Chinese Physicists Achieve Quantum Teleportation Over 60 Miles

MrSeb writes "Chinese physicists are reporting that they've successfully teleported photonic qubits (quantum bits) over a distance of 97 kilometers (60mi). This means that quantum data has been transmitted from one point to another, without passing through the intervening space. It's important to note that the Chinese researchers haven't actually made a photon disappear and reappear 97 kilometers away; rather, they've used quantum entanglement to recreate the same qubit in a new location, with the same subatomic properties as the original qubit. The previous record for transmitting entangled qubits was 16 kilometers, performed by another Chinese team back in 2010 — and perhaps most excitingly, the researchers seem confident that their system will scale up from 97km to distances capable of reaching orbital satellites, at which point we'll actually be able to build a global quantum network for all of our cryptographic needs."

Comments

That's nothing

[crazyjj]

I hear the next step is transporting economic superpower status over 7,000 miles.

Re:That's nothing

[Immostlyharmless]

Old News, it's already been done :P

Re:That's nothing

[cpu6502]

Reminds me of an Outer Limits episode.

They "transport" people through something similar to quantum entanglement that allows them to pass the data of Person #1 across several lightyears, and use that data to artificially create Person #1 at the new location. Of course that means they have two identical people, so they have to kill the original.

Re:That's nothing

[YodasEvilTwin]

I hold out hope that this will be possible in the very distant future, but there's a few giant problems to overcome: (1) Syncing trillions of atoms at the same time (2) Having the raw materials and movining them into place (3) Being able to determine the state of trillions of atoms at the same time.

Re:That's nothing

[crazyjj]

"Think Like a Dinosaur", based on the excellent short story by James Patrick Kelly. One of the best episodes of that series.

Re:That's nothing

[19thNervousBreakdown]

If only we'd finished our ladder to Heaven first.

Re:That's nothing

[gbear711]

Yeah, our grandchildren s confiscated cash wasn't good enough.

Re:That's nothing

[Dr Herbert West]

I saw that episode, it was one of the better shows from the "new" series (not the black and white series from the 60s)

Re:That's nothing

[Anonymous Coward]

"Balancing the equation"

Re:That's nothing

[BitHive]

When the arsonists live in the same building as you, putting out the fire may not be fair but neither is letting it all burn.

Re:That's nothing

[thelovebus]

Of course that means they have two identical people, so they have to kill the original.

Discussion of this sort of thing always reminds me of this great cartoon.

Re:That's nothing

[kaehler]

>>>Barack Obama is already "punished" the banks who stole your money--with bailouts, jobs in his cabinet, and sweetheart deals that absolve them of mortgage fraud. That'll teach 'em!

Jobs in the cabinet - yes
Bailout - that was Bush

Re:That's nothing

[lgw]

Sure, but we know everything bad was Bushes fault. Obviously the interesting question becomes who else besides Bush caused any given bad thing. And only a small percentage of the bank bailouts happened before Obama took charge. So, stipulated, all Bushes fault, but given Bush isn't running for President right now, the interesting bit is: also Obama's fault.

Re:That's nothing

[lgw]

Wow, I've never seen a n argument that NAFTA caused all our jobs to go to the Chinese before. So, please do explain in your racist way why you deserve a job more than a man in China (ignoring of course the fact that most of the manufacturing jobs are lost to robots, not to China).

Meanwhile, manufacturing continues to rise in America, as it always has. It's just that stuff gets made by robots now. No one mindlessly toiling in repetitive work? What horror!

Re:That's nothing

[steelfood]

Why they would want to send it back would be completely baffling.

Re:That's nothing

[cheesybagel]

Are they still counting as US manufacturing something made by US companies (even if their headquarters is in the Cayman Islands) abroad (e.g. China) or what?

Re:That's nothing

[Hamsterdan]

Was that episode "Thinking like a dinosaur" ?

Re:That's nothing

[csumpi]

Nah, that's already in progress.

And looking at your signature, with your support. Maybe that's why your post was modded funny.

Re:That's nothing

[rockout]

I think his point was that your insistence on "counting" it as US-made or not is has become irrelevant.

Re:That's nothing

[Carewolf]

This is why I find teleportation scary. There is no way anyone is going to send the matter along for the ride, I think they are just lying in Star Trek. Even if they do, they are essentially killing you and then creating a clone out of your cremation dust.

Re:That's nothing

[Anonymous Coward]

Even if they do, they are essentially killing you and then creating a clone out of your cremation dust.

Stargate, scary. Goaul'd rings, scary. Nightcrawler teleportation, not so much. At least until he actually slows down to see the nightmare fuel on the other side.

Re:That's nothing

[cpu6502]

>>>Bailout - that was Bush

You forgot that stimulus bill which passed during Obama's first month, and included bailouts not just for GM and other corporations, but additional funds for the banks too.

Re:That's nothing

[lgw]

No - the amount of stuff actually manufactured in the US has been flat or rising in recent times (not sure it has ever fallen). It's the number of manufacturing jobs that has fallen. That disparity is caused by automation (and I have a hard time accepting an economy where all basic needs are mat by automated manufacturing as some kind of dystopian horror). China has recently had net loss of manufacturing jobs too, which is why is economy is a bit ... hollow right now.

That's what technology is: the ability to make stuff more efficiently.

Lord?

[i.r.id10t]

Lord... Whats a qubit?

Re:Lord?

[Jose]

Lord... Whats a qubit?

it is more of who than a what...Qubit is Q*Bert's Chinese cousin.

Re:Lord?

[Anne_Nonymous]

It's a new method for transmitting spam.

Re:Lord?

[rubycodez]

Most Chinese cut their queue off these days

Re:Lord?

[osu-neko]

Lord... Whats a qubit?

How long can you tread water? :p

Re:Lord?

[Anonymous Coward]

Let's see a cubit, I used to know what a cubit was.

Well don't worry about that just go out and collect all those animals by twos male and female and put them into the ark

Riiight.

Re:Lord?

[Anonymous Coward]

jeez, I wanted to reply to this with the word "right..." which as you know the correct response - but ran afoul of the ascii art filter - wtf? killjoy.

Re:Lord?

[bigredradio]

I was wondering if anyone else got the joke. Happened to listen to that album (vinyl) last weekend with my kids. Unfortunately, most of that skit was lost since I had to explain who Noah was. They have not been privy/subjected to Sunday school like I was.

Re:Lord?

[Anonymous Coward]

Lets see a cubit...I used to know what a qubit was
Well don't worry about that Noah
When you get that done
Go out into the world and
Collect all of the animals in the world by twos
Male and female, and put them into the ark

Re:Lord?

[Qubit]

Lord... Whats a qubit?

Here! I'm here... finally. I would have gotten here sooner if the Chinese hadn't been, you know, teleporting me around all morning.

*stretches*

Hmm... well that sucks. I think they made a mistake and put one of my quarks in upside down -- I feel strange all over now.

Re:Lord?

[Beaker74]

Right!

Who is this, really? :) Love that album.

Re:Lord?

[_0xd0ad]

Bill Cosby

Re:Lord?

[Anonymous Coward]

I bereive you'le thinking of Q*Belt. Faget.

Re:Lord?

[Anonymous Coward]

QBIT is a quantum bit.

One bit is just YES or NOT. A Quantum bit is MAY be YES or NOT (remember the schordinger paradox)

The final state is decided by a Quantum algorithm (a solution) So a group of QBITS is a Quantum message.
Bob and Alice, will shown the message only when the quantum cryptographic mechanism is enabled.

For free you can have higger speeds (Einstein-Podolsky-Rosen paradox) than normal light speed. This is called 'teleportation'
 

Re:Lord?

[Anonymous Coward]

Funny, I thought you'd find teleportation charming.

Re:Lord?

[StillNeedMoreCoffee]

I got it. We do broadcast our age. I remember when it came out.

      You and me lord.

