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Theorists Make Quantum Communications Breakthrough

kdawson posted more than 6 years ago | from the shannon's-cat dept.

Communications 155

KentuckyFC writes "One of the cornerstones of modern physics is Claude Shannon's theory of communication, which he published in 1948. If you've ever made a phone call, watched TV, or used a computer, you've got Shannon to thank for describing how information can be moved from one place in the universe to another using an idea called the channel capacity. But nobody has been able to develop a quantum version of this theory. So physicists have no idea how much quantum information can be sent from one point to another. Now two American physicists have made an important breakthrough by proving that two quantum channels with zero capacity can carry information when used together. That's interesting because it indicates that physicists may have been barking up the wrong tree with this problem: it implies that the quantum capacity of a channel does not uniquely specify its ability for transmitting quantum information (abstract). And that could be the idea that breaks the logjam in this area."

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Don't forget... (-1, Troll)

Anonymous Coward | more than 6 years ago | (#24491023)

To pay your $699USD licensing fee you cock smoking teabaggers!

Channel theory link broken (4, Insightful)

Sentry21 (8183) | more than 6 years ago | (#24491027)

Re:Channel theory link broken (1)

LostCluster (625375) | more than 6 years ago | (#24491213)

And that link appears broken... slashdotted.

Re:Channel theory link broken (5, Funny)

Anonymous Coward | more than 6 years ago | (#24491593)

You fools! You've gone and changed the article by clicking the link.

Re:Channel theory link broken (4, Funny)

SEWilco (27983) | more than 6 years ago | (#24491695)

Observers have indeed changed the state of the target to dead.

Re:Channel theory link broken (1, Funny)

Anonymous Coward | more than 6 years ago | (#24492485)

Observers have indeed changed the state of the target to dead.

Odd.....I just looked and it was alive......

Re:Channel theory link broken (5, Funny)

vyruss000 (525644) | more than 6 years ago | (#24492519)

Links in Slashdot are simultaneously dead and alive! Clicking on them decides which ;)

Re:Channel theory link broken (2, Funny)

n3tcat (664243) | more than 6 years ago | (#24493307)

I'm going to name my next cat "TFA" and then I can say he "slashdotted the couch"

Re:Channel theory link broken (0)

Anonymous Coward | more than 6 years ago | (#24491827)

Sory was to moderate you +1 funny. Misclicked...
This post hopefully saved me...

Re:Channel theory link broken (2, Insightful)

Anonymous Coward | more than 6 years ago | (#24491849)

Oh, It did...
Anyone seen my cat?
Wanted dead and alive.

Re:Channel theory link broken (1, Funny)

Anonymous Coward | more than 6 years ago | (#24492037)

Mod parent plus and minus one!

Re:Channel theory link broken (1)

Migity (1199059) | more than 6 years ago | (#24492571)

Already took care of that. Isn't that what you're seeing?

So 0+0=1! (5, Funny)

Anonymous Coward | more than 6 years ago | (#24491043)

Now two American physicists have made an important breakthrough by proving that two quantum channels with zero capacity can carry information when used together.

So who wants to join my class-action lawsuit against math teachers?

Re:So 0+0=1! (5, Funny)

z0idberg (888892) | more than 6 years ago | (#24491633)

I do!

That makes three of us!

Re:So 0+0=1! (2, Funny)

petraska (1132643) | more than 6 years ago | (#24491823)

And remember, 2+2=5 for very large values of 2.

Re:So 0+0=1! (1)

Cheesebisquit (1324407) | more than 6 years ago | (#24491857)

I got this joke about 5 minutes after I read this.

Re:So 0+0=1! (1)

Thyrteen (1084963) | more than 6 years ago | (#24491935)

5: Informative? Man, apparently these communication inconsistencies apply to the mod system too.. Go ahead, vote me offtopic. Let's see what it turns up as.

Re:So 0+0=1! (1, Insightful)

Anonymous Coward | more than 6 years ago | (#24492001)

I believe some mods will mod a particularly funny post as something else positive as Funny mods dont go towards the posters Karma rating.

(Now watch this get modded something crazy).

