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The First Universal Quantum Network

samzenpus posted more than 2 years ago | from the faster-than-fast dept.

Network 156

MrSeb writes "German scientists at the Max Planck Institute of Quantum Optics have created the first 'universal quantum network' that could be feasibly scaled up to become a quantum internet. So far their quantum network only spans two labs spaced 21 meters apart, but the scientists stress that longer distances and multiple nodes are possible. The network's construction is ingenious: Each node is represented by a single rubidium atom, trapped inside a reflective optical cavity. These atoms communicate with each other by emitting a single photon over an optical fiber. Each atom is a quantum bit — a qubit — and the polarization of the photon emitted carries the quantum state of the qubit. The receiving qubit absorbs the photon and takes on the quantum state of the transmitter. Voila: A network of qubits that can send, receive, and store quantum information. In another, probably more exciting test, the emitted photons were actually used to entangle the rubidium atoms."

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iPhone qubit? (-1)

Anonymous Coward | more than 2 years ago | (#39657417)

So when does the iPhone Qubit come out?

Re:iPhone qubit? (0)

Anonymous Coward | more than 2 years ago | (#39657471)

When stupid ACs stop posting lousy first posts.

Re:iPhone qubit? (4, Funny)

DynamoJoe (879038) | more than 2 years ago | (#39657645)

So "Never", then?

Re:iPhone qubit? (1)

ArcherB (796902) | more than 2 years ago | (#39658041)

So when does the iPhone Qubit come out?

As soon as Apple can patent the idea "for use on a handheld communications device", and it will be called the qBit. Actually, iQ is a much more catchy name.

Re:iPhone qubit? (2)

jamiesan (715069) | more than 2 years ago | (#39658709)

Archos is going to come out with one that has a 3 dimensional qbit array.

It will be 300 qbits long, 50 qbits wide, and 30qbits tall

I have no idea (3, Interesting)

Dyinobal (1427207) | more than 2 years ago | (#39657481)

I have no idea what any of that means! or what it's ultimate implications are technologically speaking but it sounds awesome!

Anyone care to enlighten me on the subject?

Re:I have no idea (3, Funny)

Anonymous Coward | more than 2 years ago | (#39657503)

It means that one day people will learn the difference between its and it's. Ah, to dream....

Re:I have no idea (1)

Anonymous Coward | more than 2 years ago | (#39658763)

Wow, its awesome!!

Re:I have no idea (3, Funny)

sycodon (149926) | more than 2 years ago | (#39657809)

Really, really fast porn downloads.

Re:I have no idea (3, Funny)

Anonymous Coward | more than 2 years ago | (#39658099)

But you'll have no way of telling whether a video is Goatse or not-Goatse until you watch it and collapse the state vector.

Re:I have no idea (1)

sycodon (149926) | more than 2 years ago | (#39658309)

Nice

Re:I have no idea (4, Funny)

Courageous (228506) | more than 2 years ago | (#39659359)

But you'll have no way of telling whether a video is Goatse or not-Goatse until you watch it and collapse the state vector.

Ah, Schrodinger's Goatse. Brought to you be the intersection of quantum mechanics and 4chan. Where physics and the dark, underbelly of the internet meet, even brave men fear to tread.

Re:I have no idea (5, Funny)

jd2112 (1535857) | more than 2 years ago | (#39658083)

It means that traceroute will be able to tell you response times or router addresses but not both.

Re:I have no idea (1)

fluffythedestroyer (2586259) | more than 2 years ago | (#39659951)

I have no idea what they mean too but to my understanding cause I didn't take any physics class (too busy screwing the girls back then). I think the "ultimate" goal or one of them is to create a zero latency network to any distance.

Entangled qubits might be able to form the basis of a quantum network with zero latency over any distance, which would make it rather useful for the intergalactic Galnet that will eventually succeed the internet.

Re:I have no idea (1)

onebeaumond (1230624) | more than 2 years ago | (#39660123)

Well, the researchers have managed to pass around a box containing a cat which is both dead and alive, if that helps any. This is just a prelude to the next step in their research. The next step will be to "special copy" a box, send one box off, then both parties look inside their boxes. If one box contains a dead cat, the other cat must be alive (copy entanglement rule). The idea is that a "man in the middle" would not be able to peek inside a box, because that ruins the box (another entanglement rule), and the other party would know it. Also, you would think that the live cat would need kitty litter whereas the dead cat doesn't, but apparently both boxes "smell" equally bad this way. Ok so you get the idea now, right? Answer yes if you're a liar.

Entanglement Confusion (2)

chiddy (2220596) | more than 2 years ago | (#39657485)

FTA: In theory, entangled qubits could be the basis of a quantum network with zero latency over any distance, which would make it rather useful for the intergalactic Galnet that will eventually succeed the internet. I'm pretty sure it's impossibly to transfer information faster than the speed of light http://en.wikipedia.org/wiki/No-communication_theorem [wikipedia.org]

Re:Entanglement Confusion (0)

Anonymous Coward | more than 2 years ago | (#39657609)

Aye, thanks -- have updated the story with a link to the no-communication theorem thingee.

