to be such that they are opposite. If A is up, B is down. This is an experimental detail and is relatively simple for electrons, for example, since they like to pair in this opposite sense. So, we now have A in an unmeasured (vector) state, and B in a complementary state. Once we measure A, it becomes either up or down implying that B is down or up. No information is carried between A and B, rather they each carried information about their entanglement until one or the other was measured.
A slightly poor analogy might be to think about finding yourself outside on a cold day, looking through your pockets for your gloves but only finding one. Knowing that you have only one glove, once you realise it is the left glove you immediately know that it is the right glove that is in your other coat. No information has passed between your gloves but their left-right entanglement means that knowing the one in your hand is "left" implies the one in your other coat is "right".
Next time, check before you leave the house.
Other Comments by sublunary
19. Comment #326984 by Evilcor on January 24, 2009 at 10:48 am
So how are we supposed to turn this into a weapon? I'm sorry, I just can't get interested until we can teleport cyanide into somebody's bloodstream, or something. Other Comments by Evilcor
20. Comment #326986 by mcarp on January 24, 2009 at 10:52 am
"Depending on which state ion A is found in, the researchers now know precisely what kind of microwave pulse to apply to ion B in order to recover the exact information that had originally been stored in ion A."But doesn't that mean that the information is transferred by the act of the scientist knowing what microwave pulse to apply to B?
Other Comments by mcarp
21. Comment #326991 by sublunary on January 24, 2009 at 11:11 am
Comment #326986 by mcarp
But doesn't that mean that the information is transferred by the act of the scientist knowing what microwave pulse to apply to B?
I think that in the way this has been described, you are correct. However, in general the information encoded in A is recoverable at distance by interrogating B without knowing the state of A. Perhaps that is a technical detail to be resolved or perhaps the reporting is vague.
Other Comments by sublunary
22. Comment #326997 by nalfeshnee on January 24, 2009 at 11:35 am
I happily confess I do not understand this.But presumably it is a way for faster-than-light communication, is it not?
Method:
1. Entangle atoms in such a way that you can usefully find out some stuff once you disentangle them
2. Take one bunch to somewhere in solar system (e.g. moons of Jupiter)
3. Disentangle them and learn some stuff
Instantly.
The teleportation breaks the rule against faster-than-light travel - doesn't it?
Other Comments by nalfeshnee
23. Comment #327000 by jesusmasterbated on January 24, 2009 at 11:45 am
i also do not understand this, but i find it really cool that people are able to come up with all this cool shitOther Comments by jesusmasterbated
24. Comment #327002 by Eshto on January 24, 2009 at 11:48 am
Yeah I don't understand it either, I just assume it means some really kickass computers and cell phones in a few years. Other Comments by Eshto
25. Comment #327005 by sublunary on January 24, 2009 at 12:11 pm
Comment #326997 by nalfeshnee
The teleportation breaks the rule against faster-than-light travel - doesn't it?
In your example, you take stuff to a moon of Jupiter (or send it as photons). That is when the information is carried from the entangled source. When the measurement is done, you, the experimenter, then becomes entangled with the photons on the moon of Jupiter. No information has travelled faster than light.
If we use the language of wave-functions collapsing, locally to our Jovian experiment and simultaneously back on Earth, we might wrongly assume that something has travelled between the two instantly. That is a problem of the language. If instead we talk in terms of the information being carried from the entangled source to Jupiter, where we do the measurement, it is clear that the information travels in accordance with Einstein's ideas. As I mentioned in an earlier comment, our brains don't naturally do this kind of stuff, nor does our language.
Other Comments by sublunary
26. Comment #327008 by MadMonkey on January 24, 2009 at 12:34 pm
Ah... the rapture is one step closer Other Comments by MadMonkey
27. Comment #327010 by streamripper on January 24, 2009 at 12:42 pm
Comment #326986 by mcarp
But doesn't that mean that the information is transferred by the act of the scientist knowing what microwave pulse to apply to B?
