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Quantum Telecloning Demonstrated?

ScuttleMonkey posted more than 8 years ago | from the nosey-people dept.

195

An anonymous reader writes "According to Physorg eavesdropping on a quantum encrypted link can now be done without detection. From the article: 'The scientists have succeeded in making the first remote copies of beams of laser light, by combining quantum cloning with quantum teleportation into a single experimental step. Telecloning is more efficient than any combination of teleportation and local cloning because it relies on a new form of quantum entanglement - multipartite entanglement.' There is also a PDF of a related paper available here for background material."

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FP (-1, Offtopic)

Anonymous Coward | more than 8 years ago | (#14757972)

FP

Oh (-1, Flamebait)

Anonymous Coward | more than 8 years ago | (#14757976)

That explains everything.

What it all really means (-1, Troll)

Anonymous Coward | more than 8 years ago | (#14757992)

What it means is that never-discussed capabilities of submarines to tap fibre optic cables at the bottom of the ocean is true.

You can tap fibre without the other party knowing. What I question, is how long has this been known at the NSA?

I hear the faint wisper of black helicopers in the distance. NOT AGAIN!!!!

NO CARRIER

Re:What it all really means (2, Funny)

shokk (187512) | more than 8 years ago | (#14758266)

DAMMIT! Now I have encrypt my files all over again!
Hopefully that Quantum Pretangle Cloning will stay unscannable.

Ummm... (-1, Offtopic)

node159 (636992) | more than 8 years ago | (#14757997)

ZOMGUH4>0RDMYINTERWEB!!!!

I really dig this stuff... (5, Funny)

Mark_Uplanguage (444809) | more than 8 years ago | (#14758002)

but I'm starting to get discouraged now that the already hard to grasp concepts of quantum mechanics are being infused with new more complicated forms. In the end I just want to know if we can teleport ourselves cause I'm tired of my f'ing commute.

Re:I really dig this stuff... (4, Funny)

websaber (578887) | more than 8 years ago | (#14758064)

I remember the good old days when unbreakable encryption would stay unbreakable for 15 years. Now it's being broken before it is even released.

Well, don't they need a pre-publication license? (1)

CDMA_Demo (841347) | more than 8 years ago | (#14758165)

if you remember: http://tinyurl.com/ozw7f [tinyurl.com]
another karma abuse.

Re:I really dig this stuff... (3, Funny)

skoaldipper (752281) | more than 8 years ago | (#14758230)

Various scenarios and their solutions!

By no means can two perfect copies of people be allowed to exist at the same time. It would rip apart the very fabric of space time as we know it. Therefore...

1. Materialize two pugil sticks into the data stream, one for each person. Let them duke it out American Gladiator style. Loser gets fed into a tree shredder (provided by Soylent Green Technologies).

2. Insert shark teeth and monkey tail DNA into the copy. He would be slightly different, and slightly cooler too. Men, otherwise wasteful empty beer cans now provide roughage as well. Ladies, flexible long second appendage for you. Think about it. 'Nuff said. Order preserved.

3. Keep both the original and copy. #$%@ the Universe! Take a chance. The Colossal Crumple is merely 5 billion years away anyway...

Re:I really dig this stuff... (1)

slashbob22 (918040) | more than 8 years ago | (#14758293)

This article doesn't talk about teleporting. It talks about telecloning which would be even better. I can now create multiple clones of myself and have them do work while I have a "Sexy Party" - Stewie Style!

Re:I really dig this stuff... (1)

cosinezero (833532) | more than 8 years ago | (#14758542)

A sexy party ... with clones of yourself?

Re:I really dig this stuff... (1)

timbck2 (233967) | more than 8 years ago | (#14758644)

Hey, it worked in The Man Who Folded Himself [amazon.com] by David Gerrold.

Re:I really dig this stuff... (2, Funny)

DigitalReality (903767) | more than 8 years ago | (#14758357)

Everything will take less than 1 second, but the DMV will still take like 9 seconds.

Re:I really dig this stuff... (1)

LilGuy (150110) | more than 8 years ago | (#14758579)

Hahaha... who was it that said that line?

Re:I really dig this stuff... (1)

DrEldarion (114072) | more than 8 years ago | (#14758596)

I think it was Dane Cook.

It is not "encryption", it is "modulation"! (3, Interesting)

gweihir (88907) | more than 8 years ago | (#14758006)

Encryption is a mathematical transformation. Quantym "encryption" has no mathematical transformation in it, it is just a way of modulating signals, i.e. a physical process! That is called "modulation" and has no security properties besides the physical signal properties. No mathematical proofs about this security can be given, since we still do not unterstand the physical universe completely!

Since all previous claims of security rested on not yet well understood physical principles, I am not surprised that once again claims of perfectness by ethically challenged researchers and businesspeople have turned out to be wrong.

Re:It is not "encryption", it is "modulation"! (4, Informative)

Secret Rabbit (914973) | more than 8 years ago | (#14758134)

No mathematical proofs about this security can be given, since we still do not unterstand the physical universe completely!
Perhaps you haven't read:

http://www.amazon.ca/exec/obidos/ASIN/0521635039/q id%3D1140401059/701-1812336-3224355 [amazon.ca]
I am not surprised that once again claims of perfectness by ethically challenged researchers and businesspeople have turned out to be wrong.
Perhaps you are not aware of a phrase that states "within current theory" that is implied everytime a theorist speaks. Or weren't you aware of that?