Re:So 0+0=1! (1)

LittleBigLui (304739) | more than 6 years ago | (#24493309)

cool, now i'm the pope!

how can we stand for this? (-1, Troll)

Anonymous Coward | more than 6 years ago | (#24491057)

faggots eat shit out of each others asses. why do we let this go on unchecked? they're a drain on society.

Re:how can we stand for this? (0)

Anonymous Coward | more than 6 years ago | (#24492365)

recycling.... duh.

quantum mechanics (5, Interesting)

edwebdev (1304531) | more than 6 years ago | (#24491059)

"two quantum channels with zero capacity can carry information"
Feynman once said that nobody understands quantum mechanics, and this is why.

Re:quantum mechanics (0)

topham (32406) | more than 6 years ago | (#24491423)

Conversely if two physicists walk into a bar, how many patrons have lives?

Answer: The same number as there were before they entered.

Re:quantum mechanics (4, Informative)

Colonel Korn (1258968) | more than 6 years ago | (#24491597)

Conversely if two physicists walk into a bar, how many patrons have lives?

Answer: The same number as there were before they entered.

In my experience physicists are generally rather cool, worldly people who have well developed personal lives.

Re:quantum mechanics (5, Funny)

Anonymous Coward | more than 6 years ago | (#24491629)

PHYSICIST!

you outed yourself!

Re:quantum mechanics (0)

Anonymous Coward | more than 6 years ago | (#24492051)

In my experience physicists are generally rather cool, worldly people who have well developed personal lives.

In my experience, a great many physicists think they are cool like Feynman, but are alas, many are not...

Re:quantum mechanics (0)

Anonymous Coward | more than 6 years ago | (#24491571)

an oxymoron indeed! but perhaps it'd be a qubit more wise to ask the poster to define his usage of "capacity" - what if the capacity defines a one qubit unit rather than a part of the system state itself? funny nevertheless :D

Re:quantum mechanics (1)

myrdos2 (989497) | more than 6 years ago | (#24492087)

Does this mean we can now send messages instantaneously using quantum entanglement? You have two particles that are entangled, each producing the same sequence of random values when measured. If we have two pairs of entangled particles, we have two channels and can therefore communicate faster than light speed?

Re:quantum mechanics (1)

Urkki (668283) | more than 6 years ago | (#24492611)

I think you still need the classical channel to make any sense of the information you receive, just like before.

Without classical channel, you still just have the ability to sync two completely random one-time-pads faster than light, with zero information content.

Somebody correct me if above is wrong.

Re:quantum mechanics (2, Interesting)

Renraku (518261) | more than 6 years ago | (#24492573)

Clearly the channels had SOME capacity for information transfer.

There are plenty of reasons why people don't understand quantum mechanics. Most people just don't care.

But I can list plenty of better reasons, for example, Calbi-Yau space. If you imagine the rubber-sheet model of the universe that everyone has seen in physics, replace it with this instead. Its pretty accurate as far as the math goes, and is a spin-off of QM. And then there are all of the various thought experiments, like Schrödinger's cat.

Can you tell that I'm an aspiring physics major?

Re:quantum mechanics (5, Funny)

Pollardito (781263) | more than 6 years ago | (#24492783)

don't worry, scientists also discovered that two people who don't understand quantum mechanics can engage in a meaningful conversation on the subject

FTL communications? (2, Interesting)

Xenographic (557057) | more than 6 years ago | (#24492847)

The real question in my mind is whether this allows for FTL communication, or whether nature conspires against that once again?

I believe it's Bell's inequality that prevents information from traveling faster than light. But each of these channels does NOT transmit information, if the paper is to be believed.

So, does that mean they could somehow be used with entangled photons or whatever to transmit information faster than light?

Encryption is anti-american (5, Funny)

Arthur B. (806360) | more than 6 years ago | (#24491069)

When you use quantum encryption, the theorists win !

Re:Encryption is anti-american (1)

Maavin (598439) | more than 6 years ago | (#24493637)

Funny
Incidentally I misread the RSS link:
"Terrorists Make Quantum Communications Break"

Simplified Quantum Physics (3, Insightful)

hpycmprok (219527) | more than 6 years ago | (#24491107)

Try not to look directly at it...