Re:Entanglement Confusion (2)

SJHillman (1966756) | more than 2 years ago | (#39657631)

But without latency, what will the losing team blame it on?

Re:Entanglement Confusion (1)

DynamoJoe (879038) | more than 2 years ago | (#39657663)

aimbots.

Re:Entanglement Confusion (0)

Anonymous Coward | more than 2 years ago | (#39658145)

quantum aimbots

Here, FTFY.

They'll shoot in every possible direction at once and then destroy all universes where the bullet didn't hit.

Re:Entanglement Confusion (0)

Anonymous Coward | more than 2 years ago | (#39658645)

Wall hacks.

Re:Entanglement Confusion (2)

ByOhTek (1181381) | more than 2 years ago | (#39657973)

So...

Even faster troll first pots?

Nuts to that!

Re:Entanglement Confusion (1)

hobarrera (2008506) | more than 2 years ago | (#39658139)

When I read the title I got all exited thinking it would be just this: a quantum entanglement network :(

Call me when we have instant transfer of data (4, Interesting)

BenJeremy (181303) | more than 2 years ago | (#39657525)

I'll be impressed when they figure out how to harness entangled particles to achieve instant transfer of information over vast distances.

Imagine a world with no RF generated, yet completely connected. Better yet... imagine the entire solar system or beyond connected with such a network.

Re:Call me when we have instant transfer of data (0)

Anonymous Coward | more than 2 years ago | (#39657669)

What or who would we connect with? There's nothing out there, Space Nutter delusions notwithstanding.

Re:Call me when we have instant transfer of data (1)

tnk1 (899206) | more than 2 years ago | (#39658003)

We'd connect with ourselves, when we eventually leave the planet. Leaving the planet for permanent colonies is something I don't expect to see while I am alive, but it should be possible. Hell, it's probably possible now, but everyone seems to have higher priorities and there is no pressing need at the moment.

Still, I wouldn't argue with an even better communication method. In the end, better communications is a pillar of modern society as it allows more people to collaborate on much more complex projects.

Re:Call me when we have instant transfer of data (1)

sleigher (961421) | more than 2 years ago | (#39658799)

We'll get low on resources eventually. Then we will be out there looking for some. And I don't mean manufactured scarcity.

Re:Call me when we have instant transfer of data (1)

ByOhTek (1181381) | more than 2 years ago | (#39658047)

There's no proof that there is anything out there, but there's no proof their isn't either, and there's a lot of space for something else to develop. The idea that sentient life only developed on Earth in such a large universe requires belief in a spectacularly low-power god, IMO.

Of course, we'd have to transfer entangled nodes to these other civilizations, or have them transferred to us, which may not be feasible, ever, especially if sentience happens once or twice (or less) per galaxy.

However, if we manage, even by slowships, to colonize other star systems (not solar systems, there's only one solar system), then we'll be out there to communicate with.

Re:Call me when we have instant transfer of data (-1)

Anonymous Coward | more than 2 years ago | (#39657675)

The problem is that we would first have to find completely new physics to achieve that. Quantum mechanics does not allow faster-than-light communication. A simple mental model for quantum teleportation might be this: When you teleport a quantum state, it automatically gets encrypted with a classical one-time pad. However that classical key is provided to the sender. Therefore the sender has to transmit it to the receiver using classical communication so that the receiver is able to decrypt the teleported quantum state.

Re:Call me when we have instant transfer of data (0)

dullertap (1733776) | more than 2 years ago | (#39657755)

This comment is wrong. Imagine that the sender and receiver were sufficiently far apart, say a million light years. Quantum entanglement would allow them to have faster than light communication even if it was being "encrypted" and "decrypted" with a commodore 64.

Re:Call me when we have instant transfer of data (5, Informative)

Chris Burke (6130) | more than 2 years ago | (#39657859)

You're wrong. Quantum entanglement does not allow any information to be transferred faster than light.

Sitting a million miles away from your partner with your entangled particle, the only thing you know is that you and your distant partner will measure a correlated result from that particle -- a fact you already knew a million years ago when you parted company in your very-nearly-light-speed ship.

You do not know, and can not control, what the value will be. You do not know if the other person has measured their particle's state or not. Measuring the state destroys the entanglement. All you know after is that the result you got will be correlated with what they get, or got.

No information transfer is possible.

However entanglement is useful for other things. Like networks where you can detect if someone snooped on your packets.

Re:Call me when we have instant transfer of data (1)

dullertap (1733776) | more than 2 years ago | (#39657943)

I'm constantly measuring my particle. Spin up is zero. Spin down is one. How is this any different than, say, Morse code? Observing spin does not destroy entanglement. Quantum entanglement appears to propagate at thousands of times the speed of light.