Or how about all those classical encryption schemes that were thought to be secure for long periods of time, but them turned out to be [near] trivial to break.

New attacks are created all the time. It doesn't mean the the researcher is ethically challenged. It just means that he thought he was right at the time, given the information at hand.

This is cutting edge research. Get a clue. Or at least your head out of your ass.

Re:It is not "encryption", it is "modulation"! (2, Interesting)

jfredett (955797) | more than 8 years ago | (#14758206)

Beng somewhat of a mathematician and crypto-buff, let me say this.

Firstly, it IS encryption, there is data being hidden in a non-obvious format,

Dictionary.com says this about the term "Encrypt"

encrypt
tr.v. encrypted, encrypting, encrypts

      1. To put into code or cipher.
      2. Computer Science. To alter (a file, for example) using a secret code so as to be unintelligible to unauthorized parties.

I see nothing about mathematical transforms there. In fact, many ciphers are not mathematical at all, some are completely visual, take for instance Transpostition ciphers, like the hedgerow cipher, (every other letter is taken out and shifted to the end). There is no mathematical transform that you use, no numbers are assigned. Now, notably, you can describe THIS cipher using group theory (it a morphism on a group), however, It can be done with no knowledge of any math at all.

Second, Slightly less of this topic, this is terribly intresting, as the quantum encryption scheme was touted as "completely" unbreakable. And now its been cracked before its even been used. I wonder if anyone will come up with something stronger before (if they ever get to the point where they are usable) Quantum computers invalidate RSA and other factorization based ciphers...

Any other articles out there about different types of quantum encryption?

Re:It is not "encryption", it is "modulation"! (1)

Lehk228 (705449) | more than 8 years ago | (#14758657)

*sigh*

yes a physical manipulation is mathematical, there is geometry , graph theory, and discrete math involved.

Re:It is not "encryption", it is "modulation"! (1)

JohnnyBigodes (609498) | more than 8 years ago | (#14758150)

No mathematical proofs about this security can be given, since we still do not unterstand the physical universe completely!

Absolutely! Because since it's quantum mechanics we're talking about, any mathematical proof *might* or *might not* be true :p

Re:It is not "encryption", it is "modulation"! (5, Informative)

wwwrench (464274) | more than 8 years ago | (#14758158)

Wrong.
All the article claims is that the Evesdropper's location will be undetected. The fact that someone is attempting to eavesdrop will still be detected, and there are several well known proofs of security of this fact.
FTF Press Release
"Quantum cryptographic protocols are so secure that they can not only discover tapping but also where and how much information is leaking out. Now, using telecloning, the identity and location of the eavesdropper can be concealed."
Quantum cryptography is absolutely secure as long as the laws of quantum mechanics are true. And even if the laws of quantum mechanics are false, one can still do secure cryptography from some very weak assumptions (it follows from violating Bell's inequalities and no-signalling) see this [lanl.gov]

Re:It is not "encryption", it is "modulation"! (2, Insightful)

MyNymWasTaken (879908) | more than 8 years ago | (#14758352)

Thank you for forcing me to go back and re-read the article. I misread it, as did the submitter, and was extremely confused.

The eavesdropper is still detected. The blurb is wrong.

eavesdropping on a quantum encrypted link can now be done without [detection (wrong)] being located

Re:It is not "encryption", it is "modulation"! (1)

Lehk228 (705449) | more than 8 years ago | (#14758664)

the problem with quantum crypto is that it requires the components to be installed together and securely, if you are doing that you may as well simply use abnormally large symmetric keys.

Re:It is not "encryption", it is "modulation"! (5, Informative)

tbo (35008) | more than 8 years ago | (#14758668)

Disclaimer: IAAQIS (I Am A Quantum Information Scientist).

The parent poster (wwwrench) is completely, 100% correct. Is this really Slashdot, or did I type the wrong URL?

Seriously, though, the parent poster is bang-on. To elaborate a bit, quantum cryptography would be more informatively called quantum key distribution (although both names are common in practice). All it does is allow you to distribute a key for a one-time pad in a secure method, given that the laws of quantum mechanics are at least partially correct (one-time pads are information-theoretic secure, provided the key is not compromised or re-used). If somebody tries to eavesdrop, you can detect it, and respond accordingly. That response could be privacy amplification (if the information the eavesdropper gained was only partial), re-trying the protocol, or bombing the eavesdropper to smithereens. That last possibility is why quantum telecloning might be useful.

One other hitch is that quantum key distribution requires a small shared secret in order to authenticate the two parties trying to generate a key. Thus, quantum key distribution is not a complete replacement for public-key cryptography.

Re:It is not "encryption", it is "modulation"! (0)

Anonymous Coward | more than 8 years ago | (#14758326)

That is called "modulation" and has no security properties besides the physical signal properties.

Modulation has nothing to do with physical properties. It is a means of encoding data through change. That encoding may or may not happen through physical signals. A modem changes a carrier wave to encode data. The actual data is represented by the way in which the signal differs from the carrier.

But modulation does not have to apply to physical characteristics. One could, for example, modulate the amount of bandwidth a network connection uses. If network utilization is significantly greater than the norm, the data is a one. If utilization is the norm, the data is a zero. In practice, one would use statistics to measure these things, and forward error correction to deal with the inevitable flaws from the low signal-to-noise ratio.

All kinds of other things can be modulated. Such as processor utilization, file sizes, spelling, time-stamps, response time, etc.

