New Type Of Entanglement Allows "Teleportation in Time", Say Physicists
Entanglement is the strange quantum phenomenon in which two or more particles become so deeply linked that they share the same existence.
That leads to some counterintuitive effects, in particular, when two entangled particles become widely separated. When that happens, a measurement on one immediately influences the other, regardless of the distance between them. This "spooky-action-at-a-distance" has profound implications about the nature of reality but a clear understanding of it still eludes physicists.
Today, they have something else to puzzle over. Jay Olson and Timothy Ralph at the University of Queensland in Australia say they've discovered a new type of entanglement that extends, not through space, but through time.
They begin by thinking about a simplified universe consisting of one dimension of space and one of time.
It's easy to plot this universe on a plane with the x-axis corresponding to a spatial dimension and the y-axis corresponding to time.
If you imagine the present as the origin of this graph, then the future (ie the space you can reach at subluminal speeds) forms a wedge that is symmetric about the y-axis. Your past (ie the space you could have arrived from at subluminal speeds) is a mirror image of this wedge reflected in the x-axis.
When two particles are present, both sitting on the x-axis, their wedges will overlap in the future and in the past. This has a simple meaning: these particles could have interacted in the past and could do so again in the future, but only in the areas of overlap.
Conventional entanglement cuts across this world, quite literally. It acts along the the x-axis, linking particles instantly in time and in defiance of the boundaries to these wedges.
What Olson and Ralph show is that entanglement can just as easily work along the y-axis too. In other words, entanglement is so deeply enmeshed in the universe that a measurement in the past has an automatic influence on the future.
That may sound like a truism. Isn't this is how the universe works, I hear you say. But this isn't ordinary cause and effect; there are some interesting subtleties to this phenomenon.
To see how, imagine an experiment that Ralph and Olson describe in which a qubit is sent into the future. The idea is that a detector acts on a qubit and then generates a classical message describing how this particle can be detected. Then, at some point in the future, another detector at the same position in space, receives this message and carries out the required measurement, thereby reconstructing the qubit.
But there's a twist. Olson and Ralph show that the detection of the qubit in the future must be symmetric in time with its creation in the past. "If the past detector was active at a quarter to 12:00, then the future detector must wait to become active at precisely a quarter past 12:00 in order to achieve entanglement," they say. For that reason, they call this process "teleportation in time".
But how is this different from ordinary existence? After all, we're all time travellers, moving into the future at the same rate. What's special about Olson and Ralph's route?
The answer is that Olson and Ralph's teleportation provides a shortcut into the future. What they're saying is that it's possible to travel into the future without being present during the time in between.
That's a fascinating scenario that immediately raises many questions. One of the first that springs to mind is what advantage might we get from this process. Might it be possible, for example, to make short-lived particles live longer by teleporting them into the future?
That isn't clear. Neither is it clear exactly how such an experiment might be done although. Presumably, it wouldn't be very different to the type of teleportation that is done in labs all over the world today, as a matter of routine (in fact Olson and Ralph say that timelike entangelment is interchangeable with the spacelike version).
Quote:Quantum teleportation has achieved a new milestone or, should we say, a new ten-milestone: scientists have recently had success teleporting information between photons over a free space distance of nearly ten miles, an unprecedented length. The researchers who have accomplished this feat note that this brings us closer to communicating information without needing a traditional signal, and that the ten miles they have reached could span the distance between the surface of the earth and space.
As we've explained before, "quantum teleportation" is quite different from how many people imagine teleportation to work. Rather than picking one thing up and placing it somewhere else, quantum teleportation involves entangling two things, like photons or ions, so their states are dependent on one another and each can be affected by the measurement of the other's state.
When one of the items is sent a distance away, entanglement ensures that changing the state of one causes the other to change as well, allowing the teleportation of quantum information, if not matter. However, the distance particles can be from each other has been limited so far to a number of meters.
