Quantum information has been successfully teleported between two single atoms a metre apart

[Analog]

SYDNEY: Quantum information has been successfully teleported between two single atoms a metre apart ? a significant step towards long distance quantum communication and quantum computing, researchers say.

Quantum information is information about the physical state of a particle: its energy or spin, for example. Physicists in the U.S. have now managed to faithfully transfer this information between two atoms separated by a short distance, according to their study published today in the journal Science.

Quantum networks

"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," said Christopher Monroe, study author with the Joint Quantum Institute at the University of Maryland in College Park.

Before now, quantum teleportation had been achieved over very long distances with groups of atoms or with photons (see, Quantum communication breaks distance record), but this is the first time it has demonstrated with single atoms.

Only quantum teleportation between single atoms is a feasible way to hold and manage quantum information over long distances. "Photons are ideal for transferring information fast over long distances, whereas atoms offer a valuable medium for long-lived quantum memory," said Monroe.

In the study, the researchers put two ytterbium ions (A and B) in separate vacuum traps separated by one metre. Ion A was irradiated by microwaves, putting it into an unknown quantum state ? this state was the information to be transported.

Spooky action

The ions were excited by a laser pulse, which caused them to emit a single photon and returned to their initial state. The photons were measured in such a way that it was impossible to tell which ion emitted which photon. In the curious world of quantum mechanics, this projects an 'entangled' state onto the ions.

Entanglement is a bizarre phenomenon. It is a relationship between two particles such that an action undertaken on one particle ? such as a measurement of its quantum state ? affects the other particle, even if the two particles are far apart.

This is sometimes called 'spooky action at a distance' because there is nothing exchanged between the two particles, yet one can have an effect on the other.

http://www.cosmosmagazine.com/...ards-quantum-computing

 

[spidey07]

While impressive, I thought this was well known and explainable?

 

[Analog]

Originally posted by: spidey07
While impressive, I thought this was well known and explainable?

but this is the first time it has demonstrated with single atoms

 

[SlitheryDee]

Would this possibly mean faster than light communications are in our future or am I missing something.

 

[spidey07]

Originally posted by: Analog

Originally posted by: spidey07
While impressive, I thought this was well known and explainable?

but this is the first time it has demonstrated with single atoms

Well I'll make myself more clear - this has been well observed and I don't like the "nothing exchanged between the two particles" bit without going into further detail.

Just goes to show we have no freaking idea. But it is still fascinating. Makes the string crap gain strength.

 

[spidey07]

Originally posted by: SlitheryDee
Would this possibly mean faster than light communications are in our future or am I missing something.

That's kind of the whole idea. Space-time isn't really space-time and the forces aren't really forces.

 

[Flammable]

what does this do for us? society?

 

[schneiderguy]

Originally posted by: Flammable
what does this do for us? society?

It holds great promise for penis enlargement medications.

 

[SSSnail]

Holodeck.

 

[SlitheryDee]

Originally posted by: spidey07

Originally posted by: SlitheryDee
Would this possibly mean faster than light communications are in our future or am I missing something.

That's kind of the whole idea. Space-time isn't really space-time and the forces aren't really forces.

Friggin ansibles! Kickass.

 

[nakedfrog]

Originally posted by: Flammable
what does this do for us? society?

Right now, or eventually?

 

[techs]

So now I can reach my 250 Gb a month internet limit in like .000001 of a second.

 

[Born2bwire]

Originally posted by: SlitheryDee
Would this possibly mean faster than light communications are in our future or am I missing something.

No, these will not allow faster than light communications. What they are talking about in this article are entangling two atoms into a state, then they separate the atoms and by manipulating one (well both technically) of the atoms, they get back what the original state of the first atom was. The whole spooky action at a distance thing will not allow FTL communication. The primary reason being is that you cannot force the system into a desired state. The other reason is that entanglement generally requires close distances for it to occur, then you can bring one of the particles in the entangled system away and have them both remain entangled. So while the collapsing of the entangled state appears to be instantaneous (or at least FTL depending on how you play with simultaneity), you still have to physically move one of the particles at what has to be sublight speeds.