Re:Lord?

[FrootLoops]

Here's a summary of the physics, including what a qubit is.

Quantum states
Suppose some process produces two electrons. It happens that a particular measurement of a quantum property named spin always comes out as +1/2 or -1/2 for electrons. Now suppose the process that created the electrons must obey a conservation law which forces the sum of the spins of the two electrons to be 0--say the particles that interacted to make the electrons themselves had 0 spin. One electron must then be spin +1/2 and the other must be -1/2. However, until the measurement is performed, you have no idea which is which. More is true: a fundamental part of quantum mechanics is that particle properties can be in multiple states simultaneously right up until a measurement is performed, at which point the property collapses to a single definite value which is randomly chosen based on the relative fractions (actually amplitudes) of the states it used to be in. Thus you can perform a quantum mechanical experiment exactly the same twice without getting the same outcome both times, though you can at least calculate the outcome probabilities. A qubit is simply the state of an electron's spin property before a measurement is made, which in general can be a mix of +1/2 and -1/2. This generalizes to other particles and other two-state properties. (More technically a qubit is an element of a 2-dimensional Hilbert space acting as the state space of some quantum property.)

Entanglement
Right after being produced, the two electrons are each in both the +1/2 and -1/2 states. They are "entagled", because if you measure the spin of one electron, from the conservation law you know what a measurement of the other electron's spin must be. Entanglement is actually a very simple consequence of the fact that quantum properties can be in multiple states simultaneously yet conservation laws still need to hold. It's an interesting exercise to try and get faster-than-light communication from this setup, though you'll be unable to. If you're familiar with the relativity of simultaneity, try to both blow up the earth and not by some set of decisions based on the entangled particles' measurements.

Quantum teleportation
Using a setup I will not discuss in detail, person A has a qubit encoded in the spin of an electron, and she wants to send the qubit to person B--that is, she wants person B to have an electron with the same spin property in all its mixed-up multiple-states-at-once glory. The setup requires a classical communication channel and some extra entangled particles. Using it, person A can instruct person B to prepare an electron with the same spin state as person A started with. It happens that person A's qubit is destroyed in the process, so the information "teleports", though note that it jumps from one particle to another. The information is all that's teleported, not the particle, and it's not teleported faster-than-light because of the classical communication needed.

Re:Lord?

[Anonymous Coward]

Ri-i-i-i-i-ght!

Am I on Candid Camera?

Re:Lord?

[smi.james.th]

I don't understand what's actually news here. TFA doesn't seem to mention anything about classical communication channels, but if they were used then why is the 60 mile figure significant? Could one not then transport the qubit over an arbitrary distance?

Re:Lord?

[symbolset]

The prior distance was 9 miles. They beat that distance by 51 miles. Besting the competition by 6x is grand, but that's not the big deal. 60 miles is far enough distance to measure whether the communication is "instantaneous" within or without the frame of general relativity. Properly refined this may be the Star Trek "subspace communication" and further refinements might open up a whole new understanding of physics. The prior distance was not enough for proofs of this nature because of the difficulty of measuring such fine increments of time against the uncertainties of the method.

Is that a big enough deal for you to accept it's a worthy post for "news for nerds"?

Re:Lord?

[Anonymous Coward]

I was with you right up until "Suppose some process produces two electrons. ".

Re:Lord?

[FrootLoops]

One of the articles does mention, "For quantum encryption [teleportation] to work, though, we need to be able to transmit entangled photons over a long distance". They do ignore the classical information channel, but probably because transmitting entangled photons is far more difficult and doing so basically solves the classical communication channel problem.

About teleporting over arbitrary distances, you need to get an entangled particle from person A to person B without it interacting with anything else, and it's difficult to prevent the particle from interacting with something on the way there. They're trying to reach distances that allow a satellite network to successively teleport quantum information in hopes of providing an almost perfectly secure communication channel, probably for key exchanges since the bandwidth will be quite low for a long time.

Re:Lord?

[FrootLoops]

I don't agree; where did you get that information? I imagine essentially no physicists believe that faster-than-light communication will be discovered using something as well-understood as quantum teleportation. It's not as if theory predicts FTL communication with this setup--it doesn't. FTL communication would indeed be epoch-making which is why the recent FTL neutrinos were such a big deal, but even there all the physicists I heard from didn't actually believe the result was real, and indeed it was not.

Re:Lord?

[Anonymous Coward]

whoa...

Re:Lord?

[Anonymous Coward]

How long can you tread water?

Re:Lord?

[i.r.id10t]

It woulda helped had my less-than voice type=cosby greater-than tags hadn't been eaten....

But I'm glad at least one other old fart got it :)

Satellites??

[Anonymous Coward]

Why would you involve satellites?

It is teleportation, so line-of-sight is not involved in this... Right?

Re:Satellites??

[GameboyRMH]

You can't transmit meaningful information with quantum teleportation alone, you still need a classical channel that operates by conventional means unless you want to transmit uncontrollable random garbage.

Re:Satellites??

[_0xd0ad]

The information contained in the qbit is transported from one entangled photon to another, but you first must get that entangled photon to the destination via more conventional means. They're doing that with a laser.

Re:Satellites??

[rwven]

Well, it's probably so spy photography could be securely transmitted from a satellite to earth. Other than that....excellent point. Could be transmitted straight "through" earth....except the part where it wouldn't actually be going THROUGH the earth.

Re:Satellites??

[Anonymous Coward]

unless you want to transmit uncontrollable random garbage.

So that means the satellite television providers will be all over this.

Re:Satellites??

[Beryllium Sphere(tm)]

"Teleportation" would be for key creation and distribution.

Re:Satellites??

[Anonymous Coward]

You can't transmit meaningful information with quantum teleportation alone, you still need a classical channel that operates by CONVENTIONAL means unless you want to transmit uncontrollable random garbage.

why does it have to be "conventional"
Something conventional hundreds of years ago was lighting your house with fire or candles. now we have light bulbs.
At the time electricity was totally unconventional, now our society couldnt live without it.
Think outside the box, and it might just happen

Re:Satellites??

[GameboyRMH]

And yet all those lighting sources and electricity all operate at exactly c, which our current understanding of physics says cannot be exceeded...unless you're a theoretical physicist you think inside this box.

Re:Satellites??

[FrangoAssado]

That's not really true. The real motive is explained in this other comment.

That said, I think that what you mean is (and this is true): to perform quantum teleportation, you still need a classical channel. But the reason for the satellites in this case is not that: the satellite is being used to send entangled photons (i.e., it's a quantum channel). The classical information could have been sent in any other way (over the Internet, for example), but to send entangled photons, there must be no measurements of the photon along the way.

Re:Satellites??

[AchilleTalon]

As well as chinese restaurants.

Re:Satellites??

[Zordak]

Still, it makes for an interesting though experiment. If you could completely characterize a larger object and transmit that signature at c to another point, then you could effectively permit matter to travel at c. Of course, you could only go somewhere there was a receiver, so it would have to be somewhere we've already gone the old fashioned way. But it could make for a very efficient way to move stuff around in our own solar system.

Re:Satellites??

[Zaphod The 42nd]

Lol, you've completely misunderstood. He doesn't mean "conventional" like, traditional. He means "Classical Information", which is contrasted with "Quantum Information".

Everything you've ever considered "information" is really in the subset "Classical Information" . That classical information has to be transferred somehow, and we have several means to do so; the so-called "conventional" methods of transport. This new method of quantum teleportation is un-conventional. Sadly, quantum teleportation CANNOT transmit Classical Information; by the laws of physics. So you HAVE to use, by definition, a conventional method to transfer classical information.

Re:Satellites??

[Anonymous Coward]

Except...this would require interpreting all of those bits from the one giant burst of information. You're still limited to the bandwidth of your close-to-c channel.

Re:Satellites??