Comment #326991 by sublunary
I think that in the way this has been described, you are correct. However, in general the information encoded in A is recoverable at distance by interrogating B without knowing the state of A. Perhaps that is a technical detail to be resolved or perhaps the reporting is vague.
I don't think that's the right answer. I think the point is that you can use the transmission of ordinary classical information (which pulse should be applied to B) in order to cause the transmission (but not duplication) of quantum information.
Remember, we're trying to teleport a quantum state, which is a very different beast from ordinary classical information. You can't measure the actual state vector of a quantum system, which is the thing being teleported. (You can make a measurement, but that destroys the state vector and gives you one of the eigenstates.)
The Wikipedia article on quantum teleportation is pretty good:
http://en.wikipedia.org/wiki/Quantum_teleportation
Other Comments by streamripper
28. Comment #327022 by -dr- on January 24, 2009 at 1:40 pm
Decent graphics but kinda mediocre audio.http://ca.youtube.com/watch?v=_qmSdC7aQpY
Perhaps sublunary can pronounce upon its scientific accuracy.
Other Comments by -dr-
29. Comment #327080 by bachfiend on January 24, 2009 at 2:50 pm
I was going to protest that this couldn't possibly be true as it wasn't ever mentioned in some thousands years old text, but vega (comment #6) has stolen my thunder. If only I could understand what "[6.39] And they who reject Our communications are deaf and dumb, in utter darkness; whom Allah pleases He causes to err and whom He pleases He puts on the right way".I don't know what it means too. I think I will take a headache tablet and go to bed and try to sleep it away.
I heard on the "Sceptics Guide to the Galaxy" this morning that there is a new hypothesis that the Universe is a hologram of the information on the surface of the visible Universe, So if a dot on the surface has a size of Planck length (1.6 x 10 the minus 35 metres approximately), it corresponds to a dot in the Universe which by necessity has to be much larger, and hence the Universe is much "grainier".
It apparently will explain which string theory or membrane theory will be correct. I just hope it will explain how many dimensions there are. I have trouble just trying to imagine 5, let alone 10 or 11.
Other Comments by bachfiend
30. Comment #327103 by Shergar on January 24, 2009 at 3:31 pm
Doctor.... my brain hurts !! Other Comments by Shergar
31. Comment #327132 by streamripper on January 24, 2009 at 4:13 pm
Comment #327113 by Foxy
When the state of particle A is changed, the state of particle B is changed simultaneously. This means that the information is traveling faster than the speed of light.
Well, I think information is not really the right word. Perhaps nonlocal influence would be a better description.
You can't use entanglement to transmit information, because when you measure particle A you can't choose the result you get. There's no way to arrange to measure particle A in a way that would convey information to a person later measuring particle B.
Other Comments by streamripper
32. Comment #327221 by NewEnglandBob on January 24, 2009 at 8:15 pm
29. Comment #327080 by bachfiend:...
I heard on the "Sceptics Guide to the Galaxy" this morning that there is a new hypothesis that the Universe is a hologram of the information on the surface of the visible Universe, So if a dot on the surface has a size of Planck length (1.6 x 10 the minus 35 metres approximately), it corresponds to a dot in the Universe which by necessity has to be much larger, and hence the Universe is much "grainier".
It apparently will explain which string theory or membrane theory will be correct. I just hope it will explain how many dimensions there are. I have trouble just trying to imagine 5, let alone 10 or 11.
This is not new stuff. It has been around several years and called the Holographic principle. Among other places, it is in the book:
Hiding In The Mirror: The Mysterious Allure of Extra Dimensions, from Plato to String Theory and Beyond
By Lawrence M. Krauss - published November, 2006
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33. Comment #327223 by TuftedPuffin on January 24, 2009 at 9:16 pm
To clear up some things:Quantum teleportation requires that some information be transferred in a perfectly normal way, at less than the speed of light. The reason why such a procedure is more useful than simply transferring the information seems, from what I get of the wikipedia article, to be because normally you cannot transmit a quantum state from one place to another simply by sending classical information. You need the entangled state helping you to set up the quantum state you want on the other side. This makes it useful in quantum computing, where information is stored not classically, but in quantum states.