Despite your pleas that modulation has no security properties it is worth noting the above-mentioned forms of modulation have been used as covert channels to transmit data without detection.

saw it coming (2, Funny)

Anonymous Coward | more than 8 years ago | (#14758017)

I knew this was gonna happen. I kept telling everyone it was just a matter of time.

ahh yes (4, Funny)

la htris (955271) | more than 8 years ago | (#14758021)

so now we can listen in on quantum encrypted... wait a second... that doesn't exist yet.

O well, must be the FBI getting an early start.

Re:ahh yes (1)

gbobeck (926553) | more than 8 years ago | (#14758235)

Sure it exists, just not necessarily in every universe.

Next you'll be telling me that Schrodinger's Cat is alive. Wait, dead... Wait, alive...

news flash! (2, Funny)

la htris (955271) | more than 8 years ago | (#14758332)

SCHRODINGER'S CAT FOUND HALF ALIVE
Quantum Theory Wrong

at least, half the cats are alive

Re:ahh yes (4, Informative)

kebes (861706) | more than 8 years ago | (#14758361)

I think you're confusing quantum computing [wikipedia.org] (which is still mostly theoretical... the largest experimental proof has only involved a few qbits, and for all we know a full-fledged computer will be impractical) and quantum cryptography [wikipedia.org] , which actually has been experimentally demonstrated.

Amazing as it may sound, researchers have used commercially available fiber-optics to send quantum encrypted signals. There are even companies that will sell devices, although right now the tech is not quite ready for prime-time. Still, it has been shown in a laboratory many times, and it's not fanciful to say that it may be deployed within our lifetimes (just depends on when the technology becomes affordable, compared to its benefits).

Also, as others have pointed out, this new result actually doesn't show that quantum crypto is breakable... it only shows that under some circustances the eveasdropper can remain anonymous... but the users of the channel will still know that it has been compromised, and will thus not use the keys that have been generated. That is, quantum crypto is still mathematically unbreakable when properly implemented (assuming that Quantum Mechanics is correct, that is).

Re:ahh yes (4, Informative)

Anonymous Coward | more than 8 years ago | (#14758621)

http://en.wikipedia.org/wiki/Quantum_entanglement [wikipedia.org]

If the composite system is in this state, it is impossible to attribute to either system A or system B a definite pure state. Instead, their states are superposed with one another. In this sense, the systems are "entangled".

Now suppose Alice is an observer for system A, and Bob is an observer for system B. If Alice performs the measurement A, there are two possible outcomes, occurring with equal probability:

      1. Alice measures 0, and the state of the system collapses to |0\rangle_A |1\rangle_B
      2. Alice measures 1, and the state of the system collapses to |1\rangle_A |0\rangle_B.

If the former occurs, any subsequent measurement of B performed by Bob always returns 1. If the latter occurs, Bob's measurement always returns 0. Thus, system B has been altered by Alice performing her measurement on system A., even if the systems A and B are spatially separated. This is the foundation of the EPR paradox [wikipedia.org] .

The outcome of Alice's measurement is random. Alice cannot decide which state to collapse the composite system into, and therefore cannot transmit information to Bob by acting on her system. (There is a possible loophole: if Bob could make multiple duplicate copies of the state he receives, he could obtain information by collecting statistics. This loophole is closed by the no cloning theorem, which forbids the creation of duplicate states.) Causality is thus preserved, as claimed above.

http://en.wikipedia.org/wiki/No_cloning_theorem [wikipedia.org]

The no cloning theorem is a result of quantum mechanics which forbids the creation of identical copies of an arbitrary unknown quantum state. It was stated by Wootters, Zurek, and Dieks in 1982, and has profound implications in quantum computing and related fields.

Note that the state of one system can be identically entangled with the state of another system, such as by using a CNOT gate, but this does not constitute cloning since the systems will always yield the same value upon measurement. The no cloning theorem describes the inability to make separately measurable states.

What? (4, Insightful)

compuguy84 (886540) | more than 8 years ago | (#14758027)

I was just gonna say that...

Seriously though, no matter how much I learn/study/pay tuition, there're always posts that make me realize how little I know about anything.

It's both humbling and inspiring.

Off topic, but someone had to say it... :)

Don't worry... (4, Funny)

NotQuiteReal (608241) | more than 8 years ago | (#14758037)

Don't worry. No matter how hard you try to know anything, you'll still be dead soon, in the cosmic scheme of things.

Have a nice day!

Re:Don't worry... (1)

skoaldipper (752281) | more than 8 years ago | (#14758271)

13,884 days left for me, and counting! Not really so many, even in the earthly scheme of things.

And thanks. I will have nice days! Peace. See you on the other side real soon my friend!

Heisenberg Uncertainty Principal? (5, Interesting)

icleprechauns (660843) | more than 8 years ago | (#14758028)

What ramifications does this have on the heisenberg uncertainty principal? I may be no expert, but doesn't this mean that you could make a remote copy of a particle, and measure one's momentum and the other's position with great accuracy?

Re:Heisenberg Uncertainty Principal? (1)

Monkofdoom (928921) | more than 8 years ago | (#14758048)

My names Monk and i don't understand much :(

Re:Heisenberg Uncertainty Principal? (3, Funny)

Solder Fumes (797270) | more than 8 years ago | (#14758053)

There IS NO Heisenburg Uncertainty Principal.

Unless there is a school named Heisenburg Uncertainty, which would be cool.

Re:Heisenberg Uncertainty Principal? (5, Funny)

LiquidCoooled (634315) | more than 8 years ago | (#14758188)

There is such a place, but the lesson plan is a nightmare.
Just as you think you know where your next lesson is you rush to get there to realise you've already missed it.

