SPOOKY ACTION: Quantum entanglement, famously dubbed "spooky action at a distance" by Albert Einstein, is harnessed in a new study to teleport quantum information from one ion to another.
Image: Library of Congress
-
Gravity's Engines
We’ve long understood black holes to be the points at which the universe as we know it comes to an end. Often billions of times more massive than the Sun, they...
Read More »
Quantum entanglement, whereby two or more objects are linked by an unseen connection, has some famously spooky effects. As quantum researcher Anton Zeilinger has said, entanglement can be thought of as a pair of dice that always land on the same number.
One of the most intriguing applications of this entanglement is quantum teleportation, in which the quantum state of a particle or atom is transferred to its entangled partner, even if they are separated physically. Such relaying of quantum information could form the backbone of long-distance quantum communication channels, but such a network remains far on the horizon.
A group of researchers, however, report today in Science that they've made headway in quantum teleportation, and thus communication. The team, led by physics graduate student Steven Olmschenk at the University of Maryland, College Park, succeeded in teleporting quantum information between ytterbium ions (charged atoms) three feet (one meter) apart.
Quantum teleportation has been demonstrated over macroscopic distances—hundreds of meters in at least one case—for photons, the fundamental particles of electromagnetic radiation, but ions are better candidates for quantum memory because they can store information for relatively long periods of time. (Christopher Monroe, a study co-author and the leader of the trapped-ion research group to which Olmschenk and several other co-authors belong, wrote about the potential for ions to serve as quantum bits, or qubits, in Scientific American last year.) The fundamental advantage of quantum information systems is that whereas a conventional digital bit can be 0 or 1, a qubit can be in a so-called superposition of 0 and 1 simultaneously.
Information is teleported from one ion to another by encoding quantum information onto the first ion. Once the ion is entangled with another, the state of each ion is indefinite until the first one is measured—an action that projects the other ion into one of two states. Conventional (nonquantum) communication channels relay information, gleaned from the first ion's measurement, as to which of those two states is correct, and a pulse of microwave energy sets the second ion into the state representing the information encoded on the first.
"We write information to the first ion, we perform this teleportation protocol, and it transfers the information over to the second ion," Olmschenk explains. He notes that this is the first teleportation experiment between two matter qubits that were a long distance apart.
Paul Kwiat, a physics professor at the University of Illinois at Urbana–Champaign, says that distant teleportation between potential qubits of quantum memory is a definite milestone. "The whole point of teleportation is getting the information far away," Kwiat says, noting that in prior micron-scale teleportation demonstrations with matter qubits, the researchers might have been better off simply moving the qubits physically from point to point. (A micron is one millionth of a meter, or about one twenty-five-thousandth of an inch.)
The ability to transmit information between bits of quantum memory could form the basis of so-called quantum repeaters, point-to-point networks that relay data down the line. "The idea is to in some sense boost the information along the way—to send it a short distance and then have it in some sense be amplified and sent on again and again to complete a transfer over a long distance," Olmschenk says.
Kwiat also sees this work finding applications in quantum communication as a link between quantum processors. But he would like to see the system boosted to higher operating speeds—in the current incarnation it takes an average of 12 minutes, or about 30 million attempts, to secure entanglement between a pair of ions.
Olmschenk agrees. "If you want to use this for real quantum communication purposes," he says, "we'd like it to go much faster." Toward that end, he says that small improvements in collecting and detecting the photons emitted by the ions, which are used to establish ion-to-ion entanglement, could provide a major boost in teleportation efficiency.
See what we're tweeting about
16 Comments
Add CommentFrom previous articles, I thought I understood that any information "transported" via quantum teleportation could not be unlocked until information about the original particle/ion was sent via more pedestrian means. If so, this work (while certainly interesting) doesn't really have any application to communications technology, right? Or am I missing something?
Reply | Report Abuse | Link to thisI wonder if this same technology could be used for other applications besides just communication. One example would be changing the temperature of different things. If one wanted to cool down a given atom, someone could ionize it, take a nearly identical ion with the desired temperature, then encode its quantum state and transmit that state to the desired ion using the method discussed in this article. If it worked, that would mean many other applications (possibly not limited to changing temperatures) would be possible as well.
Reply | Report Abuse | Link to thisWould this idea be possible with the current laws of thermodynamics. I am no expert on the subject, but heat is represented by thermal energy. If you could raise the thermal energy of one particle (via putting energy into the system), and that transfers (via quantum tleportation) to the other particle, then you have created energy, from nothing. If so, youve created a portable space heater!
Reply | Report Abuse | Link to thisAm I missing anything on that point, like I said, NOT an expert in this category.
Put another way, if the process involves a "conventional (nonquantum) communication channel" in addition to the quantum teleportation, you're certainly not gaining any speed. Perhaps the benefit of such quantum communication would be that the communication would be secure, since the conventional transmission would not contain the actual message...? But since both the conventional transmission and the entangled ion could be intercepted, I'm still not sure I understand what's exciting about this from a communications standpoint.
Reply | Report Abuse | Link to thisI find this article very unclear and indeed delusive. But in fact it says it: "Conventional (nonquantum) communication channels relay information". I'm not sure I understand the whole point of those experiences, but it is not instant teleportation (you cannot transmit information or matter faster than speed light).