Two channels with zero capacity can carry info (5, Funny)

Anonymous Coward | more than 6 years ago | (#24491135)

It was called ISDN.

Re: Two channels with zero capacity can carry info (2, Insightful)

Jeffrey Baker (6191) | more than 6 years ago | (#24491367)

This is the most insightful comment ever made by AC.

Re: Two channels with zero capacity can carry info (1)

TheModelEskimo (968202) | more than 6 years ago | (#24492073)

LOL. Why you wouldn't log in to post that is a mystery to me.

Re: Two channels with zero capacity can carry info (1)

enoz (1181117) | more than 6 years ago | (#24492705)

A cynical person would say they did it so they could mod their own post up; or maybe they had already modded someone's posts and didn't want to waste the points.

Re: Two channels with zero capacity can carry info (1)

jacquesm (154384) | more than 6 years ago | (#24493011)

yes, but even a cynical person would have to admit, it *was* funny.

I think there's the D channel to thank for that actually ;)

For a second... (2, Funny)

LedIris (1331589) | more than 6 years ago | (#24491147)

I thought it said "Terrorists Make Quantum Communications Breakthrough".

Re:For a second... (3, Funny)

eggfoolr (999317) | more than 6 years ago | (#24491359)

When it comes to quantum mechanics, a theorist is not far removed from a terrorist!

Two Channels with Zero Capacity? (4, Funny)

Ralph Spoilsport (673134) | more than 6 years ago | (#24491157)

W y t a s u d l k a r a i e !

I c u d h l w t q a t m r p o r p y

h h t o n s i e g e t d a

t o l e p i h u n u c y t g a h .

RS

Re:Two Channels with Zero Capacity? (4, Funny)

Mr2001 (90979) | more than 6 years ago | (#24491201)

I demand you take that back. My grandmother was a saint!

Re:Two Channels with Zero Capacity? (1)

master5o1 (1068594) | more than 6 years ago | (#24491669)

i dont get it

Re:Two Channels with Zero Capacity? (1)

GrievousMistake (880829) | more than 6 years ago | (#24491707)

Sure, as soon as they find a way to work around the time skew problems caused by quantum whitespace collapse.

Re:Two Channels with Zero Capacity? (1)

moteyalpha (1228680) | more than 6 years ago | (#24491767)

Great demonstration. I couldn't have -not- said it better myself. It is something that is true in other areas and the relation ship of two zeros does have an effect on the outcome == 8 or perhaps infinity.

Re:Two Channels with Zero Capacity? (1)

Pantero Blanco (792776) | more than 6 years ago | (#24491887)

Nice, but I think you screwed up in your second and fourth lines.

"It could ehpliw..."

"It could help with quantum cryptography."

Re:Two Channels with Zero Capacity? (1)

rk (6314) | more than 6 years ago | (#24491997)

Was I the only network programming geek to see "htons" in there and find it impossible to let go of it in order to decrypt the actual message?

Re:Two Channels with Zero Capacity? (1)

jacquesm (154384) | more than 6 years ago | (#24493023)

hehe, I saw that first too, but then the phy at the end of the lines gave away the key, from there you can easily read backwards.

Re:Two Channels with Zero Capacity? (1)

vinn (4370) | more than 6 years ago | (#24491903)

I thought the big problem was key distribution, not actual transmission - and this doesn't seem to solve that problem.

Then again, I shouldn't even pretend to understand anything that starts with the word "quantum".

Zero plus Zero equals One for large values of Zero (4, Interesting)

LostCluster (625375) | more than 6 years ago | (#24491193)

I'm not sure how useful this is. The summaries seem to say that if you take two or more channels that have a signal to noise ratio of zero, there's some potential for binding them into a useful channel, but there's no indication of what kind of recovery rate there can be gained from this. Is this just error-correction applied to an extreme?

Re:Zero plus Zero equals One for large values of Z (5, Funny)

SpaceLifeForm (228190) | more than 6 years ago | (#24491931)

It's true.

You can extract immense amounts of information from the combination of Fox News (channel 0 with no signal) and the White House Press Secretary (channel 1 with no signal).

Anything in common is a lie, and that is useful information.