Re:Call me when we have instant transfer of data (2)

Chris Burke (6130) | more than 2 years ago | (#39658265)

How is this any different than, say, Morse code?

In Morse Code you can control what state the wire is in without destroying it before a single bit is sent. In Morse Code you can measure the output of the wire without similarly destroying it.

Observing spin does not destroy entanglement.

No. Measuring spin causes the particle to take on a definite state, breaking the entanglement, as surely as measuring it's momentum.

Even if it didn't, though, you still couldn't communicate. You'd just know that a longer sequence of spin data you saw would be correlated with the other end. Interacting with the particle to change the spin would break the entanglement and they would not see a result correlated with the spin you gave the particle.

Re:Call me when we have instant transfer of data (1)

Anonymous Coward | more than 2 years ago | (#39658311)

I'm constantly measuring my particle. Spin up is zero. Spin down is one. How is this any different than, say, Morse code? Observing spin does not destroy entanglement. Quantum entanglement appears to propagate at thousands of times the speed of light.

For two reasons:

First, you're constantly measuring those values, but you can't force the particle to assume one of those values. So both you and the other person are reading random values. The same random values, yes, but random values nonetheless.

Second, reading the spin collapses it a (again, random) value. You might not destroy entanglement, but before you can "use" it again, both particles must be placed into a superposition state once more. Then you read it again. When you're doing the whole measuring / superposition dance, you don't know if you're the one who collapsed it or if you're reading the collapsed state the other person initiated it. Unless of course, you've agreed to always measure at previously established intervals, but you still can't get past the first problem. You'll both be reading the same random data, no information will be passed through.

Re:Call me when we have instant transfer of data (0)

Anonymous Coward | more than 2 years ago | (#39659725)

Why would you both be tampering with the same particle? You have two particles each, one send, one recieve. You have a 'handshake' that each of you sends via your respective 'sending' particles. Assuming your observations of your recieving particle match up with the handshake agreed upon between your parties, you can then begin decoding data from any future states sent (up until probably some form of termination signal), or begin your own handshake soon after so the other end can verify you're recieving their data, as well as begin signalling back your own data or a response.

Now whether this works in practice is another matter, but it doesn't seem a whole lot different than modern bidirectional communications.

Re:Call me when we have instant transfer of data (1)

Chris Burke (6130) | more than 2 years ago | (#39659873)

You have a 'handshake' that each of you sends via your respective 'sending' particles.

Sending anything at all is the problem. You can't.

Measuring or modifying your particle breaks the entanglement with the other. You can't control what the other person will see, you can't tell if they've checked. How then do you send your handshake?

Re:Call me when we have instant transfer of data (0)

Anonymous Coward | more than 2 years ago | (#39658071)

I think the bigger question then becomes, why does your very-nearly-light-speed ship take a year to travel a single mile?

Re:Call me when we have instant transfer of data (1)

Chris Burke (6130) | more than 2 years ago | (#39658359)

I think the bigger question then becomes, why does your very-nearly-light-speed ship take a year to travel a single mile?

It doesn't. The pit stops to refuel are really long though.

Re:Call me when we have instant transfer of data (3, Informative)

canajin56 (660655) | more than 2 years ago | (#39660183)

You do not know, and can not control, what the value will be. You do not know if the other person has measured their particle's state or not. Measuring the state destroys the entanglement. All you know after is that the result you got will be correlated with what they get, or got..

You forget that quantum shit be weird. If you think of particles as particles and their state as a 0/1 variable, then that's totally true. But particles do crazy things. One of the things they do is act like waves if nobody is looking. Entangled particles have to behave like the same sort of thing. In particular, if one of them enters a two slit setup and self interferes, the entangled pair has to also act like a wave and self interfere. This apparently occurs regardless of distance. What this means is that if Alice and Bob have a shared set of atoms. If Alice shoots an atom at a pair of slits, then Bob's atom will self interfere even if shot at an unshielded detector. Now that's not useful for sending messages, because statistically Bob can't tell if it hit where it hit because it's a particle, or because it's a wave. And the quantum equations say the same thing, that statistically the two states cannot be distinguished from random noise. However, the equations do not apply to larger systems, and we don't currently have ones that do.

Now, people assume there must be some quantum effect to prevent this from being used, because superluminal signals are mutually exclusive with causality, and most people assume causality holds. But there's no strong evidence either way at the moment.

Re:Call me when we have instant transfer of data (0)

Anonymous Coward | more than 2 years ago | (#39657893)

No it won't, because you can't send information that way.

'Entanglement' is merely a mathematical shorthand for 'that particle over there has always been in state X but you can't tell whether it's in state X or state Y until you measure the state of this particle over here'.

There's no actual information traveling anywhere.

Re:Call me when we have instant transfer of data (1)

janimal (172428) | more than 2 years ago | (#39658181)

Mod up. If this is correct, it's probably the most lucid explanation I have seen. Statements that "the theorem says so" amount to a faith argument, which doesn't convince me. But I'm no expert.