As for whether it breaks special relativity, it does and it doesn't. Quantum mechanics is indeed nonlocal: measuring one thing in an entangled pair will immediately cause the other's wavefunction to collapse, no matter the distance between them. You can't actually use this to transmit useful information, however, since you can't control the result of your measurement, so you can't cause any interesting time travel paradoxes.
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34. Comment #327229 by Lucas on January 24, 2009 at 11:10 pm
Many thanks to the knowledgeable. Some of the comments here are more enlightening than the article. Other Comments by Lucas
35. Comment #327348 by streamripper on January 25, 2009 at 7:11 am
Comment #327229 by Lucas
Some of the comments here are more enlightening than the article.
Yes, I think TuftedPuffin's summary is quite lucid. Typically you can learn ten times as much information from Wikipedia as from a popular science article. (Or in some cases, -10 times as much!) This article is not bad, though, in my opinion.
Comment #327223 by TuftedPuffin
measuring one thing in an entangled pair will immediately cause the other's wavefunction to collapse
You could say that the two particles share a wavefunction (more precisely, they occupy an inseparable state), so that when you do anything (like a measurement) that causes decoherence of that shared wavefunction, the effect on both particles is evident.
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36. Comment #327473 by inkling on January 25, 2009 at 9:37 am
I also fail to see how true "information" is being transmitted in anything but a impractical philosophical way...Here is my question/metaphor:
Two scientists, with this device, are in separate adjacent rooms, and they each have access to one one the entangled particles. Scientist "A" has a safe in his room, and the combination is either 1 or 0.
(Lets make it more interesting and say that if he gets the code WRONG, a bomb goes off.)
Now, Scientist "B", in the other room, KNOWS what the password is. How would he go about "telling" Scientist "A" what the password is using entangled particles, without either scientist leaving the room?
If he cannot do this, then... what's the point?
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37. Comment #327514 by streamripper on January 25, 2009 at 10:34 am
Comment #327473 by inkling
How would he go about "telling" Scientist "A" what the password is using entangled particles, without either scientist leaving the room?
He wouldn't. If the password is 0 or 1, that's classical information, and we already have very good ways of transmitting it.
Being able to teleport quantum states is valuable for quantum computation (which is not yet fully realized). It's like how in an ordinary computer you have to be able to move bits around, except quantum bits (qubits) require special care. It sounds crazy, but you can do some amazing things with a quantum computer that you can't do with a classical one. Unfortunately there are still various barriers to the construction of a large-scale quantum computer.
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38. Comment #327564 by gazzaofbath on January 25, 2009 at 12:08 pm
Sublumary in his posts has explained entanglement in the way I thought I understood it. A fascinating and spooky non-local phenomenon but not a process that can be used practically to communicate useful information faster than the speed of light, so compatible with relatively.
I still don't understand the implications of this particular article. But Roland_F and others indicate it's more to do with quantum computing than faster than light communication (sorry Roland_F- I haven't read/listened to your references yet). So still some understanding for me to do.....
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39. Comment #327612 by TuftedPuffin on January 25, 2009 at 2:12 pm
To continue the scientist/password analogy, imagine that instead of the password being 1 or 0, it's a quantum superposition of 1 and 0. Scientist "B" doesn't "know" the password, but he's got an object that's in the same superposition as the password is. Scientist "B" can't just measure the superposition and send that information (via walky-talky, let's say) to Scientist "A", because if he did, he would only be sending one possible measurement, not the full superposition. The only way to send the superposition is to use entangled states and quantum teleportation. And yes, that still requires a walky-talky, but the point is without entanglement, even with a walky-talky you can't do it. If you replace Scientists "A" and "B" with two different sides of a quantum computer you get a sense of the use this could be put to.And yes, sharing a wavefunction is a better way of describing it than having one wavefunction affect the other...but there's still the "problem" that one wavefunction is responding to a measurement in one place and instantaneously changing its properties as measurable at a distant place...no matter what, you've still got spooky action at a distance.