[symbolset]

I do believe that the current research is that the qbits can be entangled and separated at subluminal speeds. But operations that can impact the state of the qbit like observation, at what speed does that propagate to the entangled qbit? We don't know. It might be instantaneous no matter how far apart the qbits are, irrespective of general relativity's lightspeed limit. To discover the speed of propagation of this information we must separate the entangled qbits by enough distance to measure the propagation of the change with certainty within the confidence level of our measuring equipment. So this research is important, and increasing the distance is important. It may be that changes to one entangled qbit propagate to the other at subluminal speeds, but maybe not.

The potential that is proposed isn't instantaneous communication with anywhere, but the potential that - if we can store unmanipulated entangled qbits - instantaneous communication with the qbits we've stored and separated at subluminal speed can be achieved. It's a big deal. If this is possible we'll find a way to store nigh-infinite entangled qbits and send them far.

Re:Satellites??

[Dabido]

'... unless you want to transmit uncontrollable random garbage.'

So, at the moment it's a bit like what we see on television! :-)

Ender would be thrilled.

[rwven]

So....how long until we have an Ansible?

Re:Ender would be thrilled.

[Githaron]

Just before Jane comes into existence due to the Hive Queen attempt to communicate with the humans.

Re:Ender would be thrilled.

[zAPPzAPP]

You did notice from the summary how this involves sending photons by laser?

Re:Ender would be thrilled.

[Baloroth]

This, and all other quantum "teleportation" and related entanglement phenomenon, do not allow for faster-than-light communication. The important thing to note is that the qubit is "teleported", not the photon itself: the photons are transmitted conventionally via some means (in this case, it looks like they did it through open air). Since the photons are entangled with a photon you retain, measuring one collapses the wave-function of the other and allows both parties to know what the state is simultaneously. The security ramifications are that any eavesdropper will collapse the wave-function before the receiver gets the photon, so he will not receive the photon in the same state as the receiver sent it.

You cannot, according to what we know of physics, use quantum entanglement to send information faster than light.

Re:Ender would be thrilled.

[bolthole]

If so then the summary of "without crossing the intervening distance" is a lie. The information was encoded and de-encoded for transit,but it still "travelled". No teleportation here, move along, move alone.

Re:Ender would be thrilled.

[Anonymous Coward]

Alternatively, the information was simply *discovered* at both ends, and found to be in agreement when both points communicated subluminally afterwards.

This only works with a many-worlds interpretation of QM, though - there can't be a single hidden varible (says Bell's theorem).

Re:Ender would be thrilled.

[rwven]

Grrrr. Foiled again!

Re:Ender would be thrilled.

[FrangoAssado]

It's actually worse than that. You could send the photons ahead of time (i.e., you could stock photons and use them to perform teleportation whenever you need it), but teleportation is still not "instantaneous".

The problem is that, to perform the teleportation, you must first measure the source, and then send the result of the measurement to the destination (that's just 2 bits of classical information). Given this information, the person in the destination chooses one of four measurements to perform in the corresponding destination photon, and then the teleportation is complete. Wikipedia has a more detailed explanation, including the measurements performed.

Re:Ender would be thrilled.

[bdenton42]

You cannot, according to what we know of physics, use quantum entanglement to send information faster than light.

But would it be faster sending information from one side of the Earth to the other than satellites or undersea fiber? If so financial institutions will be all over this.

Re:Ender would be thrilled.

[fadethepolice]

You seem very sure of this. I am unsure. Since time is not a constant then almost anything is possible with regards to causality. Relative causality? http://arstechnica.com/science/2012/04/decision-to-entangle-effects-results-of-measurements-taken-beforehand/ I would bet hard money you could run an experiment similar to this but instead send the information forward in time, faster than light. If you transported one of a pair of more stable molecules that were entangled then constantly manipulated there states wouldn't that information travel faster than light even though the particles themselves cannot travel from place to place faster than light? Also, if you took a stable wormhole and transported one end at the speed of light for an extended period of time. Then sent something through one side of the wormhole to another you could theoretically instantly skip the time betwen, allowing for either faster than light travel, or travel back in time.

Re:Ender would be thrilled.

[Baloroth]

I'm going to say that I believe FTL communication may be possible (in fact, I hope it is). The problem is it violates a significant foundation of modern physics: to wit, relativity, and I'm not exactly prepared to throw out relativity. You can't just manipulate entangled particles in an arbitrary fashion and have them stay entangled. Making a change to one (a controlled change, mind: one that is actually random could still preserve entanglement) collapses the entanglement between the particles, precisely by you knowing what the change is. The wormhole question is interesting, because ultimately you aren't actually traveling faster than light, you just take a back-route, so to speak. However, it requires spacetime to have a certain arrangement and properties which is, at this point, only theoretical (i.e. we have no idea if wormholes are actually possible.

The thing about quantum entanglement is that while it is weird, and not expected by relativity, it still seems almost to strive (insofar as natural laws can do so) to behave according to the limits of relativity on FTL travel, which makes sense, since the laws of nature must be consistent. The question is ultimately if there is a higher law than relativity to appeal to that allows FTL travel. It really doesn't seem likely, but then again neither did quantum entanglement 200 years ago.

Re:Ender would be thrilled.

[FrootLoops]

You'd have to beam particles through the earth to do what you suggest (not currently practical), at which point you might as well use classical methods.

Re:Ender would be thrilled.

[Anonymous Coward]

If you transported one of a pair of more stable molecules that were entangled then constantly manipulated there states wouldn't that information travel faster than light even though the particles themselves cannot travel from place to place faster than light?

Messing with one part of an entangled pair will only change the state of the other half in such a way that you can't tell anything has changed from just looking at the second part alone. In other words, if you had half of an entangled pair, and measured it, you would see the same distribution/probabilities of different outcomes regardless of what the other end does. It is only later, when the other end tells you what they measured, that you can see there is a correlation between the two measurements.

Also, if you took a stable wormhole and transported one end at the speed of light for an extended period of time.

This requires that stable wormholes are possible. This unknown at the moment, and it can easily end up that they are not possible.

Re:Ender would be thrilled.

[Zaphod The 42nd]

I want Ansibles really badly too, but Quantum Teleportation by definition cannot transmit classical information. Ever. Its a pipedream (and one which would violate causality and locality out the wazoo).

The only thing you can quantum teleport is quantum information, which is next to useless for anything except a special kind of cryptography
(which is actually useful. But thats all).

Re:Ender would be thrilled.

[Zaphod The 42nd]

You're massively oversimplifying. They ARE transmitting information at faster-than-light speed, but only quantum information. Also, in order to verify it, you have to transmit a couple bits of classical information as well, which must cross the intervening distance. No part of quantum teleportation will violate locality or causality, and you should know that by now. It still teleports, its your fault for misunderstanding what that implies.

Re:Ender would be thrilled.

[StillNeedMoreCoffee]

I'd just run a fiber cable through Hollow Earth.

Re:Ender would be thrilled.

[Zaphod The 42nd]

Nope, nope nope nope, a million times wrong. Sorry buddy, I like believing that quantum physics is magic that lets us break all the rules too, but thats just silly. We know better. If you're going to try to understand it, really read up on it, don't just form opinions and ideas from hearsay. As you yourself said, he is very sure of himself, but you are very unsure. You don't know what you're talking about.

Quantum mechanics cannot violate causality or locality, and cannot, by law, transmit classical information at faster-than-light speed.

I tried to find the site I read awhile ago that explained it all in depth, but google failed me, sorry. Read around, there's no point in me trying to write pages of explanation about a very complicated subject on a /. post.

You're misunderstanding how that experiment works. Its very, very complicated, and took me a long time to understand too, so don't feel bad. But it isn't that you're later making a choice which effects that past; that IS NOT POSSIBLE. Instead, it is merely that you are filtering out which photons would have taken one path or the other by knowing which path they take. Photons exist which are constantly part of the interference pattern and not part of the pattern. We are merely choosing to filter out certain photons at a time.