Re:Call me when we have instant transfer of data (1)

Anonymous Coward | more than 2 years ago | (#39658387)

Mod up. If this is correct, it's probably the most lucid explanation I have seen. Statements that "the theorem says so" amount to a faith argument, which doesn't convince me. But I'm no expert.

It's not correct. Bell's theorem proved that the Hidden variable theory [wikipedia.org] isn't true. The particle really does not have the state until you measure it.

That said, you still can't transfer information that way, because you can't force the particle to assume the state you want. If the particle can achieve state x or y, and you read x, you can be sure the other particle is in state y. However, you don't know if you're going to read x or y until you read it, so the only thing you can tell is that both you and other person are reading the same random data, containing no information.

Re:Call me when we have instant transfer of data (1)

LateArthurDent (1403947) | more than 2 years ago | (#39657947)

This comment is wrong. Imagine that the sender and receiver were sufficiently far apart, say a million light years. Quantum entanglement would allow them to have faster than light communication even if it was being "encrypted" and "decrypted" with a commodore 64.

No, it does not. Another poster already linked to the No-Communication theorem [wikipedia.org] . Basically, the effects of quantum entanglement are transmitted faster-than-light, instantaneously, in fact. Information through this process cannot be transferred faster than light.

It boils down to this: if you're light-years apart from me, and we each have one particle that is entangled with the other, if I collapse the state of my particle, I know which state your particle has collapsed to simultaneously. However, I cannot force my particle to collapse to a particular state, so I can't force it to send you any information. I can't even send you the information that I have collapsed the state of my particle. Measuring its state collapses it, and you won't know if your particle has collapsed to a state or not unless you measure it.

Re:Call me when we have instant transfer of data (1)

Nemyst (1383049) | more than 2 years ago | (#39657677)

Sorry, not gonna happen. You might as well unplug the phone if that's the call you're waiting for.

Violating relativity is not on anybody's todo list; entanglement has many useful properties, but you still can't break the speed of light barrier with it, and that isn't an implementation issue.

Re:Call me when we have instant transfer of data (-1, Redundant)

dullertap (1733776) | more than 2 years ago | (#39657725)

Uh, yes you can. Entanglement is order of magnitude faster than the speed of light. It has nothing to with light however. Experiments have been done to see how "fast" it is.

Re:Call me when we have instant transfer of data (1)

Anonymous Coward | more than 2 years ago | (#39657857)

Yes, the "effects" of entanglement occur faster than the speed of light, but this cannot be used to transfer information in any way (this is a mathematically proven consequence of the principles of QM), so FTL communication is still physically impossible in a quantum universe.

Re:Call me when we have instant transfer of data (0)

Anonymous Coward | more than 2 years ago | (#39657861)

Repeating yourself doesn't make it any more true. If I cared to log in, I'd search for my "-1, Has Never Read Anything About Transmission of Information via Quantum Entanglement Or Understands How It Works" mod button.

Seriously, Wikipedia for J.S. Bell's theorem, dude, before you blow a gasket.

Re:Call me when we have instant transfer of data (3, Informative)

tnk1 (899206) | more than 2 years ago | (#39658107)

Yes, but entanglement cannot violate causality, which is basically what would happen if you transmit information faster than the speed of light. That means that entanglement itself *could* be faster than light, but it has to have some property that mangles any information you try to piggy back on the process so that it is useless as a communication source at FTL speeds.

The problem isn't getting something faster than light, it's being able to make any use of the process to transmit information.

Re:Call me when we have instant transfer of data (1)

sexconker (1179573) | more than 2 years ago | (#39659797)

Uh, yes you can. Entanglement is order of magnitude faster than the speed of light. It has nothing to with light however. Experiments have been done to see how "fast" it is.

Stop posting this bullshit. Information cannot travel faster than the speed of light. Entanglement does not get around this.

Re:Call me when we have instant transfer of data (0)

Anonymous Coward | more than 2 years ago | (#39657713)

What you are referring to is by all established theories completely impossible. entanglement can at most deliver instant correlation, but this cannot be used to transmit information. We are limited by the universal cap which is the speed of light.

Re:Call me when we have instant transfer of data (1)

bigtrike (904535) | more than 2 years ago | (#39657721)

"instant" meaning at the speed of light? It's theoretically impossible to transfer information any faster than that.

Re:Call me when we have instant transfer of data (1)

RivenAleem (1590553) | more than 2 years ago | (#39657843)

I thought the rule was anything containing mass could be accelerated past the speed of light. The whole point of entangled atoms, was that the state of one atom was changed, the state of the entangled pair changed to match, and that this change was instantaneous. If the 2 atoms could be moved lightyears apart then you could have (even if it's primitive Morse code) instant transfer of information. Because the information has no mass, you are not breaking the light barrier.