Reply | Report Abuse | Link to this"(you cannot transmit information or matter faster than speed light)."
Reply | Report Abuse | Link to thisAs far as YOU know.
I've seen more than one article that suggests that we will indeed, in time, be able to make matter go faster than the speed of light by folding/compressing space...so there. It is never wise to tell Humankind what it cannot do.
I have been familiar with -- if not completely understanding of -- the idea of entanglement for some years. Even more so than the idea of a qubit (have you ever seen the math involved for quantum computing?)
Reply | Report Abuse | Link to thisTo Grasyop: I've read that it is faster than light -- instantaneous -- and it doesn't matter how far the entangled atoms/photons are separated. Even galaxies apart. That is the "spooky" part.
But the idea of one or MORE entanglements is intriguing. How many entanglements are possible? Does destroying one entanglemant destroy them all? If the thermal properties adressed by avocadoman333 and agenthucky were possible and a trillion entanglements could be produced that would be something.
Maybe I wasn't clear enough either. You can say, in a sense, that measuring an entangled particle transmits instantaneously information to the other particle. But you didn't *choose* the information which is transmitted and you could as well say that the information was already there before, non-locally. What you cannot do, in any sense, is transmit an information *you choose* faster than light. Nor matter. In other terms, you cannot communicate faster than light. This would be contrary to Einstein's theory, which remains unchallenged up to now. Articles suggesting that you can have faster than light communication are quack.
Reply | Report Abuse | Link to thisI'm not a physicist and english is not my first language, but I think I understand entanglement. And I agree with Tucker M's maybe more precise commentaries.
About thermal properties, as far as I know, the thermal property of a particle is simply its speed. Moreover, in this article, you're not copying information, just transfering it. And of course you cannot create energy from nothing.
OK. I've read this article twice now and what it sounds like they are doing is measuring the first ion, transmitting that information to the other person, who then uses a microwave burst to SET the second ion to the same value.
Reply | Report Abuse | Link to thisHow is this an example of quantum teleportation?
I think this article was badly written. There are ideas and quotes there that are confusing and contradictory.
Reply | Report Abuse | Link to thisWhat does the dice story have to contribute to communication/teleportation. Both dice start at the same spot. 2 different forces but the same result? That implies multiplication or predisposition of some sort.
This quote
"We write information to the first ion, we perform this teleportation protocol, and it transfers the information over to the second ion,"
makes me think that all you need to know is this quote
"the researchers might have been better off simply moving the qubits physically from point to point"
From what i understand, i detect this problem. The 2 ions have to be near in order to be entangled. So you COULD "teleport" the qubit to the other end of the galaxy instantly but FIRST you would have to somehow transfer the second ion there! That effectively cancels the "instant" thing.
Reply | Report Abuse | Link to thisFrom what i understand, i detect this problem. The 2 ions have to be near in order to be entangled. So you COULD "teleport" the qubit to the other end of the galaxy instantly but FIRST you would have to somehow transfer the second ion there! That effectively cancels the "instant" thing.
Reply | Report Abuse | Link to this"We write information to the first ion, we perform this teleportation protocol, and it transfers the information over to the second ion,"
Reply | Report Abuse | Link to thisExplain to me how "writing information" onto an entangled particle does not destroy the entanglement.
For example:
Let us say you have a particle that you split into two particles. You know that one is up-spin and the other is down-spin. You send one particle to your friend on the other side of the universe. Please explain how you can "change" the spin of the particle you have. You can't. All you can do is measure it. When you measure it, it automatically "causes" the other particle to have the opposite value. You haven't sent any information. However, both you and your friend know who has the up-spin and who has the down-spin. Nothing you do to the particle you have on hand will do anything to the other particle. If you could somehow 'change' its spin, you would simply be destroying the entanglement.
Please EXPLAIN how this works. All I ever read is smoke and mirrors about the transmission of quantum information.
Quantum entanglement. Seems like this is another bit of information which underscores the idea that the ancient idea of an "Aether," an all pervasive something, probably was correct.
Reply | Report Abuse | Link to thisInstantaneous transmission of information bits between indentical units of such a substance/substrate should be no surprise.
For an "Aether-Based Idea" which seems more and more likely to be valid, check http://groups.google.com/group/oscillatorsubstance.theory
no offense tucker but maybe you should drop trying to understand entanglement and stick to one night stands and partys. just kidding, by the way i like your book.
Reply | Report Abuse | Link to thisPerhaps not so spooky. Current physics allows for a grroup velocity and a phase wave velocity, the product it appers is just about always c^2. Clearly the speed of the phase wave velocity for a particle, must virtually always be greater than c. Perhaps that speed limit tend towards c^2. Which is very fast indeed to our measurement capabilities, enough for entanglement to appear instantaneous.
Reply | Report Abuse | Link to thisThe corolary is that we can expalin much of quntum phyiswcs this way and indeed much of energy equivalence. See: The formulation of harmonic quintessence and a fundamental energy equivalence equation. Physiscs Essays 23: 311-319.