Teleportation over distances of a few hundred meters has previously only been accomplished with the photons traveling in fiber channels to help preserve their state. In this particular experiment, researchers maximally entangled two photons using both spatial and polarization modes and sent the one with higher energy through a ten-mile-long free space channel. They found that the distant photon was still able to respond to changes in state of the photon they held onto even at this unprecedented distance.
However, the long-distance teleportation of a photon is only a small step towards developing applications for the procedure. While photons are good at transmitting information, they are not as good as ions at allowing manipulation, an advancement we'd need for encryption. Researchers were also able to maintain the fidelity of the long-distance teleportation at 89 percent— decent enough for information, but still dangerous for the whole-body human teleportation that we're all looking forward to.
Quote:Scientists have come a bit closer to achieving the "Star Trek" feat of teleportation. No one is galaxy-hopping, or even beaming people around, but for the first time, information has been teleported between two separate atoms across a distance of a meter — about a yard.
This is a significant milestone in a field known as quantum information processing, said Christopher Monroe of the Joint Quantum Institute at the University of Maryland, who led the effort.
Teleportation is one of nature's most mysterious forms 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 (a unit, or quantum, of electromagnetic radiation, such as light) 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 the JQI team, along with colleagues at the University of Michigan, has succeeded in teleporting a quantum state directly from one atom to another over a meter. 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 percent 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," Monroe said. "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 and entanglement
Physicist Richard Feynman is quoted as having said that "if you think you understand quantum mechanics, you don't understands quantum mechanics." Or sometimes he is cited thusly: "I think I can safely say that nobody understand quantum mechanics."
Nonetheless, here is how the University of Maryland describes Monroe's work.
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.
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.
Laser pulse initiates process
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 by the laser and falls back to one or the other of the two qubit ground states.
Depending on which one it falls into, the ion emits one of two kinds of photons of slightly different wavelengths (designated red and blue) that correspond to the two atomic qubit states. It is the relationship between those photons that will eventually provide the telltale signal that entanglement has occurred.
Beamsplitter encounter
Each emitted photon is captured by a lens, routed to a separate strand of fiber-optic cable, and carried to a 50-50 beamsplitter where it is equally probable for the photon to pass straight through the splitter or to be reflected. On either side of the beamsplitter are detectors that can record the arrival of a single photon.
Before it reaches the beamsplitter, each photon is in an unknowable superposition of states. After encountering the beamsplitter, however, each takes on specific characteristics.
As a result, for each pair of photons, four color combinations are possible — blue-blue, red-red, blue-red and red-blue — as well as one of two polarizations: horizontal or vertical. In nearly all of those variations, the photons either cancel each other out or both end up in the same detector. 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 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 also forces B into the 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 been written to ion A by the original microwave burst. Doing so results in the accurate teleportation of the information.
Teleportation vs. other communications
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 ... 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 work 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 the Joint Quantum Institute.
Too bad time travel will never happen, because if it did happen, then we would see time travelers from the future, but that obviously didn't happen yet, so it'll never happen.
Isn't the Earth or the sun or something supposed to die eventually? And we're supposed to all move into space colonies? If so, it'd be bad to travel into the past from then. If you do:
1. You either end up in space, and you can't go around pretending to be aliens entering Earth's orbit.
2. You go to where Earth was in the future, and travel back to when Earth was there. But then..Eh. I don't like that.
Corn Wrote:Too bad time travel will never happen, because if it did happen, then we would see time travelers from the future, but that obviously didn't happen yet, so it'll never happen.
If human kind finally gets the technology to travel through time, then they probably have the technology to easily cover up their tracks.
It's kind of the same argument with aliens. If they're thousands (maybe even millions) of years ahead of us; they should have the technology to be untraceable by our technology.
I've always wondered, if teleportation were to take you to the exact same point in the universe, but in another time, wouldn't it fail?
Say I travel to July of this year, I'd end up in space because the earth has moved around the sun to the other side of it.
Even more simple: I travel in time to 12 hours from now, I end up in the ocean because the earth rotated.