That's the basis of the Ansible [wikipedia.org] in Ender's Game (and others)

That's the Sci-Fi version. In this experiment the 'entanglement' was caused by a photon emitted by one atom, down a fiber line to the other atom. So one could argue that it's not classical entanglement, and that the transfer of information between the atom pair is still limited by the speed of the photon (light).

Re:Call me when we have instant transfer of data (1)

bigtrike (904535) | more than 2 years ago | (#39658585)

IIRC, anything with mass can be accelerated to the speed of light with an infinite amount of energy. Anything without mass has a maximum speed of the speed of light.

Re:Call me when we have instant transfer of data (1)

Lumpy (12016) | more than 2 years ago | (#39658267)

Define speed of light.

If you are measuring a distance in 3D space and the time it takes? yes.

If quantum entanglement exists in 5,6 or even 7D space, the entanglement distance may not be anywhere as far as the 3D space distance.

Therefore it IS possible in relation to the observer and based on 3D space constraints to transmit information faster than the speed of light without violating Causality.

Re:Call me when we have instant transfer of data (1)

sexconker (1179573) | more than 2 years ago | (#39659913)

Define speed of light.

If you are measuring a distance in 3D space and the time it takes? yes.

If quantum entanglement exists in 5,6 or even 7D space, the entanglement distance may not be anywhere as far as the 3D space distance.

Therefore it IS possible in relation to the observer and based on 3D space constraints to transmit information faster than the speed of light without violating Causality.

Wow you're dumb.

Imagine a 2D plane. Imagine 2 points, A and B, on that plane. They are X units apart.
Find a path from A to B whose length is shorter than X. Feel free to use as many dimensions as you want.

Furthermore, there is exactly zero evidence that more than 3 spatial dimensions exist.

Re:Call me when we have instant transfer of data (1)

ceoyoyo (59147) | more than 2 years ago | (#39657883)

Why not just imagine instant, and free, teleportation? Both violate the lawsof physics as we know them.

Quantum Internet (4, Interesting)

pablo_max (626328) | more than 2 years ago | (#39657555)

I am no physicist, so I am actually asking seriously to those of you who are.
As it is already know, particles which are entangled at the quantum level have an instant and equal reaction on one another regardless of distance. Would it not be possible to use this "Quantum Internet" for C from say, a satellite controller a rover on Mars and one on Earth?
I have heard that it is not really workable, but is that from an engineering prospective or from a laws of physics perspective?

Re:Quantum Internet (0)

Anonymous Coward | more than 2 years ago | (#39657799)

I am also not a physicist, but I am a mathematician with some basic familiarity with quantum computing (from a computer science perspective). From what I understand, it is impossible to use entanglement to send or receive any information at all - no matter how many entangled particles you have arranged you cannot transmit a single bit/qubit through them. However, you can use entanglement along with transmission of classical information to send more interesting information - quantum teleportation is the transmission of a single qubit via an existing entangled pair of qubits and the transmission of two bits of classical data. Arguably (depending on which interpretation of QM we accept) a qubit contains more information than two bits of classical data, but that information is fundamentally inaccessible.

Re:Quantum Internet (1)

pablo_max (626328) | more than 2 years ago | (#39657871)

Right, but you are not actually sending data. When they are entangled, you separate them. When you change the state of one, it changes the state of another. Why could you not just view the state as a way of transferring information?

Re:Quantum Internet (4, Informative)

Chris Burke (6130) | more than 2 years ago | (#39658039)

When you change the state of one, it changes the state of another. Why could you not just view the state as a way of transferring information?

Because you can't control the state that it collapses to when you measure it and break the entanglement. You can't tell whether or not the person on the other end has already done this. All you know is that whatever state you measure, they will see a correlated result. Which you already knew; you've learned nothing.

A useful analogy* -- it's like you and the person you want to "communicate" with put two marbles, one red and one black, into two bags. You randomly pick one, your partner takes the other. You fly apart at 0.9c for a while. Then you look in your bag. It's a red marble. You now "instantly" know that your partner has a black marble -- but you haven't actually communicated anything.

* It's just an analogy; the fact that it doesn't obey Bell's theorem is immaterial to understanding why you haven't communicated anything.

Re:Quantum Internet (1)

Endovior (2450520) | more than 2 years ago | (#39658207)

Speaking as someone who actually knows a bit about the science; this really is a very good analogy. I would add that basically all the work done to date doesn't actually have anything to do with getting useful information transfer from looking at the marbles (which is still actually impossible, under current theories), it's more preventing the marbles from falling into random buckets of paint (ie: getting their state changed by various environmental factors), and providing less then no information.

Re:Quantum Internet (1)

Chris Burke (6130) | more than 2 years ago | (#39658941)

Speaking as someone who actually knows a bit about the science; this really is a very good analogy.

Thanks! I added the disclaimer because I've had people complain that because the outcome of the marble-bag experiment doesn't precisely match the statistical behavior of quantum particles it is a bad analogy. But... that's not what the analogy is about. :)

it's more preventing the marbles from falling into random buckets of paint (ie: getting their state changed by various environmental factors), and providing less then no information.