Finding out if the lecturers are still alive after opening the classroom door is an entirely different and wholey worrying scenario unto itself.

Re:Heisenberg Uncertainty Principal? (2, Funny)

Krakhan (784021) | more than 8 years ago | (#14758415)

Oh that's nothing. You should hear about my visit to Hilbert's Grand Hotel...

Are you sure? (1)

leonbrooks (8043) | more than 8 years ago | (#14758699)

(deem g/d/r implied)

Re:Heisenberg Uncertainty Principal? (1)

BSAtHome (455370) | more than 8 years ago | (#14758054)

Yes, but is the clone entangled with the original? If so, all if fine again and Heisenberg still is right. Only if the clone is independent, then were at creating a new view of the universe.

Re:Heisenberg Uncertainty Principal? (1)

diamondsw (685967) | more than 8 years ago | (#14758092)

I'm not sure Heisenberg is a principal either.

Re:Heisenberg Uncertainty Principal? (1)

la htris (955271) | more than 8 years ago | (#14758105)

Interesting point, although how would telecloning make this any more possible than quantam cloning? Heisenberg Uncertainty Principal talks also about wave particle duality (if you dont know what im talking about wikipedia is reasonably complete about it http://en.wikipedia.org/wiki/Uncertainty_principle / [wikipedia.org] . Really the principle is concerned with two "conjugate" variables, commonly it is just thought of with regards to position and momentum, but it also applies to things such as energy vs time. also just because you clone a particle at an instant doesnt mean they will still be identical an instant later when you measure the two things.

the cloning is only approximate (4, Informative)

wwwrench (464274) | more than 8 years ago | (#14758306)

The reason that it doesn't violate the Heisenberg uncertainty principle is that the cloning is only approximate. You have one good photon, and you create two copies, neither of which are like the original. They are only somewhat like the original. This means that the evesdropper will get detected. Telecloning, just means that you clone the photon (approximately), and move it to another location (cloning+teleportation). The article claims that this means the location of the evesdropper will thus be safe, even if her attack is noticed. The article is actually about an experimental realisation of telecloning, not the discovery of telecloning itself.

Re:Heisenberg Uncertainty Principal? (4, Funny)

Concerned Onlooker (473481) | more than 8 years ago | (#14758317)

What ramifications does this have on the Heisenberg uncertainty principle?

Obviously no one is quite sure.

Re:Heisenberg Uncertainty Principal? (0)

Anonymous Coward | more than 8 years ago | (#14758354)

That's a real good question, I was wondering the same thing.

As a side note, it would be nice if they could manage to use this to benefit humanity instead of worrying about how it will affect encryption and stuff.

Re:Heisenberg Uncertainty Principal? (4, Informative)

da cog (531643) | more than 8 years ago | (#14758447)

Actually, if it could be done it wouldn't violate the Uncertainty Principle at all. A particle cannot have both a definite momentum and position, it can only have (roughly speaking) a probability distribution of each. So if you could clone a particle a zillion times, then each time you wouldn't get the same position, but rather if you looked at all of the clones together you'd get a distribution which would be identical to that of the original particle.

Having said that, cloning a particle perfectly is nonetheless forbidden by the No Cloning Theorem [wikipedia.org] . Basically (as I understand it) what this says is that there is an underlying principle of Quantum Mechanics that you can never know what position distribution a particle originally had, since the moment you measure it you focus it at that point and kill the original distribution. Cloning the particle would be a way of "cheating" that would let you get the distribution of the particle without destroying it, so it ends up being forbidden.

Now, even though you cannot perfectly clone a particle, you can imperfectly clone it, which is what these guys have claimed to have done. If you look at the abstract, you will note that they are only claiming a fidelity of 58% +/- 1%. (The theoretical limit is five-sixths (83%) according to this article in New Scientist [newscientist.com] .)

A non-perfect fidelity, however, isn't so bad. Alice and Bob probably can't get their own optimal fidelity when using Quantum Cryptography anyways; in theory they should expect to see 50% of the bits get through, and then worry if they see it goes down below that -- even, say, to 49%. In practice, their equipment might only be able to get 40% of the bits through, and sometimes even less than that, so they'll tolerate lower rates than 50% since they are figuring that eavesdropping would lower this rate all the way down to 25%, and that is something that they'd surely notice. However, by using the techniques like those discussed in the article you can apparently eavesdrop less than perfectly in a way that, while still lowering the bit transmission, does not make it as bad as 25%. Thus, if Alice and Bob were naive they'd just assume that their equipment was faulty and not that there was an eavesdropper.

So the moral of this story is that from now on Alice and Bob will have to make their apparatus work much more reliably so that they can expect a success rate of say, 45-50% rather than 35-50%, and thus be more likely to notice a slight degradation in the signal due to an eavesdropper.

Quantum Transmission (2, Insightful)

gadzook33 (740455) | more than 8 years ago | (#14758045)

It's always bugged me that they call it quantum encryption since it's really classical encryption used in a quantum transmission role. I don't see anything "quantum" about the encryption itself. Of course, it probably sounds cooler that way...