Re:Zero plus Zero equals One for large values of Z (3, Informative)

Pinky's Brain (1158667) | more than 6 years ago | (#24491961)

Not a S/N ratio of zero, their definition of channel capacity is only very tenuously connected to Shannon's channel capacity really. Quantum channels already have 0 capacity at non zero fidelity (the quantum equivalent to S/N). The 0 capacity channel from this paper aren't 0 capacity because of their fidelity though, the channels are 0 capacity for different reasons.

So it's not really directly applicable, "just" interesting math.

Re:Zero plus Zero equals One for large values of Z (1)

jhol13 (1087781) | more than 6 years ago | (#24492591)

I think this might be somehow linked to the fact that if we have two messages with zero information you can (trivially) combine them to have one message with full ("one") information.

Non-peer reviewed (4, Interesting)

4D6963 (933028) | more than 6 years ago | (#24491245)

Am I the only one who's worried that we keep getting 'news' from papers published on ArXiv, which is not a peer-reviewed source?

Just saying, it needs to be taken with a grain of salt.

Re:Non-peer reviewed (5, Informative)

Anonymous Coward | more than 6 years ago | (#24491699)

Most submissions to ArXiv do get submitted to peer-reviewed journals; this one claims to have been submitted in June (although they don't specify where). It's an opportunity for researchers to share their work without the delay of waiting for publication. Usually, papers there do get revised after going through the referee process.

Re:Non-peer reviewed (0)

Anonymous Coward | more than 6 years ago | (#24492039)

Damn - you beat me to it. Yes - this is a phenomenon that is a bit worrisome. The arxiv is a preprint archive, which means no peer review AT ALL is required to post something on it. The problem is, the general public (like most slashdot, digg, or reddit readers) don't have the qualifications to review a paper like this and spot any potential subtle errors. Similarly, most readers here wouldn't be qualified to generate an accurate abstract from most papers on the arxiv. That said, the arxiv is very useful -- primarily for scientific peers, not the general public.

Re:Non-peer reviewed (1)

jacquesm (154384) | more than 6 years ago | (#24493041)

no, god forbid the general public would have access to unvetted science, oh dear no.

You sound like someone trying to interpret the dead sea scrolls for the masses.

Re:Non-peer reviewed (5, Insightful)

c1t1z3nk41n3 (1112059) | more than 6 years ago | (#24492191)

We also get news from blogs, apple fan sites, and wikileaks. Non of those is peer reviewed either. The point is that it's not that people should take articles sourcing ArXiv with a grain of salt; it's that they should take everything with a grain of salt.

Re:Non-peer reviewed (1)

khallow (566160) | more than 6 years ago | (#24492391)

No. Most news comes from non-peer-reviewed sources.

I don't get it... (0)

Audent (35893) | more than 6 years ago | (#24491259)

what does it mean for my porn collection?

(this is a joke. Of course I don't have a porn collection, dear).

Do NOT look at this message!!! (4, Funny)

Bruce Perens (3872) | more than 6 years ago | (#24491265)

Oops, too late. You're entangled!

Re:Do NOT look at this message!!! (1)

rk (6314) | more than 6 years ago | (#24492011)

Just for God's sake don't open the box now. I don't want to find out I'm dead.

similarly, in computer science, (2, Insightful)

Khashishi (775369) | more than 6 years ago | (#24491337)

You can xor a random pad of 1s and 0s with some copyrighted data, and end up with a block of data which looks totally random. Neither the random pad or the encrypted block have any useful information when taken apart, but together they contain all the information of the copyrighted work.

Re:similarly, in computer science, (5, Funny)

Bryan Ischo (893) | more than 6 years ago | (#24491417)

Does the data really have to be copyrighted for that to work?

Re:similarly, in computer science, (1)

kvezach (1199717) | more than 6 years ago | (#24493515)

Yeah, otherwise it'll spontaneously decrypt. Now you understand the purpose of The Pirate Bay - it's there so that one may encrypt properly!

Re:similarly, in computer science, (1)

argent (18001) | more than 6 years ago | (#24491433)

Copyright is metadata. All you're saying is that encrypting a copyrighted work with a one-time-pad doesn't remove the copyright. Which is trivially true, since the copyright is not contained in the data.