Isn't this part of the appeal of the quantum network -- if environmental factors like a dude sniffing your packets broke the entanglement, you could detect it? I guess if you can't prevent the environment from breaking entanglement all the time then that's a problem. :) Are there other applications for this known?

Re:Quantum Internet (0)

Anonymous Coward | more than 2 years ago | (#39659073)

If you want to add a disclaimer, then add the right one. The analogy is different from quantum entanglement because it *obeys* Bell's theorem instead of violating it.

Re:Quantum Internet (1)

Chris Burke (6130) | more than 2 years ago | (#39659325)

But if I didn't fuck up, how would I be able to keep striving to improve?

Yeah... I'm not buying it either...

Re:Quantum Internet (1)

Courageous (228506) | more than 2 years ago | (#39659775)

(which is still actually impossible, under current theories)

This may seem like a trivial, idle remark, but I sincerely appreciate the effort you made in saying "impossible, under current theories." There are too many peoplewho fall into either the linguistic or mental trap of treating current theory as the ground truth state of the universe.

C//

Re:Quantum Internet (1)

Asic Eng (193332) | more than 2 years ago | (#39658367)

So is there anything you could actually accomplish with this "network"? I assume you are correct, which would then make the article complete hogwash.

Re:Quantum Internet (2)

Chris Burke (6130) | more than 2 years ago | (#39658891)

So is there anything you could actually accomplish with this "network"?

Yes! Because measuring the state of the particles breaks the entanglement, in a quantum network you would theoretically be able to tell if someone was listening in -- you'd send the correlation information along with the regular data, and if it didn't line up with what you saw in your particles at your end, then you'd know that the entanglement had been broken and someone had sniffed your packets.

The application would be key exchange. You could just send a shared key over the insecure network, and if nobody intercepted it, then you're good to go.

This is how I understand it, anyway.

The article is indeed wrong about the "zero latency" aspect. If the researchers were actually claiming to be able to send information instantaneously then they'd be a lot more obvious about it -- see the recent ICARUS FTL neutrino result where the mere hint of FTL communication resulted in international attention and a constant barrage of headlines.

Re:Quantum Internet (1)

micahraleigh (2600457) | more than 2 years ago | (#39659659)

What if you had a bag of entangled particles? Both sides have a bag of say 10,000 serialized, entangled particles and the guy holding the bag in DC asks, "Have they launched anything yet?" "No." "Okay, checking the next particle. Have they launched anything yet?" "No." Etc.

Re:Quantum Internet (1)

Chris Burke (6130) | more than 2 years ago | (#39659767)

Both sides have a bag of say 10,000 serialized, entangled particles and the guy holding the bag in DC asks, "Have they launched anything yet?" "No."

But how are you determining that the answer to the question is "no"? You don't know if they've measured their particles or not. You only know that when you measure yours, you'll see a result that's correlated with what they see.

Re:Quantum Internet (0)

Anonymous Coward | more than 2 years ago | (#39657855)

It's from a law of physics perspective. Without additional classical information sent along, when using entanglement for communication, all you get from your quantum system alone is white noise. Only with the additional classical information (which by itself also looks like white noise) you can get any information. And that classical information transfer is still bound by the speed of light. Great for cryptography (basically you non-locally create a one-time pad), useless for faster-than-light communication.

Re:Quantum Internet (1)

Anonymous Coward | more than 2 years ago | (#39657899)

Suppose you have a rover on Mars and a rover on Earth, and the question is whether they should go North or South. With quantum entanglement, you can say "go the same way!" and both rovers will instantly go the same way, or you can say "go different ways!" and both rovers will instantly go different ways. But when you do this you can't control which way a particular rover is going, which will be random. You only control the "xor" of the two directions.

Re:Quantum Internet (0)

Anonymous Coward | more than 2 years ago | (#39659055)

but why can't a change in direction or a controlled pattern of changes in direction indicate anything? When the person notices a change in direction, who cares if the rovers are traveling in the same direction or in opposite directions, the person on the other end can just notice the timing of that change.

For it to prevent communication using your analogy the following would have to be true. The quantum system would have to automatically signal changes in direction at random, some being in the same direction and others being in the opposite direction, without any human input. Then, to prevent us from noticing controlled patterns in timing, when I signal that the rovers should travel either in the same or opposite directions, the quantum system would have to set a random delay between when I set it and when it actually executes my setting, that random delay being equal to whatever its next random state alteration time would be had I not signaled anything. and, of course, such a random delay makes such signals not instant, though perhaps easily faster than light.

Anything different can lead to communication because we can communicate timing patterns in the form of directional changes, even in the face of some random noise (ie: random directional changes).

Re:Quantum Internet (1)

tnk1 (899206) | more than 2 years ago | (#39658451)

The problem with using this for FTL is what is known as the no-communication theorem. The quantum state of two entangled particles will change faster than light (instantly, actually), but you will never be able to control what state that the particle switches to when you make the change because of the way quantum mechanics works.