One of the reasons why this is useful is that for quantum computing or quantum networks, creating copies of a system's state is necessary. But whenever you take a measurement of the system, it collapses. One of the primary reasons for using quantum states is due to entanglement. For quantum computing, entanglement (or more accurately, superpositioning of states) allows for a problem to be processed in a parallel nature. For networks, entanglement ensures the security of a transmission. That is, on a quantum communication network, if someone snoops the quantum line and intercepts the message (or key), they will force a measurement and permanently alter the system (thus alerting the sender and receiver to the compromise). So the ability to create a copy of the system without forcing a measurement is a tricky problem. The scientists in this article state that they could use their system to create a quantum repeater that can help address these concerns.

 

[GodlessAstronomer]

Originally posted by: SlitheryDee
Would this possibly mean faster than light communications are in our future or am I missing something.

NO!

 

[GodlessAstronomer]

Originally posted by: spidey07

Originally posted by: SlitheryDee
Would this possibly mean faster than light communications are in our future or am I missing something.

That's kind of the whole idea. Space-time isn't really space-time and the forces aren't really forces.

No.

 

[imported_Devine]

Originally posted by: Born2bwire

Originally posted by: SlitheryDee
Would this possibly mean faster than light communications are in our future or am I missing something.

No, these will not allow faster than light communications. What they are talking about in this article are entangling two atoms into a state, then they separate the atoms and by manipulating one (well both technically) of the... head asplodes...

Back to Highly Technical where you belong demom, back I say!

 

[Random Variable]

But it still won't make my penis larger.

 

[Born2bwire]

Originally posted by: Devine

Originally posted by: Born2bwire

Originally posted by: SlitheryDee
Would this possibly mean faster than light communications are in our future or am I missing something.

No, these will not allow faster than light communications. What they are talking about in this article are entangling two atoms into a state, then they separate the atoms and by manipulating one (well both technically) of the... head asplodes...

Back to Highly Technical where you belong demom, back I say!

*whine* I was told there was free donuts and cookies here.

 

[Madwand1]

 

[SlitheryDee]

Originally posted by: Born2bwire

Originally posted by: SlitheryDee
Would this possibly mean faster than light communications are in our future or am I missing something.

No, these will not allow faster than light communications. What they are talking about in this article are entangling two atoms into a state, then they separate the atoms and by manipulating one (well both technically) of the atoms, they get back what the original state of the first atom was. The whole spooky action at a distance thing will not allow FTL communication. The primary reason being is that you cannot force the system into a desired state. The other reason is that entanglement generally requires close distances for it to occur, then you can bring one of the particles in the entangled system away and have them both remain entangled. So while the collapsing of the entangled state appears to be instantaneous (or at least FTL depending on how you play with simultaneity), you still have to physically move one of the particles at what has to be sublight speeds.

One of the reasons why this is useful is that for quantum computing or quantum networks, creating copies of a system's state is necessary. But whenever you take a measurement of the system, it collapses. One of the primary reasons for using quantum states is due to entanglement. For quantum computing, entanglement (or more accurately, superpositioning of states) allows for a problem to be processed in a parallel nature. For networks, entanglement ensures the security of a transmission. That is, on a quantum communication network, if someone snoops the quantum line and intercepts the message (or key), they will force a measurement and permanently alter the system (thus alerting the sender and receiver to the compromise). So the ability to create a copy of the system without forcing a measurement is a tricky problem. The scientists in this article state that they could use their system to create a quantum repeater that can help address these concerns.

Gah, I don't understand most of that. I expected one of the atoms to have to be carried manually to another location after they were entangled. After that, something can be learned about the atom that was left behind regardless of distance and at instantaneous speed, right? Ok, so the problem is that you have no control over what the state of the atom in question was to start with. You just know that you can learn that state from the other entangled atom, and therefore can do a nifty bit of quantum parlor magic but not transfer anything meaningful.

This quantum repeater IS meant to be a way to transfer information over large distances according to the article, although it seems to work nothing like what I was thinking about. I have one question then, Why bother with a repeater if the only signal being transmitted is the random state of a particle? How can what comes out the other end be useful if they haven't somehow coerced the particle in question into a desired state?

 

[Born2bwire]

Originally posted by: SlitheryDee

Originally posted by: Born2bwire

Originally posted by: SlitheryDee
Would this possibly mean faster than light communications are in our future or am I missing something.