Re:Quantum Transmission (1)

kebes (861706) | more than 8 years ago | (#14758410)

Although the encryption scheme itself just uses a classical key, the transmission of the key is done over a public channel using a quantum trick. Normally you would be crazy to just transmit the key over a public channel, but by using entangled particles (photons or whatever), you have a mathematically and physically rigorous proof that the transmission was sent without being intercepted. Thus, you know that the end-party received the key without anyone else getting a copy. If some third party does manage to evesdrop, you'll know about it (because of the way quantum entanglement works), and you'll discard the key and create a new one (and repeat as many times as needed until you're satisfied that the key is secure). Yes I'm very much glossing over the details...

The point is that the secure transmission of the key is a uniquely quantum event. You would not be able to do this without using entangled particle pairs. That's why it is a "classical encryption/quantum key transmission scheme" or "quantum cryptography" for short. I won't argue that calling it "quantum cryptography" is over-simplifying the issue, but saying that "it's just classical encryption using a quantum transmission" misses a key point: the quantum transmission is what guarantees that the key distribution is secure! Without that security, the "cryptography" isn't cryptography at all.

Another basic law of physics... (2, Funny)

NotQuiteReal (608241) | more than 8 years ago | (#14758060)

If someone says something, someone might overhear it.

I just made that up, but the obvious corollary is this; If you don't want something to be known, don't say it!

Thank you very much, I'll be here all week. (Mostly because I have nowhere else to go.)

Re:Another basic law of physics... (1)

TubeSteak (669689) | more than 8 years ago | (#14758379)

Thank you very much, I'll be here all week. (Mostly because I have nowhere else to go.)
You left out the line about tipping the waitresses.

They hate it when the 'funny' guy forgets to do that. When they're not happy, management isn't happy, and when management isn't happy... well, lets just say you should probably find someone else to go.

I hear Kuro5hin is looking for some new talent.

Quantum Encryption Eavesdropping? (0)

Anonymous Coward | more than 8 years ago | (#14758067)

Well, I for one welcome our quantum encryption link eavesdropping overlords...

bit34 (-1, Flamebait)

Anonymous Coward | more than 8 years ago | (#14758070)

Let's keepj to with any sort Both believed that

Can I get this in English? (4, Funny)

ip_freely_2000 (577249) | more than 8 years ago | (#14758072)

Most of the time, I at least read TFA and make a dumb comment. This time, I read TFA and just felt dumb.

Can some explain it and use real-world examples?

Re:Can I get this in English? (0)

ZachPruckowski (918562) | more than 8 years ago | (#14758347)

Basically, the one hope we ever had at unbreakable communications just got P3WNed. Whereas current telecommunications can be intercepted and copied along the way (called packet sampling at the ISP level I think), this would have been impossible with quantum encryption. But they found a way to listen to it without changing it, at least as I understand it.

Re:Can I get this in English? (2, Informative)

QuantumG (50515) | more than 8 years ago | (#14758440)

You understand it as such because you didn't even read the article. Now shut your hole.

LOL (0)

Anonymous Coward | more than 8 years ago | (#14758567)

Glad to see you know more than just viruses ;)

Appreciate your stuff back in the day. I sure learnt a lot.

All right, you're on (1)

Ruberik (935611) | more than 8 years ago | (#14758431)

Let me see if I can explain this in English, with minimal math. (ed: not without taking a page)

First, I should make it clear that this isn't a dramatic new idea or a new "take" on quantum physics. That being said, it's pretty neat. Like quantum teleportation or quantum computing, it's the sort of thing that you know is theoretically possible, but is still very exciting when somebody does it.

Let's talk about three things: quantum teleportation, quantum cloning, and quantum telecloning.

I'm going to talk about everything in the context of "qubits," quantum bits. As anyone reading this probably already knows, a normal bit can have the states 0 and 1; so can a qubit, though we call them |0> and |1>. Unlike a bit, a qubit can also have intermediate states, like (|0> + |1>). [*] As you also may know, whatever the qubit's state is -- |0> + |1>, |0> - |1>, 1/2 |0> + sqrt(3)/2 |1>, or whatever -- if you measure the qubit, you'll get either |0> or |1>, and no indication of what state it was in previously.

That's why we need QUANTUM TELEPORTATION. Suppose I have a qubit in state A = a|0> + b|1>, and I want to send it to you on the other side of the world. Even supposing that I knew what my state was -- and if I don't, I can't find out -- it would take a long time to transmit a and b, since they're arbitrary real numbers. Quantum teleportation is the transmission of an exact copy of A from me to you. We need to start off with some entangled qubits that we made last time we met, but for the moment we'll assume that we have those.

So what is QUANTUM CLONING, and why isn't teleportation it? Well, teleportation has the unfortunate feature that if I want you to have a copy of A, I have to destroy my copy of it in the process. Ideally, what quantum cloning would do is give you and me each a copy of A. Unfortunately, you can't do that: there's something called the No Cloning Theorem [**] that expressly forbids doing that. The best you can do with quantum cloning is make a copy that isn't only a copy; it's entangled with the original. What that means is if I measure my copy of A and get |0> or |1>, your copy is stuck with the same result: if I got |0>, you'll get |0>. Mathematically, we start with a|0>|0> + b|1>|1>, and measuring with result |1> will change that to |1>|1>. So it's a clone, but the clones' destinies are intertwined.

There's another post where someone asks about Heisenberg's Uncertainty Principle: could I use this to make two copies of A, and measure the position of one and the momentum of the other? Well, you could, but it would be exactly equivalent to just taking A and measuring its position and then its momentum. By measuring, you change the state of both copies.