Re:Ender would be thrilled.

[Anonymous Coward]

>forward in time, faster than light

I'll take you up on your bet since, as far as every observation ever made says, this is not possible.

> then constantly manipulated there states

Entanglement breaks once you measure the state.

The best way to think of quantum entanglement and information transfer is, think of your entangled entities as two coins. When you entangle them, you make an interesting requirement that one always has to be the opposite of the other, but to do this, you had to spin them and seal them in two boxes. Now, your two entangled coins are constantly spinning in their boxes. You can take these boxes wherever you like, but any time one of you opens them, both coins will stop spinning (the person with the unoppened box has know way of knowing), and one will be opposite the other. When either of you opens the box, the chances of you getting a heads or tails is *exactly* 50/50. So, lets entangle a bunch of coins in some boxes and go our separate ways. I go to my house, open a few boxes. Get some random heads and tails. You open your boxes, and you get a bunch of random heads and tails. There's no information transfer. The only way we can relate our heads and tails is to call each other up on a phone.

This is the same with that paper you linked. The title is horribly wrong. The results were there, but by back projection, as in, they went through the steps, measured the results, and found that yeah, knowing the final states, we can go backwords and say, they were entangled at these earlier points. Causality is safe.

Re:Ender would be thrilled.

[FunkDup]

measuring one collapses the wave-function of the other and allows both parties to know what the state is simultaneously

seems like a great argument against eavesdropping, but I'm not seeing how it's an argument against FTL communication.

Re:Ender would be thrilled.

[marcosdumay]

No, teleportation is instantaneous. It happens when the first peer does one of the measurements (don't just ask what "first" means here - I have no idea and it seems I'm not alone). All the rest of the procedure is there just to set the experimental conditions.

Re:Ender would be thrilled.

[FrangoAssado]

No, see the intermediate states in the step-by-step walkthrough of quantum teleportation in Wikipedia. Immediately after the first peer (called "Alice" in Wikipedia) does the measurement, the destination qubit (called "Bob's qubit" in Wikipedia) is in one of 4 the states described after the paragraph that begins with "Notice all we have done so far (...)". The state of Bob's qubit is represented to the right of the tensor product sign (the circle with the cross inside, for those not familiar with this notation). The states are completely different -- in fact some of them are orthogonal (the first is orthogonal to the last and the second is orthogonal to the third; that's easy to see because alpha*beta-alpha*beta=0).

What this means is that, if Bob doesn't use Alice's result to perform the right measurement in his qubit, he might as well have a random qubit. That's not surprising, since entanglement can't be used to transmit information. It's only with the information from Alice's measurement that Bob can select the right measurement to perform in his qubit to put it in the desired state (i.e., the state "teleported" from Alice's initial qubit).

Re:Ender would be thrilled.

[MaskedSlacker]

I would bet hard money you could run an experiment similar to this but instead send the information forward in time, faster than light.

And those of us who actually know what we're talking about would be happy to take your money.

If you transported one of a pair of more stable molecules that were entangled then constantly manipulated there states wouldn't that information travel faster than light even though the particles themselves cannot travel from place to place faster than light?

In a word: no. The particles would not remain entangled.

Also, if you took a stable wormhole and transported one end at the speed of light for an extended period of time. Then sent something through one side of the wormhole to another you could theoretically instantly skip the time betwen, allowing for either faster than light travel, or travel back in time.

Also no. That's not how wormholes (theoretically) work. They do not 'skip' time in between. They are alternate continuous routes through space and time.

The idea that relativity allows for violating causality is laughable. Relativity ASSUMES causality. Without causality, General Relativity would fall apart.

Ansible?

[mspring]

Is this finally the ansible?

Re:Ansible?

[Anonymous Coward]

Sigh. What happened to the days when nerds would read science fiction without believing that someday it would all be real?

Re:Ansible?

[Eponymous Hero]

yeah like those guys who went to the moon. what a bunch of assholes!

Re:Ansible?

[rubycodez]

Too much has become real from science fiction, and it's scary. One little ferinstance, Jules Verne had "electric bullets" that were mocked for over a century, of course you couldn't put enough charge into a projectile to make a foe fall "as if struck by a thunderbolt", right? http://electronics.howstuffworks.com/gadgets/other-gadgets/taser-shotgun-shell1.htm

Re:Ansible?

[spiffmastercow]

Sigh. What happened to the days when nerds would read science fiction without believing that someday it would all be real?

When was that? My dad still complains about not having a flying car or being able to take a flight to the moon.

Re:Ansible?

[Intrepid imaginaut]

or being able to take a flight to the moon.

Yes yes, working on it, give us about nine years.

Re:Ansible?

[Anonymous Coward]

'...or being able to take a flight to the moon.'

"Yes yes, working on it, give us about nine years."

Newt, is that you?

Take THAT, Mr Mpaa Riaa!

[h00manist]

Now we won't transfer our warez over any wires or IP numbers at all, and will just teleport the data all over the place.

So it's replication

[HalAtWork]

So it's replication, not teleportation?

Re:So it's replication

[Anonymous Coward]

just like Star Trek transporters.

Re:So it's replication

[tstrunk]

So it's replication, not teleportation?

It's not replication, the quantum state of one photon is transfered from one photon to another.
Here's an easy explanation. http://www.youtube.com/watch?v=_qmSdC7aQpY

Replication will never be possible as a quantum state cannot be copied: http://en.wikipedia.org/wiki/No-cloning_theorem

Re:So it's replication

[interval1066]

Is making an exact copy, I mean EXACT, same quantum properties, same everything, mere replication? I think it goes beyond photocopying. Here's a question; so if its a good (the best) copy of something, does that we might be able to replicate objects ad infinitum? Could some mad asshole make a million Brittany Spears? I quake with fear...

Re:So it's replication

[Anonymous Coward]

It's PIRACY!

Re:So it's replication

[Zaphod The 42nd]

No, its quantum teleportation. Quit trying to simplify this, it isn't simple. If you try to simplify it so much, try to find a common metaphor in classical physics, it isn't going to work. You're going to miss a detail and make an assumption. The only thing that this is, is quantum teleportation. It isn't teleportation. It isn't replication.

Quantum Teleportation is very different from Teleportation.

Re:So it's replication

[marcosdumay]

The quantum state is not transfered.

At first both photons are in a mixed stated that make them anti-correlate perfectly. Then, somebody does a measurement and changes the state of one of the photons (to a classical state), as the other photon is perfectly anti-correlated, it changes to the oposite classical state.

Re:So it's replication

[FrootLoops]

No, you're confusing entanglement and teleportation, and I'm not sure if your understanding of "mixed state" is correct. In entanglement the results of measurements of properties on several particles are correlated. In quantum teleportation, the wavefunction of one particle's property is moved to another particle, which happens to collapse the original wavefunction. The result of a measurement on a teleported property is not at all certain, which is really the point. A mixed state is a superposition of pure states, whereas an entangled state causes measurements on multiple particles to correlate somehow in a sense one can make precise using tensor products and separability.

Great Qubit Wall Of China

[localman57]

In other news, another group of Chinese Scientists have announced that they have developed a method for filtering teleported qubits which contain information or ideas which are detrimental to the keeping of order of the society.

Sweet!

[Anonymous Coward]

Instant Chinese Takeout!

This is not just China's Achievement

[l0ungeb0y]

This is part of an international research effort, including schools like Carnegie-Mellon in the US. However, due to the lower costs of photonic qubits in China, it only makes sense to have the majority of experiments carried out over there.

So...

[Anonymous Coward]

Basically we've developed quantom faxing? Is there still an annoying dial tone?

Re:So...

[Anonymous Coward]

"quantum..." typo >.

Seriously

[Anonymous Coward]

What the fuck is being talked about here?