For instance, I separate two entangled particles and then proceed to start altering the state of one of them. I know I can change the state, but I do not know what the value of that new state will be until I observe it.

Also, the state of the particles is always uncertain until observed, and can change between observations, so one observation does not fix the quantum state of the particle pair permanently.

When I do change the state purposely on one side, quantum entanglement means that the state on the other particle will change at the same time to be the exact same value, as expected. However, since I was unable to predict what state the particle will be in when it is changed, the other side cannot tell if the change was due to transmission or just some random event. Thus, your message arrives faster than light, but no one can read it, or even realize that there even was a message sent to begin with.

That was my paraphrase of it. I'm sure someone could do better, but the central point is the same. Having an FTL particle or process does not mean you can do anything useful with it..

Re:Quantum Internet (1)

atisss (1661313) | more than 2 years ago | (#39659799)

However, since I was unable to predict what state the particle will be in when it is changed, the other side cannot tell if the change was due to transmission or just some random event. Thus, your message arrives faster than light, but no one can read it, or even realize that there even was a message sent to begin with.

If the state changes are truly random, you can work by detecting non-random anomalies in state, and build an information transmission scheme around it.

Re:Quantum Internet (1)

FridayBob (619244) | more than 2 years ago | (#39659081)

... particles which are entangled at the quantum level have an instant and equal reaction on one another regardless of distance. Would it not be possible to use this "Quantum Internet" for C from say, a satellite controller a rover on Mars and one on Earth? ...

It would be cool, but a quick search shows that the answer is apparently No. It seems two entangled atoms are like two coins that mirror each other such that if one is tossed, the next time the other is tossed it will show the same value. It's weird, but it can't be used for communication, something that also prevents causality from being violated.

Re:Quantum Internet (1)

Strilanc (1077197) | more than 2 years ago | (#39659845)

Entanglement allows you to instantaneously share a bit of information, but doesn't let you control what the bit will be. This makes it useless for most communication tasks.

That being said, entanglement can allow coordination in a way that is similar to communication. Check out the Wikipedia article on "quantum pseudo telepathy".

Heisenberg Disagrees? (2)

dullertap (1733776) | more than 2 years ago | (#39657635)

Doesn't the Heisenberg Uncertainty principle kind of say that when these machines are determining spins of particles, that they cause them to change? ie entropy?

99.8% data loss (2)

melonman (608440) | more than 2 years ago | (#39657707)

From TFA, this is apparently a huge improvement on previous attempts, but it's still not exactly dazzling. What sort of self-correcting protocol do you need to handle 499 of every 500 bits being lost?

Re:99.8% data loss (1)

PIBM (588930) | more than 2 years ago | (#39657913)

Sending 500 times the exact same information would fix your specific problem... =)

Re:99.8% data loss (0)

Anonymous Coward | more than 2 years ago | (#39657917)

Quantum parity error correction.

arxiv.org/pdf/1007.1778

Re:99.8% data loss (2)

Luyseyal (3154) | more than 2 years ago | (#39659809)

I guess we won't discuss the state-of-the-art in neutrino communication, then...

http://www.technologyreview.com/blog/arxiv/27648/ [technologyreview.com]

These guys used an experiment called NuMI (NeUtrino beam at the Main Injector) to generate an intense beam of neutrinos. The beam consisted of about 25 pulses each separated by 2 seconds or so, with each pulse containing some 10^13 neutrinos.

The beam is pointed at a detector called MINERvA weighing about 170 tonnes and sitting in an underground cavern about a kilometre away. To reach MINERvA, the beam has to travel through 240 metres of solid rock.

MINERvA is one of world's most sensitive neutrino detectors and yet, out of 10^13 neutrinos in each pulse, it detects only about 0.8 of them on average.

Nevertheless, that's enough to send a message. The FermiLab team used a simple on-off protocol to represent the 0s and 1s of digital code and transmitted the word "neutrino".

The entire message took about 140 minutes to send at a data rate that these guys later worked out to be about 0.1 bits per second with an error rate of less than 1 per cent.

-l

"carries the quantum state"? (3, Informative)

fatphil (181876) | more than 2 years ago | (#39657745)

You can't copy quantum state. The only way it can carries the quantum state of something is if it also destroys that something's quantum state. (But of course you can't destroy quantum state either, you've effectively just swapping quantum state.)

So information might be passed around, but it's never actually being shared.
Which isn't much of a network.

Disclaimer - I'm rusty.

Re:"carries the quantum state"? (0)

Anonymous Coward | more than 2 years ago | (#39657995)

Since when does "network" imply "sharing"? Note that despite the fact that classical information can be duplicated at will, the typical internet packet still is transported from one sender to one receiver. Shall I conclude that the internet is not a network? And what about the water supply network? Last I checked, you could not send the same drop of water to different houses.