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40. Comment #327625 by Francis Clarke on January 25, 2009 at 2:28 pm
This sort of thing is maddeningly confusing. Here they say that information has been teleported, then I hear it's impossible to tramsmit information across entangled particles. If that is so, then how can anything be teleported at all, and how can this help create quantum computers?41. Comment #327612 by TuftedPuffin
The scientists could just use the walky-talky to tell the password to each other and the whole quantum stuff would be useless.
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41. Comment #327626 by streamripper on January 25, 2009 at 2:33 pm
then I hear it's impossible to transmit information across entangled particles
Insert the words "faster than the speed of light". :^)
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42. Comment #327632 by streamripper on January 25, 2009 at 2:55 pm
but there's still the "problem" that one wavefunction is responding to a measurement in one place and instantaneously changing its properties as measurable at a distant place...no matter what, you've still got spooky action at a distance.
I agree completely that it's still spooky and mystifying, but perhaps just a tiny bit less so when phrased this way. <grin>
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43. Comment #327872 by Francis Clarke on January 26, 2009 at 8:30 am
So if you can still transmit information across entangled particles, but it's slower than the speed of light, why is this even useful in quantum computing? Why not use classical technology to do the same thing at the same speed? Other Comments by Francis Clarke
44. Comment #327876 by MadMonkey on January 26, 2009 at 8:37 am
44. Comment #327632 by streamripper
I see no problem. Bring it on...
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45. Comment #327919 by streamripper on January 26, 2009 at 9:45 am
Why not use classical technology to do the same thing at the same speed?
Classical technology can't do the same thing. Quantum computers manipulate qubits, which are fundamentally different from bits. For example, Shor's integer factoring algorithm and Grover's database search algorithm take advantage of this. See previous comments for Wikipedia links.
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46. Comment #327944 by DiveMedic on January 26, 2009 at 10:54 am
So I spend all this time acing premed courses and then nursing courses (when having a kid screwed up my med school plans.... that little twirp) trying to make myself feel smart and then I read crap like this.I am very glad that so many of you don't understand this because I felt like when I was reading this article, I was reading Chinese. And my Chinese is about as good as my Martian.
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47. Comment #327949 by Pyroclast on January 26, 2009 at 11:05 am
Somehow, somewhere in this multydimensional universe, the entagled particles are "one", therfore, if you change the spin of one, the other also changes at the same time. In this way, there is no information traveling anywere at any speed and Einstein would be happy.Other Comments by Pyroclast
48. Comment #328155 by PsyPro on January 26, 2009 at 11:27 pm
The problem with all of the ``explanations'' offered here is that they miss the essential nature of the claims being made in the original article. For example, although the left-behind glove is often offered as an analogy (even if forewarned as a poor one), it is not an analogy at all.
As conceived, it is the *measurement* of one of the particle's vector states (i.e., whether the glove at hand *becomes* or takes on the state of, as a result of that measurement, a left- or right-hand glove) that determines the subsequently measured (``known?'') state of the entangled particle (i.e., the handedness of the left-behind glove. It wasn't in any such state *before* that measurement.) But, because according to quantum theory, the originally measured particle could take on either vector state with equal probability (or whatever the probabilities were in the actual experiment) when forced to (i.e., ``measured''). The key assumption (claim? assertion?) of quantum physics is that it is the act of measurement that forces the result, not any pre-existing state. Hence, if the vector state did not and could not pre-exist the measurement, the fact that it now predicts the state of the entangled particle implies that there must *in some sense* be ``information'' ``teleported'' between them. Both of the scare-quoted terms also need very careful explication.
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49. Comment #328747 by Philster61 on January 27, 2009 at 11:12 pm
CoolOther Comments by Philster61
50. Comment #330418 by polestar on January 30, 2009 at 2:24 pm
The only known conscious force that can deliberately affect nature is Mankind: does that make us gods?Hang on.
Nope, I can't stop the sun or bring down city walls. What a pity.
Still, it's a fun notion to tease the fundies with.
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1. Comment #326682 by dochmbi on January 23, 2009 at 2:55 pm
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