Re:Seriously

[ColdWetDog]

What the fuck is being talked about here?

If that's the entirety of discourse you bring to the site, you just might as well go back to 4chan with the rest of the invertebrates.

(Self-replying, I apologize)

[_0xd0ad]

Note that it's still limited by the speed of light. The key feature, however, is that it is secure: someone intercepting the photon can't copy or read its qbit state without breaking the quantum entanglement, or preventing it from reaching the destination. In either case, the receiver will immediately know that the channel has been broken. It then stops transmitting a response to the sender, and the sender perceives this as also a break in secure communications and stops transmitting. Both the sender and the receiver would then go into failure mode and send query/response polls periodically. When secure communications are re-established, they can resume transmitting data.

Re:(Self-replying, I apologize)

[History's Coming To]

So if you could somehow generate entangled matter ahead of time and move it en masse, say a gramme on the ground and a gramme in the satellite, would that allow FTL information transfer? I'm guessing it can't for obvious reasons, but I can't work out why not.

Re:(Self-replying, I apologize)

[StillNeedMoreCoffee]

So I can see the popularity of quantum DOS attacks on the increase. Maybe you can't know what they are trying to send but you sure as hell can stop them from sending. A limited form of communication at best.

Re:(Self-replying, I apologize)

[0x537461746943]

You are of course correct. The naming of this is very misleading to everyone that hears it for the first time (and probably 100 times after that). The data is encoded on one side. You keep one local. You send the other entangled half to another remote spot and then read them both. This should be referenced as quantum encoding or quantum entanglement only and not have the name teleportation at all in it when discussing the process.

Re:(Self-replying, I apologize)

[Anonymous Coward]

No, because to complete a quantum teleportation the receiver needs to perform operations on their half of the entangled pair which depend on the results of a joint measurement the sender has made on *their* half of the pair and the qubit to be transmitted. The receiver doesn't receive any quantum information until they receive the (classical) information about the measurement result, and that has to be transmitted in the usual way i.e. not FTL.

Re:(Self-replying, I apologize)

[spazdor]

The information contained in those two grammes of entangled matter, isn't information that you've encoded into it. It's information which begins "existing", so to speak, when an observation is made from one end or the other.

Hire a guy to randomly generate 65,536 sequential binary bits, written on paper, duplicated once, and then sealed in 2 envelopes. Shoot him in the face when you're done with him, to rule out information leaks. Now mail one envelope across the world to China, bearing a "don't open until x-mas" label.

Now wait until christmas eve, then go into your 4chan folder and find your favourite 8 kB jpeg of some anonymous boobs. Open up your envelope, take that image file and, bit by bit, XOR it with the bitstream on your sheaf of paper. The resulting ciphertext is indistinguishable from random data - that is, its Shannon entropy is approximately equal to its length. Now you can call up your new Chinese penpal on the phone, read them your ciphertext, and show them some boobs which only they can decode.

It's foolproof, except for the fact that it's pretty easy to open a postal envelope, read its contents, and re-seal it.

Essentially what's happened here is researchers have figured out how to use particles as envelopes, which have much better sealing properties.

Re:(Self-replying, I apologize)

[marcosdumay]

Except that it is not that secure. Quantum encryption can only be secure if you have an authenticated channel to exchange the reading orientations. If somebody can impersonate your peer at that exchange, you are owned.

Re:(Self-replying, I apologize)

[History's Coming To]

So it's only good for key exchange, with a boob analogy. Brilliant :)

Re:(Self-replying, I apologize)

[dotancohen]

Mods! I wasted all my mod points on blow and hookers, please give parent post the attention that it deserves!

Re:(Self-replying, I apologize)

[_0xd0ad]

If somebody can impersonate your peer at that exchange, you are owned.

It would get them nowhere, on its own. They would also need to intercept the entangled photon, without detection - which can't be done (in theory); that photon would simply be ignored, not used for the encryption.

It's basically like you're doing XOR encryption with a random one-time pad, known only to you and your target. The quantum encryption is basically the part that ensures that only you and your target can possibly know what the one-time pad contains (according to present interpretation of the laws of physics). Because any time your eavesdropper intercepts a single bit of the one-time pad, both of you are able to sense this and simply not use that bit.

Turn in your nerd badges

[BitHive]

Queue starry-eyed 500 posts about Ender's game by people whose idea of being a nerd is playing WoW while they wait for "the singularity", FTL communications, and REAL perpetual motion machines.

Re:Turn in your nerd badges

[Zaphod The 42nd]

Its sad, how even among /. you find so many people clearly believing lots of blatant misconceptions about quantum physics. :/
I mean, shit is definitely complicated, took me awhile to wrap my head around. But don't make assumptions or draw conclusions until you understand something, is that so hard?

Chinese cryptography

[magarity]

at which point we'll actually be able to build a global quantum network for all of our cryptographic needs."

If you think things are bad in Europe with the cameras everywhere and in the USA with the Patriot act and whatnot, you'll find out how good you have it when China is in charge of your cryptographic needs.

More accurate title

[Anonymous Coward]

Chinese scientists continue to make shit up, as always: http://www.economist.com/blogs/asiaview/2010/07/academic_fraud_china

a butterfly flaps its wings in China...

[notgm]

and half a world away, another butterfly does too.

not nearly as exciting. boo, science!

Trillions?

[colinrichardday]

If we have a 72-kg (158 lb.) person made mostly out of water, that's about 4,000 moles, or 2.4x10^27 molecules, which is about 7.2x10^27 atoms. The actual number might be different, but it's way more than a trillion.

Re:Trillions?

[Anonymous Coward]

I wonder if the quantum states could be generalized for much of the mass. Does each water molecule need to be in the same state? Does each molecule of tissue need to be in the same quantum state?

It may be possible to narrow it down to just the central nervous system, and then possibly all the way down to just portions of the brain. Narrowing it down to just a couple hundred trillion atoms would be amazing.

While this would create a second (nearly) identical person at the other end, I don't see why you "have to" kill the original.

The next big obstacle is assembly. It's not like you can just throw all that data into a Makerbot.

Re:Trillions?

[Calydor]

It's not like you can just throw all that data into a Makerbot.

GameMaker, on the other hand ...

How do you suggest making the machinery figure out what needs to be exact duplicates, and what can be defaults? For instance, I'd really hate for it to confuse half my brain matter with generic body fat just because I was asleep or something.

Re:Trillions?

[colinrichardday]

An average brain is what, 1.4 kg? Even a tenth of it would be 0.14 kg. This is about 1/500th of 72 kg, so you would still have about 4.8x10^24 molecules.

Re:Trillions?

[Anonymous Coward]

That would be about 2.7 quadrilliards, if you use the socalled "long format" with Million (10^6) Milliard (10^9) Billion (10^12) Billiard (10^15) Trillion (10^18) Trilliard (10^21) Quadrillion (10^24) Quadrilliard (10^27).

The "short form" is used in USA and Brittain, where you go Million (10^6), Billion (10^9), Trillion(10^12) and so forth.

Just for some annoyingly useless information ;)

Re:Trillions?

[tolkienfan]

Actually, merely the process of quantum teleportation destroys the original state, and can only recreate the state once (at most).

CHINA'S cryptographic needs

[xxxJonBoyxxx]

>> ...their system will scale up...to distances capable of reaching orbital satellites, at which point CHINA actually be able to build a global quantum network for all of CHINA'S cryptographic needs.

There - fixed that for ya'. Human rights - so 20th century.

Cool they learn how to copy....

[nhat11]

quantum style!

Provably secure

[mbone]

There is a long, long history in cryptography of systems that were provably secure in principle proving not to be so in practice.

I'll believe any quantum crypto system is secure after attackers have been pounding on it for a decade or so.

Re:Provably secure

[ThatsMyNick]

This is not just another encryption scheme. What it is, is an encrypted stream, that cannot be intercepted without the knowledge of both sender and receiver. It is theoretically impossible for this to broken.