Re:"carries the quantum state"? (0)

Anonymous Coward | more than 2 years ago | (#39658327)

As a computer programmer, this concept of not being able to transmit something with entanglement has always seemed like a fallacy to me. In my mind there has to be a way to pull it off. Unfortunately, a lot of physicists aren't programmers so they're just looking at the raw data and saying it can't be done, but they're not thinking like a software engineer and saying how can we at least get this to halfway work.

I'll throw out an idea, and I'm not sure if it's physically possible. Okay, so as soon as you observe the spin of an atom, you've changed the atom which means that the sender never knows what he actually sent to the destination. He sent something, but he doesn't know what it is. So, here is my question, is there a way to simultaneously send the same unknown data to two destinations instead of one? A duplicate of the same unknown state being sent to two different destinations, with the sender themselves not being aware of what was sent. If so, the sender themselves could be on the receiving end of one of those two signals and use that to determine what was sent to the actual destination.

Did I just solve something?

Re:"carries the quantum state"? (1)

GameboyRMH (1153867) | more than 2 years ago | (#39658605)

I don't think so. Assuming that's all possible, how does that help the sender to send meaningful information? All he knows is that he just sent a 1 or a 0. He doesn't know what the next bit will be. It's still no better than having two magically-FTL-interlinked RNGs.

Scaling Up (1)

bacon.frankfurter (2584789) | more than 2 years ago | (#39657771)

Sounds like it's going to be a pretty gigantic leap to go from this experiment to an entire Internet. Keeping in mind that they only sent, received, and stored one bit, from one persistent store to another, each of which was capable of store who knows how many bits.

One bit.

How many bits (not bytes, bits) make up an "internet"?

+1 internets to anybody who can give a reasonable answer.

Re:Scaling Up (1)

the_pace (1319317) | more than 2 years ago | (#39657863)

On top of that, 99.8% failure rate. We are looking at quite a long time before quantum network becomes even close to useful.

Re:Scaling Up (1)

niftydude (1745144) | more than 2 years ago | (#39657901)

How many bits (not bytes, bits) make up an "internet"?

Why, eight times the number of bytes of course. Did I win teh internets?

Installer's dream (1)

rullywowr (1831632) | more than 2 years ago | (#39657865)

"Hey Bart, pass me another 500ft spool of that rubidium!"

Re:Installer's dream (1)

Anonymous Coward | more than 2 years ago | (#39657981)

That's nothing. I used to have a Quantum hard drive.

IP Traffic into the future (1)

Big Hairy Ian (1155547) | more than 2 years ago | (#39657895)

So basically we could have one of these nodes orbiting Mars and communicate with it instantaneously when actually the node orbiting Mars is 18 minutes or more ago but it could communicate to our past the same way..... Oh dear my head just exploded!

quantum what??? (2)

stanlyb (1839382) | more than 2 years ago | (#39657983)

If this is really a quantum network, why do they need a fiber to send the information!!!!!!!!!!!!!

mod Up (-1, Offtopic)

Anonymous Coward | more than 2 years ago | (#39658009)

users. Surprise

I'm looking forward (1)

aglider (2435074) | more than 2 years ago | (#39658057)

to read the quantum version of Slashdot.

Ansible? (1)

mspring (126862) | more than 2 years ago | (#39658177)

Still no ansible [wikipedia.org] I guess.

I'm In the Wrong Field (1)

fearofcarpet (654438) | more than 2 years ago | (#39658339)

Ritter acknowledges that the new work is simply a prototype, and one for which numerous improvements are possible. For instance, the transfer of a quantum state between labs succeeded only 0.2 percent of the time, owing to various inefficiencies and technical limitations. "Everything is at the edge of what can be done," he says. "All these characteristics are good enough to do what we've done, but there are clear strategies to pursue to make them even better."

I wish I could publish a 0.2 % yield, or an experiment that worked 0.2 % of the time in Nature! Clearly I'm in the wrong field (but in all serious, getting atoms to communicate through a fiber optic cable is pretty freaking cool.)

Re:I'm In the Wrong Field (1)

GameboyRMH (1153867) | more than 2 years ago | (#39658655)

Hey as long as it can be made to work reliably it's still a link, not unlike a range-limit wifi connection with a ton of dropped packets.

China's Muppet Communique (0)

Anonymous Coward | more than 2 years ago | (#39658461)

China is not amused
April Fool's joke:
http://qbnets.wordpress.com/2012/04/01/chinas-muppet-communique/

FTL info transfer. (1)

kaws (2589929) | more than 2 years ago | (#39658465)

I was under the impression that no interactions of QM go FTL. But a lot of posts have been saying that collapse is basically instantaneously. If this is the case than a encumbersome form of FTL communication could be made. Instead of measuring the states, just use positioning. Like optimise the signal so that you can send your message in a byte, then arrange it so each molecule is arranged like a normal binary number of 1s and 0s. Then send a message by just collapsing the corresponding bits. I suppose that this would only work for emergency messages considering reestablishment the entanglement would be a lot slower.
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