Think of copyright like the chain of custody that you have to maintain in a court case. If you use a non-licensed agent to gather data, it weakens your case, even though the data is the same whether the agent is licensed or not... as the RIAA has recently discovered. :)

I think you've got it (5, Interesting)

ODBOL (197239) | more than 6 years ago | (#24491469)

I think that Khashishi has got the essence of the 0+0>0 thing here. I haven't completely penetrated the noise in the Smith/Yard ArXiv article yet, but I'd bet my money that it boils down to this:

Take two channels in each of which all bits are completely random, and independent of the information that you wish to send. Let each bit of your information determine the correllation or anticorrellation of corresponding bits in the two channels, by introducing a quantum constraint between them before their actual random values are determined. Then, as in Khashishi's description, the xor of the two random channels is the message.

The only difference I detect in Smith/Yard vs. Khashishi is that they use quantum trickery to make the whole thing look symmetric. Neither of the random channels predates the other. Each one, evaluated singly, appears to be completely independent of the encoded message. In Khashishi's description, the time sequence in the construction of the two random sequences makes one of them seem a priori random, and the other to be a one-time pad encoding of the message, while in the Smith/Yard article you can't tell which is which.

It seems more like a meretricious way of telling a causal story about a well-known phenomenon than something truly "essentially quantum."

Re:I think you've got it (2, Informative)

The Iso (1088207) | more than 6 years ago | (#24491945)

In Khashishi's description, the time sequence in the construction of the two random sequences makes one of them seem a priori random, and the other to be a one-time pad encoding of the message, while in the Smith/Yard article you can't tell which is which.

One-time pad ciphertext does appear to be random. Shannon proved that it has perfect secrecy.

Re:I think you've got it (2, Interesting)

ODBOL (197239) | more than 6 years ago | (#24492007)

<quote>

One-time pad ciphertext does appear to be random. Shannon proved that it has perfect secrecy.

</quote>

Right. But Smith/Yard make a stronger claim than randomness. They claim that the content of each channel does not depend on the message at all. Once the one-time pad is determined, the encoded message is determined completely by the plaintext. By encoding the plaintext into a quantum entanglement prior to the creation of either random channel, they are able to tell a story in which each channel's contents appear to be, not only random, but not functionally determined from the plaintext.

Re:I think you've got it (2, Informative)

SpazmodeusG (1334705) | more than 6 years ago | (#24492109)

The data looking random or not has nothing to do with the information capacity of the channel.
Shannons definition of information capacity is simply the maximum amount of information that can be recovered by the receiver on the channel.
A channel where the receiver can't recover data under any circumstances is a 0 capacity channel, that reason could be interfering noise or the fact that the channel doesn't exist.
Which poses a problem with this theory, it basically says 2 channels that don't exist can transmit information, which is intuitively incorrect.

Re:I think you've got it (1)

Randall311 (866824) | more than 6 years ago | (#24492363)

So basically all you have to do is qualify any theory with the word "quantum" and you can justify anything. Two channels that don't exist can all of the sudden transmit information. All of the sudden 0 + 0 = something more than 0. If this quantum stuff ever takes off then we are all in trouble. We'll have human sacrifice, dogs and cats living together... mass hysteria!

Re:I think you've got it (2, Funny)

jacquesm (154384) | more than 6 years ago | (#24493055)

> We'll have human sacrifice, dogs and cats living together... mass hysteria!

you mean like Los Angeles ?

Re:I think you've got it (1)

locofungus (179280) | more than 6 years ago | (#24493387)

The data looking random or not has nothing to do with the information capacity of the channel.
Shannons definition of information capacity is simply the maximum amount of information that can be recovered by the receiver on the channel.
A channel where the receiver can't recover data under any circumstances is a 0 capacity channel, that reason could be interfering noise or the fact that the channel doesn't exist.
Which poses a problem with this theory, it basically says 2 channels that don't exist can transmit information, which is intuitively incorrect.

I've only skimmed the paper but that's not what they are saying.