Re:Provably secure

[Anonymous Coward]

I guess the Achilles' heel or quantum cryptography will be transmission losses. If they have to retransmit qubits, they'll be leaking information.

Re:Provably secure

[jpapon]

It is theoretically impossible for this to broken.

According to current theory, yes. I agree that it is impossible, as far as we understand things. If faster then light communication was found to be possible, then it seems that this would no longer be secure.

Re:Provably secure

[Anonymous Coward]

A quantum mechanics 101 course might also help to give you a substantiated opinion on the topic at hand. Or, if you're lazy, just google "no cloning theorem".

Re:Provably secure

[Anonymous Coward]

It's theoretically impossible to brake the theoretical system. Practical implementations are fair game. On the most basic level you merely need a simple, cheap way to make A and B discard the session (i.e. believe it was compromised), that's enough to grind the system to a halt and go right back to more robust methods.

Hmmmmmm

[Pepebuho]

Why build a plane when you can TELEPORT the bomb?

That is easy for the chinese.

[140Mandak262Jamuna]

Going from point A to point B without going through any intervening points is quite easy for the chinese. They have gone from authoritarian regime to 1% - 99 % split oligarchy without going through the intervening democracy phase like America.

In Soviet China ...

[140Mandak262Jamuna]

In Soviet China space moves through the particles. [I know I know it is weak and does not make sense. But if I bring the meme back from the dead someone might make a better one.]

Can Someone Explain At 5th Grade Level?

[Anonymous Coward]

I've been completely unable to wrap my mind around quantum teleportation. I have a feeling it is due to the choice of labels that they are using. looking at the diagrams in the linked article, It seems remarkably like a beam of light rather than teleportation. But, they say that it is without passing through the intervening space. If that's the case, how is it targeted, received, measured? It seems dubious.

Can anyone explain what quantum teleporataion is at a 5th grade level? Perhaps using physical properties that the layman can relate to as metaphors?

Re:Can Someone Explain At 5th Grade Level?

[Eponymous Hero]

unfortunately this is beyond most 5th graders. any analogy for laymen will always fall short. analogies for those familiar with QM are tough enough as it is. but here's a classic bob and alice example: http://en.wikipedia.org/wiki/Quantum_teleportation#Motivation

Re:Can Someone Explain At 5th Grade Level?

[elsurexiste]

Under certain circumstances, two particles like electrons or photons (that's light) get related in such a way that, if you look at a certain characteristic on one particle, you'll know for sure not only the value for your particle, but also which value the other particle has. Thing is, most scientists, but not all, think these characteristics are random and don't have a "real" value until they are measured, so they say that, when you know the value on one particle, it "teleports" the result to the other particle, so it can know which value should have. There's another problem: this teleportation is faster than the speed of light, something that physicists don't like.

Let's say that you have bunnies that can be GOOD or EVIL, and behave like those particles. Let's say they are in a box and, before you see them, they can be either GOOD or EVIL. Once you open the box and check them, you can say "This bunny is a GOOD one!" or the EVIL bunny jumps at your face. Now, let's say that two twin bunnies are born and put in separated boxes, and you know that one is the GOOD one and the other is the EVIL one. They have become "entangled". You keep one and give another one to a friend. Now, when each is on their houses, you open your cage and check your bunny. Let's say is the GOOD one. Now, you know for sure that your poor friend has the EVIL one: it has "teleported" that knowledge.

If you are thinking the bunny knew all along whether it was GOOD and EVIL, well, a few scientists also think that way, but for that to work out (there's some heavy math behind it), information *must* be able to travel faster than light, so we can't solve the problem this way (who knows, maybe Einstein was wrong!).

Re:Can Someone Explain At 5th Grade Level?

[Anonymous Coward]

Thanks for the link. I get the Alice and Bob explanation. And I get the desirability of the entanglement theory and faster than light(FTL) transfer.

I do NOT get the "without passing through intervening space" angle at all. Even reading the article it sounds like they just transmitted some data via a laser link! Exactly the way we transfer bits via a laser link. Regardless of whether it is via free space optics or fiber, how is this "without passing through intervening space". The "without passing through intervening space" more than implies that the qubit state change just occurs by frickin magic(FM). I have difficulty comprehending frickin magic and FTL FM requires more faith than I can muster.

Re:Can Someone Explain At 5th Grade Level?

[Eponymous Hero]

ok how about this analogy. the qubit is a piece of information, not a physical entity that can physically move. this is why they say it does not move through space. compare a qubit to a meme. let's say you and i are like an entangled pair of photons. a meme resides inside my head: it's a state of my perception, equivalent to a qubit. i speak my idea out loud, and phonons carry the vibration across air-filled space to your ears (like the laser beaming the 2 classical bits of info) where it is decoded and reinterpreted by your brain to be the same meme. during that action it's important to consider the phonons as not the same thing as the idea. the idea never left my head even though i transmitted it. then let's say you agree with the meme, and now we're of like mind. in the experiment, the one photon essentially received information via classical means (the laser) from the other photon and decided to agree with it because it was entangled.

Scaling up

[jdavidb]

and perhaps most excitingly, the researchers seem confident that their system will scale up from 97km to distances capable of reaching orbital satellites

Actually, what would be most exciting would be if they could scale up from qubits to about 86.6 kilograms of organized mass...

Why is 97 km different than 16 km?

[mcmonkey]

Once you have the know-how and the hardware to do this, how is 97 km different from 16 km different from across the room?

Part of this is getting photons from point A to point B. But with fibre optics, couldn't they do 1000 or even 10,000 km with the same effort as 97?

Re:Why is 97 km different than 16 km?

[_0xd0ad]

The photons must remain in quantum entanglement while one photon is transmitted to the destination. A photon traveling through a glass fiber loses its quantum entanglement fairly rapidly.

China for all our "cryptographic needs"?

[Squidlips]

Sounds Great!

Security though overlooking the obvious -

[Darth Snowshoe]

I'm not sure I get why this method is thought to be any more secure than a conventional line-of-sight laser link.

It seems as though a line of sight laser that had conventionally encoded data in it would be pretty secure. Well, you'd have to get close to the laser light to observe it, and maybe use some super-fancy optics to couple to it and make a copy of the data. Highly unlikely but possible. But if the (assumed full-duplex) beams were obstructed, the link would be assumed compromised and sending could be halted.

In the case of the quantum version, it is said that the photons are entangled, so if an adversary inspected them, he'd "collapse the wave function" and it would be obvious to both the receiver and the sender, is that right? But, because its an optical beam, some amount of those entangled photons diverge, go astray, and are not ever received (at the receiver.) How does the sender distinguish between those that are legitimately received and those that go astray? Between those that are intercepted by an adversary and those that go astray? Could not then an adversary just choose to inspect those photons that weren't going to make it to the receiver anyway? And then, by 'collapsing the wavefunction' him or herself, be privy to (some portion of) the message?

Re:Security though overlooking the obvious -

[_0xd0ad]

Conventional lasers use a beam consisting of millions of photons, and some percentage of them have to reach the destination. In the quantum version, individual photons are transmitted, and all must reach the destination, or both transmitter and receiver will know that the secure link has been broken. Additionally, it's theoretically impossible to eavesdrop without either breaking the quantum entanglement, or blocking the photon (or both). Either way, both parties will detect it.

Re:Security though overlooking the obvious -

[Darth Snowshoe]

Ah, but the abstract of the paper itself says "Over a 35-53 dB high-loss quantum channel, an average fidelity of 80.4(9) % is achieved for six distinct initial states." That sounds like a lossy channel to me. Plus, I simply don't believe it's possible to send a laser beam over X kilometers, including an atmosphere, and have them ALL reach their destination - it's a limitation of the medium.