So now we bring all this together, with QUANTUM TELECLONING. We're going to do quantum teleportation just like before: you and I already shared some entangled qubits ahead of time, and we want to teleport. But this time, instead of just a pair of entangled qubits, we have a triplet: I got one of the qubits, and you and my MSc supervisor Bill each got one. Now when I send A to you both, you get a copy and Bill gets a copy (and I lose mine), just like in quantum teleportation. But the copies you have are clones as I discussed above: if either of you ever makes a measurement, it will affect the other's state.

The application of this to quantum communication is that I can throw a wiretap into your communication line, and through this technique I can clone a copy of your qubit for myself -- and also let you have an exact copy of the original go through unimpeded. So what does this do to quantum cryptography? To be honest I'm not sure, but it's clearly not quite like you're just another receiver. I'm going to a lecture on this either tomorrow or Tuesday, so I'll post a followup then. You can also contact me at slashdotphysicist at geemail if you're interested in more.

[*] There should be a /sqrt(2) there, but I'm omitting normalization here for simplicity.
[**] http://en.wikipedia.org/wiki/No_cloning_theorem [wikipedia.org] . Do we really know that this is right? No, but it lives and dies with quantum mechanics. If it's wrong, then we've got much bigger issues than the collapse of quantum cryptography.

Re:All right, you're on (1)

Ruberik (935611) | more than 8 years ago | (#14758477)

A correction: I just followed the paper trail back and discovered that it isn't talking about cloning as I discussed above: it's talking about cloning as one would normally imagine it (actual copies), but with limited fidelity. If you want to get above the ceiling on fidelity, you have to start entangling your states as per my discussion of cloning above. Please save me some embarrassment by not modding the parent up. :-)

(The paper in question: http://www-users.cs.york.ac.uk/~schmuel/papers/LBb 01.pdf [york.ac.uk] )

Okay (0)

Anonymous Coward | more than 8 years ago | (#14758450)

Yeah

a) Experiment demonstrates previously theorized quantum telecloning which is one way to get an approximation of transmitted bits (simply, u can get X more bits correct than just guessing).
b) The quantum No Cloning Theorem is still safe and not violated, no need to get hysterical or pissed off. This is because No Cloning Theorem only forbids exact copies.
c) Fidelity was 58%

Experiment makes, without a doubt, a valuable contribution although didn't overturn fundamental theory.
Imho, Quantum cryptography still viable due to privacy enhancement techniques. Read more on that here http://www.ai.sri.com/~goldwate/quantum.html [sri.com]

As a physics major... (4, Funny)

physicsphairy (720718) | more than 8 years ago | (#14758081)

As a physics major who has taken the time to look over the paper (read: barely skimmed--I am a lazy college student afterall), I would just like to offer my sincere opinion of "HUh?"

I hope that will be helpful to other Slashdotters outside the field.

Re:As a physics major... (1)

MyNymWasTaken (879908) | more than 8 years ago | (#14758140)

I whole-heartedly agree with you. I was a physics major too; long long ago.

"Remember all that stuff we told about undetectable eavesdropping on a quantum transmission being impossible by definition, well... uhhm... we just did it."

Whatthafu?

As a physics graduate student... (1)

MustardMan (52102) | more than 8 years ago | (#14758638)

Let me say "physorg sucks"

This particular quote made me particularly amused...

Telecloning combines cloning (or copying) with teleportation (i.e., disembodied transport). (emphasis mine)

Disembodied transport? WHAT? Quantum teleportation is NOTHING like the star trek fantasy these idiots are building it up to. This isn't some matter/energy conversion to move physical objects - it's FRICKIN LASER BEAMS. Fuck do I hate physorg.

Look at the comments, it's all Jim McCanney electric universe and couch potato wannabe philosopher nonsense. Search physorg a bit - you'll see bullshit like alien crash landings and various other nonsense. And look at all the ads. Dear Lord. No scientist I know will go within 10 feet of that heaping pile.

uh-huh (1)

jav1231 (539129) | more than 8 years ago | (#14758099)

I love it when they come up with these totally original and ambiguous names like "mutlipartite entanglement." Why!? What EVER could that mean? Oh brother...

Re:uh-huh (1)

mikael (484) | more than 8 years ago | (#14758237)

I love it when they come up with these totally original and ambiguous names like "mutlipartite entanglement." Why!? What EVER could that mean? Oh brother...

Perhaps you meant dasterdly-mutleypartite entanglement?

Sounds like one of Klunk's inventions that didn't quite work as expected.

Re:uh-huh (1)

jav1231 (539129) | more than 8 years ago | (#14758491)

LOL! It's like the scientist version of naming your kid "OrangeJello."
I can just see the guy, "We're calling it 'multipartite entanglement!'" And his colleagues going, "Is that a technical term?"

Quantum Encryption (3, Funny)

Absolut187 (816431) | more than 8 years ago | (#14758137)

Hacked before it was even released.
That is worse than the Xbox.

I remember reading about this undefeatable encryption on slashdot a few months ago.
Seriously, that had to be the most short-lived security scheme ever.

Re:Quantum Encryption (1)

Jerry Coffin (824726) | more than 8 years ago | (#14758504)

I remember reading about this undefeatable encryption on slashdot a few months ago. Seriously, that had to be the most short-lived security scheme ever.

Quantum cryptography (more accurately, quantum key distribution) has been around a bit longer than that -- there was an article in the July 1992 issue of Scientific American discussing work Charles Bennet was already doing with it then. A quick search shows there was a short thread about it on Usenet [google.com] shortly after publication (though I'll admit, it probably wouldn't be easy to find unless you already knew what to look for).