In classical information theory, if you have two channels, each with a capacity of 0 then the combined capacity of the channels is 0. It doesn't matter why each of the channels has a capacity of 0, whether that's noise, broken cable, etc. If you know the capacity of the channels you know the combined capacity.

Once we start transmitting quantum information things are harder. Just because each channel individually has a capacity of 0 doesn't *necessarily* mean that the capacity of the combined channels is also 0.

While this is only of theoretical interest at the moment its the sort of thing that could end up having practical consequences in the future. Someone has a quantum channel that's reaching capacity so they need to commission a new channel. By correctly specifying the new channel relative to the existing capacity they can actually add more new capacity than the new channel is capable of supporting.

This concept isn't completely unknown in the classical world. If you have a factory that needs electricity, you can supply the power on three phases using less conductor area than a single phase supply would need.

Tim.

Re:I think you've got it (3, Funny)

neomunk (913773) | more than 6 years ago | (#24492429)

Like putting too much air in a balloon! :-D

Re:similarly, in computer science, (4, Funny)

ObjetDart (700355) | more than 6 years ago | (#24491759)

...and if I combine your post with a random pad of 1s and 0s, will I get something that has anything to do with TFA?

Hmm... (2, Funny)

PPH (736903) | more than 6 years ago | (#24491389)

The summary didn't have any information on what a 'zero capacity channel' was. If I read it a second time, will I understand?

This is new? (5, Funny)

Quarters (18322) | more than 6 years ago | (#24491473)

I have DirecTV. That gives me something like six hundred channels which have zero intellectual capacity but yet still manage to carry data.

Quantum Telepnone Calls (4, Funny)

EEPROMS (889169) | more than 6 years ago | (#24491487)

Harry "Hello Jim Im ringing you back regarding the message you left on my voice mail." Jim "What message ? I hevent left one yet" Harry "Aw crap I did it again, I will never get my head around our new quantum telephone system"

Re:Quantum Telepnone Calls (3, Funny)

quinks (1172373) | more than 6 years ago | (#24492497)

"Hello Bob, this is Alice", Bob "Yeah, what is it", Alice "You left a message on my answering machine, but it's all garbled", Bob "Damn that Eve"

Terrorists? (1)

tankrshr77 (170422) | more than 6 years ago | (#24491589)

Am I the only one who read the headline as "terrorists"? That gave me a double take. That's just the headline McCain's been looking for.

Re:Terrorists? (1)

supernova_hq (1014429) | more than 6 years ago | (#24491941)

Damn, somebody beat me to it!

Does that mean... (1)

orionop (1139819) | more than 6 years ago | (#24491645)

my comment is both here and not here simutaniously?

Just like in C (0)

Anonymous Coward | more than 6 years ago | (#24491647)

Code fragment:

int a = 15/20;
int b = 15/20;
int c = a + b;
int d = (15 + 15) / 20;
printf("%d",d-c);

Result: 1

Original article here: (2, Interesting)

gardyloo (512791) | more than 6 years ago | (#24491715)

http://arxiv.org/PS_cache/arxiv/pdf/0807/0807.4935v1.pdf [arxiv.org]

    Interesting, but the paper seems to have a nasty habit of simply redefining what "capacity" means in a quantum context, to basically, "Well, if we have two interacting channels, one changes the other to have non-zero capacity." And if I interpret it that way, it simply rewords the problem to be different from the original interpretation. Also, there's a significant amount (even for an arxiv paper) of speculation present (which is interesting!). From the paper: Nonetheless, each channel has
the potential to \activate" the other, effectively cancel-
ing the other's reason for having no capacity. We know
of no analog of this effect in the classical theory. Per-
haps each channel transfers some different, but comple-
mentary kind of quantum information. If so, can these
kinds of information be quantfied in an operationally
meaningful way? Are there other pairs of zero-capacity
channels displaying this effect? Are there triples? Does
the private capacity also display superactivation? What
new insights does this yield for computing the quantum
capacity in general?

    One "classical" analogy is that of orthogonally-crossed polarizers, which, upon insertion of another polarizer with principle axis somewhere between that of the originals, will allow light to shine through where none was before.