Also, the Physics ArXiv blog post for this paper includes this;
"Inevitably photons get lost and entanglement is destroyed in such a process. Imperfections in the optics and air turbulence account for some of these losses but the biggest problem is beam widening (they did the experiment at an altitude of about 4000 metres). Since the beam spreads out as it travels, many of the photons simply miss the target altogether. "

and

"That's interesting because it's the same channel attenuation that you'd have to cope with when beaming photons to a satellite with, say, 20 centimetre optics orbiting at about 500 kilometres. "The successful quantum teleportation over such channel losses in combination with our high-frequency and high-accuracy [aiming] technique show the feasibility of satellite-based ultra-long-distance quantum teleportation," say Juan and co."

So it looks to me as though even the paper's author is admitting some "channel losses". The question I still have is, how is it possible to distinguish channel losses from adversarial interception of photons?

Re:Security though overlooking the obvious -

[_0xd0ad]

Well, I went ahead and downloaded the PDF (surprisingly not paywalled).

It describes it as (paraphrasing slightly):

Alice has a photon of unknown quantum state and wishes to transfer it to Bob, who is at a distant location. Charlie first distributes an entangled photon pair to Alice and Bob, respectively. Alice now has two photons, and performs a joint Bell-state measurement (BSM) on them. The state of Bob's entangled photon is instantaneously altered by Alice's measurement. Alice then transmits the BSM result (meaningless on its own) to Bob via a classical channel. Based on this result, Bob can apply the appropriate unitary transformation which will convert the state of his entangled photon into the original state of the unknown photon.

So it sounds like the information is not teleported until Bob and Alice have successfully received a pair of entangled photons. Losses simply interfere with Bob's ability to receive entangled photons (Charlie and Alice are in the same physical location).

Re:Security though overlooking the obvious -

[Darth Snowshoe]

Geez I'm sincerely sorry, I don't mean to pepper you with questions, I should just go ahead and hire on optical physicist to explain this to me, but here goes -

Is there a way for Alice to discern that a specific entangled photon, sent from Alice (or Charlie) was received by Bob? Alice gets an entangled photon, assumes that Bob has the entangled twin for it, and does her joint Bell-state measurement. Now, Bob's entangle photon is instantaneously altered, right? But Alice doesn't really know whether that photon is in Bob's possession, or Max's (the adversary), does she? She knows that she sent some amount of entangled photons in Bob's direction, and that maybe Bob received X% of them. Max can intentionally scoop up (100-X) percent of the photons, and, Alice not being able to discern which actually reached Bob or not, she will encode her message using all of her entangled photons. Presumably she and Bob will implement some kind of error correction scheme to make up for losses.

I guess what I'm saying is that there's leakage inherent in any system that's sending photons through free-space, and neither Bob nor Alice has a realistic way of discerning natural losses from intentional third-party interceptions. I can't imagine Bob sending back through a classical channel "Hey Alice I got photon #12 go ahead and do your BSM now!", but again that could be spoofed because it would be on a classical channel. Max is probably sending back variants of that same message with the numbers of all the photons he received.

The third party then would have to intercept the classical channel (but that should be easier, because it's classical) and somehow match bits of information from that to the bits he'd intercepted or eavesdropped on. There's nothing in even the ideal system that prevents this. The only way to really prevent this is to make sure every entangled photon is accounted for.

But the other aspect of this is that it sounds like a supremely fragile system. It's a great step forward for security (maybe) but not reliable or robust in the kinds of ways that you might wish for in a system meant to convey strategic communications.

Re:Security though overlooking the obvious -

[Zaphod The 42nd]

So it sounds like the information is not teleported until Bob and Alice have successfully received a pair of entangled photons. Losses simply interfere with Bob's ability to receive entangled photons (Charlie and Alice are in the same physical location).

^^^ This.

Re:Security though overlooking the obvious -

[Zaphod The 42nd]

This has been done before. TFA notes that there was a previous record of doing the EXACT SAME THING but over a shorter distance of 16 km.
The only story here is managing to do it over a long distance.

Doesn't that inherently imply that there ARE problems? There's difficulty in doing it over larger and larger distances, related to the beams. It just seems obvious, like, DUH they're having problems doing it over longer and longer distances. That is the WHOLE POINT. That's what they're getting better at.

And you're missing the point of Quantum Teleportation. It IS NOT teleportation. They're fundamentally different things. Don't confuse yourself just because of a word. Context means everything. The channel isn't lossy because transferring the qubits isn't the quantum teleportation! That is just a set-up for the quantum teleportation. Once both parties A and B have entangled photons, THEN the quantum teleportation begins.

Classical information can never be transmitted using entanglement. So don't think this was EVER about communicating information; its not and you can't. So saying its a "lossy channel" doesn't even make sense. You don't use this to transfer information. The only current practical purpose of transmitting quantum data, which is otherwise just uncontrollable garbage, is for the purposes of encryption, where using a qubit as the nonce ensures that no man-in-the-middle attacks can be made, as any other party attempting to access the quibits would necessarily ruin the entanglement, and make it obvious that it was insecure.

Re:Security though overlooking the obvious -

[_0xd0ad]

It's not really known whether or not Bob's photon actually changes, or whether it's simply been in the same state as Alice's photon all along. If it changes that would imply that the information moved faster than the speed of light, which poses problems under current models. If it's been that way all along, the only thing that changes is that Alice now knows what state it's in.

In either case, Alice can tell Bob which quantum operation to perform on the entangled photon to determine the state of Alice's original photon. Intercepting this would tell you nothing unless you have one of the entangled photons, since the state of Alice's entangled photon is assumed to be random when she measures it. Bob's entangled photon has the same quantum state as Alice's does, and when he performs the correct operation, he finds the state of the original qubit.

I assume there must be some way to determine whether both Alice and Bob have an entangled pair of photons before Alice transmits which transformation Bob should use. Otherwise, it seems like someone could intercept an entangled photon intended for Bob and also intercept the transmission where Alice reveals which transformation will yield the encoded qubit.

Re:Security though overlooking the obvious -

[_0xd0ad]

Not the exact same thing - quoting from the paper,

Most recently, following a modified scheme, quantum teleportation over 16 km free-space links was demonstrated with a single pair of entangled photons. However, in this experiment, the unknown quantum state must be prepared on one of the resource entangled qubits and therefore cannot be presented independently. In our experiment, we demonstrate quantum teleportation of an independent unknown state...

Re:Security though overlooking the obvious -

[Zaphod The 42nd]

That's true, but I don't think it changes enough to make a difference for this point. They're sending entangled photons and then sending quantum information about how to read them after, rather than preparing them ahead of time. But both ways they're having to transfer entangled photons over a distance, and I think they're doing it the same way in both.

Re:Security though overlooking the obvious -

[Zaphod The 42nd]

Sorry, sending *classical information about how to read them afterwards, not quantum.

Re:Security though overlooking the obvious -

[Anonymous Coward]

"So it looks to me as though even the paper's author is admitting some "channel losses". The question I still have is, how is it possible to distinguish channel losses from adversarial interception of photons?"

Generally speaking, you can't. But you can pessimistically assume that all the noise in the channel is due to an eavesdropper and, if the noise still isn't too high, use that to derive an upper bound on how much information the eavesdropper has about the eventual shared key. You can then use classical hashing (in a process called "privacy amplification") to reduce both the size of the key and the proportional amount of information an eavesdropper can have to however low a level you desire.

Re:Security though overlooking the obvious -

[_0xd0ad]

Thank you for your insightful explanation of why this would never work - if you were designing it.

We've known the Pledge and Turn for awhile...

[rsmith84]

So that makes this The Prestige... Anyone else get the vision of the amazing Tesla machine that Hugh Jackman commissioned to achieve "The Real Transported Man"?

Re:We've known the Pledge and Turn for awhile...

[Beardo the Bearded]

No, we didn't.

Re:We've known the Pledge and Turn for awhile...