No, these will not allow faster than light communications. What they are talking about in this article are entangling two atoms into a state, then they separate the atoms and by manipulating one (well both technically) of the atoms, they get back what the original state of the first atom was. The whole spooky action at a distance thing will not allow FTL communication. The primary reason being is that you cannot force the system into a desired state. The other reason is that entanglement generally requires close distances for it to occur, then you can bring one of the particles in the entangled system away and have them both remain entangled. So while the collapsing of the entangled state appears to be instantaneous (or at least FTL depending on how you play with simultaneity), you still have to physically move one of the particles at what has to be sublight speeds.

One of the reasons why this is useful is that for quantum computing or quantum networks, creating copies of a system's state is necessary. But whenever you take a measurement of the system, it collapses. One of the primary reasons for using quantum states is due to entanglement. For quantum computing, entanglement (or more accurately, superpositioning of states) allows for a problem to be processed in a parallel nature. For networks, entanglement ensures the security of a transmission. That is, on a quantum communication network, if someone snoops the quantum line and intercepts the message (or key), they will force a measurement and permanently alter the system (thus alerting the sender and receiver to the compromise). So the ability to create a copy of the system without forcing a measurement is a tricky problem. The scientists in this article state that they could use their system to create a quantum repeater that can help address these concerns.

Gah, I don't understand most of that. I expected one of the atoms to have to be carried manually to another location after they were entangled. After that, something can be learned about the atom that was left behind regardless of distance and at instantaneous speed, right? Ok, so the problem is that you have no control over what the state of the atom in question was to start with. You just know that you can learn that state from the other entangled atom, and therefore can do a nifty bit of quantum parlor magic but not transfer anything meaningful.

This quantum repeater IS meant to be a way to transfer information over large distances according to the article, although it seems to work nothing like what I was thinking about. I have one question then, Why bother with a repeater if the only signal being transmitted is the random state of a particle? How can what comes out the other end be useful if they haven't somehow coerced the particle in question into a desired state?

In regards to the first paragraph, exactly correct.

The naive idea would be that you create a bunch of entangled states and put each half of each entangled state in a box and send it out to your desired recipient. Then, the person at the other end would force each entangled state into a desired state, the receiver then would monitor the states and measure them (at a precise time to ensure that they have already been set) and then get a message out of the resulting states. This would be useful if your the sender and receiver have separated by a great distance. The problem is that we cannot force a specific state as the entangled state represents a superposition of possible states, there is no difference if atom A is up and atom B is down compared with A down and B up and thus you cannot fix one over the other. Einstein did not like this too much, hence the name "spooky action." He believed that the entangled states had some kind of hidden variable set at the beginning that predetermined the resulting states and created the EPR paradox to discuss this. Bell later came along and modified the EPR experiment and used it to show conclusively that there is no hidden variable.

The repeater is simply just to copy and retransmit the entangled system. In quantum cryptography, quantum states are used as a means for security. One process that I have read about in a paper is that you have two lines, the secure normal line to transmit the coded message, and the quantum line to transmit the necessary key information. A snooper could read both lines in a man-in-the-middle type of attack. Traditionally they could read the key info and retransmit it along as if nothing happened. This cannot happen unnoticed in a quantum line. The key is a random entangled state, but there is a correlation between the key that is read by the receiver and the resulting state left at the sender. If the snooper read the quantum line, he would collapse any entangled states, the key and sender included. So upon reading the key, he fixes the state at the sender and passes on a new entangled state to the reciever. The sender and reciever can then compare notes on the key and realize that it has been snooped by the discrepancy in the resulting states upon measurement. They would then know not to send out the coded message. The ability to find out whether or not the quantum line has been prematurely measured is the basis for that security. Now what happens if we need to transmit the state over such a great distance that the probability that it comes in correctly is too low? We would want to use a repeater, just like we do in optical networks and copper networks. But the repeater must transmit the entangled state, not a measurement of the state. That is why this is so useful because if we measured the state and retransmitted the measurement, then it would be no different than if the line was snooped.

A similar problem exists for quantum computing. It relies on the superposition of states and quantum entanglement. If you are processing a problem and want to store the state of the system, you need to be able to store the actual superposition and entangled states. A simple measurement would collapse the system into a single state and ruin the calculation.