Darkmaniak Wrote:I've always wondered, if teleportation were to take you to the exact same point in the universe, but in another time, wouldn't it fail?
Say I travel to July of this year, I'd end up in space because the earth has moved around the sun to the other side of it.
Even more simple: I travel in time to 12 hours from now, I end up in the ocean because the earth rotated.
By the time we have tech to teleport people 100% of the time (or 99.99% of the time), then we should be able to pin point where we want to teleport people and from where we teleport people.
Corn Wrote:Too bad time travel will never happen, because if it did happen, then we would see time travelers from the future, but that obviously didn't happen yet, so it'll never happen.
I have always thought this!! if time travel where to exist, wouldnt we have seen time travelers already? but this also poses another question, maybe they just havent traveled to this time period yet...i say, scientist plant time capsles that should be opened when time travel exists, and leave a note in it that states that a time traveler should go to a certain date in the year the time capsel was made...yea...i know, there are many flaws in my plan, but hey, its worth a shot :/
I don't see how this theory would be feasible. No mass, gravity, or energy can occupy more than any one place in space-time. Yes space has the potential to be folded, compressed, expanded, and bent using spacial bubble compression and/or gravity wells, but you are still in one place at one time. Even if you were to freeze yourself down to Absolute Zero and remove yourself from the effects of time, you are still in the same place at the same time and time around you is still moving forward.
Time Travel is just not realistic and possible.
While you could build a transporter device from say a space station to the planet below, the closest possible actual method to do this would be spacial folding to open a wormhole between the station and the surface at which you would step off the space station to the planet surface or the opposite, but it would still be the same day at the same time.
LF> Explanation for time paradoxes. Until they explain things like "what happens if you travel to the past and kill yourself", time travel is impossible IMHO.
Also, what "past" and "future" really means, anyways? Where are our past actions "stored"? How can future exist if we didn't get there yet? What is present, if "now" is the future of "before" and the past of "after"? Etc...
Corn Wrote:Too bad time travel will never happen, because if it did happen, then we would see time travelers from the future, but that obviously didn't happen yet, so it'll never happen.
How would we even know if this turned out successful? Governments would probably keep this very hushed. Unless info on it gets leaked out on the internet. That is why I always hoped we would fail with time travel technology lmao. But at least it looks like we'll be making progress with quantum teleportation hopefully.
Very true. Technology like this would have to be kept extremely top secret. In the right hands it could be beneficial, but in the wrong hands, a complete road to ruin.
2011-01-20, 01:03 AM (This post was last modified: 2011-01-20, 02:24 AM by octopusprime.)
I'm so vested in time travel being impossible that if it becomes possible within my lifetime, i will travel back in time to erase time travel.
EDIT:
Hey guise, message from da future, time travel is not possible... anymore! BlTCHEZ
EDIT 2: It's a road to ruin no matter whose hands it is, good, bad, girlscout, someone who tries to erase timetravel, it doesnt matter in the end. biological zombie microwaves take over the future! destroy... the microwaves.
If time travel does exist, it would not really affect our timeline as the traveller would be in another dimension from ours and could cause as much wreckage as possible w/o affecting ours.
Corn Wrote:Too bad time travel will never happen, because if it did happen, then we would see time travelers from the future, but that obviously didn't happen yet, so it'll never happen.
Our dimension could be the "original one". The real present, the one extreme of the timeline where the future does not exist.
\took that out of my raccoon's brain hole. Obviously, I don't know anything about time travel science.
Do note the time travel spoken in the article is only on the direction past -> future. Doing the contrary I believe has been proven impossible by someone I don't remember.
You can always travel to the future by going at relativistic speeds anyway.
![[Image: 500x_time-travel.jpg]](http://cache.gawkerassets.com/assets/images/4/2011/01/500x_time-travel.jpg)
![[Image: Time%20teleportation.png]](http://www.technologyreview.com/blog/arxiv/files/50857/Time%20teleportation.png)
![[Image: time_machine.png]](http://imgs.xkcd.com/comics/time_machine.png)
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