That means it's been around for a bit over 13 years (maybe 14), wich is a lot longer than many forms of cryptography last. Of course, it is a bit different since, as mentioned above, quantum "cryptography" isn't really a form of cryptography at all, but that's a whole different question. Perhaps more importantly, quantum cryptography has never really been been much more than a theoretical thing anyway, so from a practical viewpoint, this doesn't mean a whole lot.

To respond to another comment elsethread: this would only mean something about tapping underwater (or wherever) optical cables if they were using quantum key distribution to start with. At least the vast majority aren't, so for them it changes nothing -- tapping into such a cable remains difficult but theoretically possible, just as it's always been. Doing it without being detected is considerably more difficult still, but that's mostly a practical thing, not a theoretical one (i.e. it's practically impossible to put in the tap and get the cable spliced back together before somebody notices the break in communication). Tapping an electrical cable is usually done by putting sensors next to the cable that sense the electrical/magnetic field generated by the transmissions in the cable, so the tap never causes any break in communication at all.

One other thing: the mention of Star Trek-like teleportation in TFA is basically a complete red herring -- the teleportation involved here has essentially nothing to do with anything that would transport significant amounts of matter from one place to another.

This is teleportation about the way a flashlight is -- if I turn on a flashlight and point it straight up, a few of those photons could at least theoretically travel for several light years before they hit something to absorb them -- and yes, at least from the viewpoint of the photons doing the traveling, the travel really is instantaneous. To an external observer, they're traveling at the speed of light, but the time dilation effect means that to them, no time elapses between leaving and arriving.

P.S. For the true pedants: yes, since even space isn't an absolute vacuum, they travel only travel close to the theoretical "speed of light" and some time elapses during the trip -- but drastically less than it looks to us as external observers.

This is great (3, Funny)

CatWrangler (622292) | more than 8 years ago | (#14758159)

Now I can be screwed in 32 different states. Kinda like Madonna.

Re:This is great (1)

ScrewMaster (602015) | more than 8 years ago | (#14758349)

In her case, more like all fifty plus Puerto Rico.

what? (-1, Offtopic)

Anonymous Coward | more than 8 years ago | (#14758172)

50 trillion years ago? Oh ya, I don't need to type..

right... (2, Funny)

smash (1351) | more than 8 years ago | (#14758193)

Back to IP over avian carrier? :)

smash.

Re:right... (1)

marcushnk (90744) | more than 8 years ago | (#14758303)

Yeah.. I want to booby trap the message so that if anyone tries to "clone" the message for stealth decryption... *poof* instant feather cloud :-D

*sigh* (1)

MarkusQ (450076) | more than 8 years ago | (#14758382)


Back to IP over avian carrier? :)

Oh great. As if the botnets and spam and phishing and all the other nonsense aren't enough to drive a simple sysadmin mad, now I'm going to have to wory about bird flu as well?

--MarkusQ

Cloning is immoral! (3, Funny)

noidentity (188756) | more than 8 years ago | (#14758197)

We need to put a stop to this quantum cloning. It is immoral and wrong. Who knows where it might lead!

Re:Cloning is immoral! (1)

skoaldipper (752281) | more than 8 years ago | (#14758314)

Maybe alien civilizations already had this same philosophical discussion and failed; which might very well explain all the dark matter in the Universe.

Re:Cloning is immoral! (1)

scotch (102596) | more than 8 years ago | (#14758436)

No, Human Cloning is fine, it's the human-animal hybrid programs that must stop - they'll be the ruin of us all. Ruin I say, ruiiiiiiiin!!! Won't someone of the children-puppy hybrids?

Great! (1)

mr_zorg (259994) | more than 8 years ago | (#14758201)

Just great. Now we can hack a form of encrypted transmission we don't even have yet...

Hmm, how seredipitous... (5, Interesting)

kopasa (866116) | more than 8 years ago | (#14758213)

It's interesting that we were just talking about this very article (well the actual release, not this article about it) in a analytical mechanics class I'm taking. One of the things that wasn't mentioned in this article was the fact that the beam of light cloned was only done so to about 66% accuracy. I'm sort of kept from going into more details about this by my own fairly limited grasp on the matrix mechanics, but as the clone wasn't perfect, the uncertainty principle was upheld. It is fairly worrisome to see this study spun much out of proportion though. The opening blurb about Captain Kirk only reinforces untrue stereotypes about the potential of quantum teleportation. Alas, if journalists were physicists...

If journalists were physicists... (1, Funny)

Anonymous Coward | more than 8 years ago | (#14758371)

You'd have to read the paper every day because it would be on the test.

Stock charts would be replaced by their formulae.

Articles would be published only after 6 month's peer review.

Articles would be written only after attaining an NSF grant.

The grant would in include USD$4 Billion for a 10-acre superconducting adjective collider (SAC) for smashing random words together in the hope of finding new, short-lived metaphors. Expected completion by 2018.

Re:Hmm, how seredipitous... (1)

eclectro (227083) | more than 8 years ago | (#14758384)

The opening blurb about Captain Kirk only reinforces untrue stereotypes about the potential of quantum teleportation.

That sounds like Captain Kirk's evil twin speaking.

Re:Hmm, how seredipitous... (1)

diqrtvpe (929604) | more than 8 years ago | (#14758465)

If journalists were physicists, we would be teleporting around willy-nilly by now in our flying cars with interstellar capabilities. Of course, then all the freelance physicists embedded in active units would be constantly complaining about the divergence of their field, so it's probably a good thing things are the way they are (sorry, I've been thinking too much about E&M recently, couldn't restrain myself).