Re:Original article here: (2, Informative)

oldhack (1037484) | more than 6 years ago | (#24492315)

So it's like this?

a = -i
b = i

real(a) = 0
real(b) = 0
real(a * b) = 1

where i = imaginary number, guess it may represent the hidden (from us) quantum dimension/domain, like wave function.

Alrighty (1)

gcnaddict (841664) | more than 6 years ago | (#24491753)

So it's basically a mindfuck, just like the rest of quantum theory.

I'm kinda surprised this wasn't tested before. You'd think all the mindfucks would be checked since it's basically maybe opposite day over in quantum-land.

But Quantum information can be negative! (2, Funny)

SpazmodeusG (1334705) | more than 6 years ago | (#24491757)

Because quantum information can be negative it would seem this theory could be applied to make a channel with 0 negative capacity have some cpacity from nothing in the same way.
So really any extra positive capacity could be cancelled out.

Re:But Quantum information can be negative! (1)

SpazmodeusG (1334705) | more than 6 years ago | (#24492979)

Damn i'm getting modded funny but i'm serious. There's a paper on negative quantum channels by Horodecki who's earlier work is referenced in this current paper.
link: http://arxiv.org/abs/quant-ph/0505062 [arxiv.org]
Basically a channel that doesn't exist can be thought of as both a channel of 0 positive information capacity and as a channel of 0 negative information capacity.
The negative channel can be treated in the exact same way as the positive channel. Once you have worked out the net capacity of each the total capacity is the positive channel - the negative channel.
So when this paper says that you can use a 0 capacity channel for information transfer, there is a paradox as a 0 capacity channel can be thought of as a channel that doesn't exist.
In this case the positive information capacity of 2 channels can be increased, but i beleive that the negative information capacity would also increase in exactly the same way.

Re:But Quantum information can be negative! (1)

Maavin (598439) | more than 6 years ago | (#24493657)

Obviously, information on TV can be negative, too...
As watching specific channels increases stupidity :)

um (1)

drDugan (219551) | more than 6 years ago | (#24491855)

FTA... "points to the existence of incomparable types of quantum information"

mind blowing...

The Quantum Message From the Aliens... (1)

gishzida (591028) | more than 6 years ago | (#24492059)

This just in to the ./ news wire: A message from aliens has been discovered and decrypted using 157 Channels of vacuous cable TV. The message reads: "Wer in ur pr0n and pwn ur ipod."

Speaking in metaphors... (1)

fahrbot-bot (874524) | more than 6 years ago | (#24492211)

... two quantum channels with zero capacity can carry information ...

Meaning two blondes make a brunette?

Re:Speaking in metaphors... (2, Funny)

tftp (111690) | more than 6 years ago | (#24492421)

Meaning two blondes make a brunette?

Only if they are of different gender, and with 25% [wikipedia.org] chance :-)

Re:Speaking in metaphors... (0)

Anonymous Coward | more than 6 years ago | (#24492493)

Just because someone said "quantum" doesn't mean that blonde is now the dominant trait or that 0+0=1.

Oh, well actually it does mean that 0+0=1. But whatever you said is still wrong.

Just think what you could do with quadraphonic (1, Insightful)

rossdee (243626) | more than 6 years ago | (#24492323)

If "two quantum channels with zero capacity can carry information when used together" then how much information could you send with 4 channels? Of even 2 channels with some (>0) capacity?

Would that end up with an infinite ampunt of information, or just all the information in the universe?

Maybe you'd get a 'beep' of all the messages ever sent by this method (like the beep you get from a dirac receiver in James Blish's story).

So... (1)

acedotcom (998378) | more than 6 years ago | (#24493015)

...by using two channels it works like download accelerator plus and dial-up. I knew SOMETHING would make DAP work, and it was quantum mechanics.

Need a break (0)

Anonymous Coward | more than 6 years ago | (#24493113)

Man, i need a break from the news, i swear i read the headline as 'terrorists make ....', and then i was like 'that's odd, how could a small band of underfunded terrorists be ahead of western science in quantum physics..'

Quantum communication is like... (1)

Perf (14203) | more than 6 years ago | (#24493313)

You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat. -- Einstein

And quantum communication operates in exactly the same way. The only difference is that they use Schrödinger's Cat.

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