Not without detection? (1)

the_brobdingnagian (917699) | more than 8 years ago | (#14758214)

According to the article: "Quantum cryptographic protocols are so secure that they can not only discover tapping but also where and how much information is leaking out. Now, using telecloning, the identity and location of the eavesdropper can be concealed." Does this mean the eavesdropping can still be detected, but no information about the eavesdropper can be obtained?

No-Cloning Theorem (0)

Anonymous Coward | more than 8 years ago | (#14758220)

Somehow I doubt this is cloning without disturbing the original state...

http://en.wikipedia.org/wiki/No-cloning_theorem [wikipedia.org]

Dammit (1)

budgiebottom (920743) | more than 8 years ago | (#14758236)

I just finished compiling Quantum encryption support last week, now I'll have to recompile my kernel. Any word on when the patch will be released? Which repository should I use?

no fundamental rules of QM broken (1)

mrpeebles (853978) | more than 8 years ago | (#14758238)

I haven't read the PRL, but the linked article says:
"Quantum cryptographic protocols are so secure that they can not only discover tapping but also where and how much information is leaking out. Now, using telecloning, the identity and location of the eavesdropper can be concealed."
So as far as I can tell, the parties sending and receiving the message still know that their is an eavesdropper, just not
"their identity and location." I am sure that heisenberg is still fine, a quantum state still cannot be cloned, and information cannot be sent faster than the speed of light. If this was the case, this would be the headline, and I'm guessing it would be on cnn headline news. (Maybe the world isn't that nerdy though... ;-))

Carefull... (1)

turtleAJ (910000) | more than 8 years ago | (#14758247)

I don't know if you guys read this:
http://yro.slashdot.org/comments.pl?sid=177904&cid =14754716 [slashdot.org]

But the MWOCPT also has patents on this field...

Please, our patience is running short... we don't want to shut-off the Moon's Dark Side stabilizing gravity amplifiers... Or you thought the Moon always faced this way becuase of nature???
Arghhh,

-Stitch
LOCATED at MilkyWay.Sol.3 (aka, Planet Earth)
eMail slashstich@yahoo.com

Other news (1)

wetfeetl33t (935949) | more than 8 years ago | (#14758269)

So let me get this straight

There is a security hole in technology that hasn't even been developed yet?
Isn't someone gonna put a patch out for it?

I have a long distance quantuum eavesdropper (2, Funny)

Anonymous Coward | more than 8 years ago | (#14758308)

On average, I'm able to correctly decode 50% of the bits.

In Soviet Russia... (1)

Gravis Zero (934156) | more than 8 years ago | (#14758374)

In Soviet Russia, we don't have first laser.

Quantum Encryption (1)

dilchill (913547) | more than 8 years ago | (#14758399)

This article is NOT about quantum cryptography at all. Telecloning is related to quantum entanglement which is behind basic quantum cryptology, but they are two completely different subjects. Also, we don't even have basic quantum computers yet...I think it will be a long time before we're teleporting people.

I wonder.... (0)

Anonymous Coward | more than 8 years ago | (#14758402)

I wonder if this will make porn faster to get um.....

ScuttleMonkey didn't read TFA, clearly... (1)

YU Nicks NE Way (129084) | more than 8 years ago | (#14758445)

The submission is simply wrong: the article says
"Quantum cryptographic protocols are so secure that they can not only discover tapping but also where and how much information is leaking out. Now, using telecloning, the identity and location of the eavesdropper can be concealed."
, but the summary says "eavesdropping on a quantum encrypted link can now be done without detection", which is exactly the opposite.

Calvin's work? (2, Funny)

rgaginol (950787) | more than 8 years ago | (#14758466)

Are we sure that this story wasn't posted by Calvin as his latest school assignment? If you have a look at the PDF with edits left in, you'll see words like "Transmogrify" crossed out all through it. I'm sure Hobbes could have put him up to it.

Quick summary of quantum theory (2, Funny)

saboola (655522) | more than 8 years ago | (#14758514)

Theorizing that one could time travel within his own lifetime, Dr. Sam Beckett stepped into the Quantum Leap accelerator and vanished .... He woke to find himself trapped in the past, facing mirror images that were not his own and driven by an unknown force to change history for the better. His only guide on this journey is Al, an observer from his own time, who appears in the form of a hologram that only Sam can see and hear. And so Dr. Beckett finds himself leaping from life to life, striving to put right what once went wrong and hoping each time that his next leap will be the leap home.

"Oh boy.."

IIRC (2, Funny)

alx5000 (896642) | more than 8 years ago | (#14758517)

That reminds me of the Windows XP anticopy scheme. Long before it was even released publicly, the crack had already hit the street. Sweet.

Ah, yes! (3, Funny)

sonofagunn (659927) | more than 8 years ago | (#14758531)

I've been quantum telecloning via multipartite entanglement for years with my ultra-flux quasi capacitordangle jimmy-rigged to a quanto-farscope for multi-resolution ohmage. I built this with the latest in Lego technology!

quantum teleportation (0)

Anonymous Coward | more than 8 years ago | (#14758570)

So, when do we send a satellite off into space with a "quantum receiver" on board? We could send it to Pluto (the planet) and have it blow up or do something drastic (you know, for the effect) which would be visible from Earth once it gets back to us at the speed of light.

Missing the point (1)

Belseth (835595) | more than 8 years ago | (#14758665)

It's a quantum party line!
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