[Beardo the Bearded]

Hey, Friday is my day to post.

Re:We've known the Pledge and Turn for awhile...

[Beardo the Bearded]

No, you get Thursdays. My day is Friday.

Re:We've known the Pledge and Turn for awhile...

[Beardo the Bearded]

Will the two of you SHUT UP?

Re:We've known the Pledge and Turn for awhile...

[Anonymous Coward]

Wow, what a boring routine.

Re:We've known the Pledge and Turn for awhile...

[Beardo the Bearded]

The best part is that is took us three minutes to post all of those messages;

Re:We've known the Pledge and Turn for awhile...

[bejiitas_wrath]

But that machine kept you at the source and transmitted your copy. Therefore you would have to kill yourself over and over. It would be useful for replicating a bag of 100 dollar bills expotentially though. You would be rich. You could buy 10 gold bars and replicate them with the machine to create 10,000 gold bars, sell them then make another 10,000. Think about it...

Think Like a Dinosaur

[Anonymous Coward]

Like every other Chinese mechanism, it actually only copies the subject matter on the other end.

But most importantly...

[Anonymous Coward]

Is Gordon Freeman involved?

Re:WE don't need this science trash

[Anonymous Coward]

Obvious troll is obvious.
 
But I would like to point out that this technology (or, the tech it will lead to) could be key to the claim of #1 superpower in the near future. We really ought to put some effort back into being intelligent.

Who is this 'we' you refer to?

[PPH]

at which point we'll actually be able to build a global quantum network for all of our cryptographic needs.

Are you a member of the Chinese Army?

Re:WE don't need this science trash

[Anonymous Coward]

Obvious troll is obvious

Water is wet.

We really ought to put some effort back into being intelligent.

Some of us are intelligent. The rest believe in God.

Don't add significant figures

[nedlohs]

It shows a complete lack of understanding of science.

And of course the actual distance will have been 100km which someone who does understand significant figures converted to 60 miles for Americans. Followed by a moron deciding to convert it to 97 km because they are scientifically illiterate.

Re:Don't add significant figures

[DerCed]

No, not at all. It was 97 km. The article is titled "Teleporting independent qubits through a 97 km free-space channel".

Re:Don't add significant figures

[Anonymous Coward]

Or you didn't bother to RTFA. It's 97 km in the journal article, 100 km in the press release, and 97 km in the /. blurb, which is, in fact, 60 miles to the correct precision.

Secondly, do you have any idea how many significant figures are in that "100" km value? Is there only one significant figure? Are there two? How would you know if you only bothered to read the /. blurb and the first sentence of the press release?

It's time for you to get off your high horse and do a little bit of becoming literate yourself.

Re:Don't add significant figures

[nedlohs]

I'm happy to have misinterpreted it. I'm not happy that a journal isn't using SI units but that's entirely unrelated .

our quantum network needs

[Anonymous Coward]

don't expect china to hand over an instantaneous communication method which can't be eavesdropped on. Countries like america would use it with their stealth bombers they want to control china with.

Transporting information

[Anonymous Coward]

> This means that quantum data has been transmitted from one point to another, without passing through the intervening space.

I think this is the interesting part, since up to now it had been assumed that quantum entanglement could not transfer information.

Great..

[Anonymous Coward]

Before you know it, those darned Chinese physicists will be popping up everywhere.

Metric or Imperial Trillions?

[Anonymous Coward]

If we have a 72-kg (158 lb.) person made mostly out of water, that's about 4,000 moles

What you say doesn't make any sense, as one European mole has a mass of about 100 grams. If one human consisted of 4000 moles, said human would have a mass of about 400kg! Turning it the other way around, one out of 4000 moles making a 72-kg-human would have a mass of just 18g. That must be some significantly smaller species than the European mole!

Dude! Did you use our fine, European, metric mole or did you calculate everything in imperial moles?!

Aww

Re:Metric or Imperial Trillions?

[Khyber]

He used the SI mole, which neither Americans or Europeans apparently understand.

Re:Metric or Imperial Trillions?

[Anonymous Coward]

The French Système International d'unités sounds very European (or Canadian?!) to me, so he might have used the small French water mole ... and water is coincidentally about 18 grams per mole!

Re:Metric or Imperial Trillions?

[Anonymous Coward]

WHOOOOOSH!

Numbers in a hat

[V-similitude]

I still don't really understand entanglement. Any time I hear it explained it sounds like it's really nothing like instantaneous anything. It seems like it's no different than putting two numbers in a hat, pulling one out at random, and then sending the hat to someone and say . . . when I look at mine and send you that info, we both know what yours is!

Re:Numbers in a hat

[shadowofwind]

Except that 'when I look at mine', I don't have to 'send you that info', it happens instantaneously. Sending the hat is the only thing that takes time. That's a pretty big difference.

Re:Numbers in a hat

[FrangoAssado]

[ouch -- overly long comment ahead... I wonder if anyone will read it :( ]

I have also never seen a good popular explanation of entanglement: either they go full weirdo saying things like "instantaneous something" or don't really explain entanglement, like your example about numbers in a hat. The problem is, to understand exactly what physicists understand by "quantum entanglement", you first must understand measurement, and in particular, that you can choose many different ways to measure each particle from the entangled pair. If you're willing to spend some time, I recommend the excellent series of lectures starting in this video. The material is pretty self-contained, except some matrix algebra and complex numbers. The lectures are given by Leonard Susskind, a famous physicist.

Now, if you just want to understand why entanglement is different then your "numbers in a hat" example, I'll try to explain as simply as I can with a simple example (which has the basic idea of Bell's inequalities and their violation, you can search wikipedia if you like).

OK, consider a "game" with these elements:

• (1) two people, Alice and Bob, the players in the game
• (2) both Alice and Bob each have a coin. Their coins are fair (i.e., 50/50) and, when flipped, give the result "0" or "1". Call the results of Alice and Bob flipping their coins ca (for "Coin-Alice") and cb (for "Coin-Bob"). Clearly, ca and cb are completely unrelated, because the coins are fair. Alice can see the result of her coin, but NOT Bob's, and vice-versa.
• (3) the hat from your example, which generates either two "0"s or two "1"s. You'll always give one of the numbers to Alice and the other one to Bob, and each of them can NOT see what the other one got. Call the two generated numbers ha and hb (for Hat-Alice and Hat-Bob). So, you'll always have either ha=hb=0 or ha=hb=1.
• (4) both Alice and Bob each have a piece of paper where they have to write either "0" or "1". Call the two written numbers pa and pb (for Paper-Alice and Paper-Bob). Each of them can't see the other one's paper.

The game is played by Alice and Bob collaborating to win -- either they both win or they both lose. To play, they can discuss their strategy, after learning the rules which I'm about to explain. But once the game starts, they can't talk anymore (i.e., no information can pass between them).

The rules of the game are as follows: when the game starts, Alice and Bob are given the numbers from the hat (ha and hb), then flip their coins (ca and cb) and write in their papers (pa and pb). They win if the resulting numbers satisfy the following equation:

pa XOR pb = ca * cb

and lose otherwise. Here, XOR is the usual XOR operation on bits, and "*" is the usual multiplication. Remember that all numbers in the equation (pa, pb, ca, cb) are either "0" or "1"). Also note that the numbers from the hat are not used to determine if they win or lose, but they can use the hat numbers to write their answers, according to whatever strategy they decided.

Now, note that if they both always write "0" in their papers, ignoring the hat completely, they win 75% of the time, because 0 XOR 0 = 0, and ca*cb will only be different than 0 if both coins are 1, which happens only 25% of the time. It's not too hard to prove (mathematically) that if their coins are indeed completely fair, any strategy they use will give them at most 75% of chance to win, it's impossible to do better without cheating.

So far, nothing involves anything quantum, and there's no entanglement. What I described is called a "Bell inequality" (win probability <= 75%), you can look up Wikipedia for a mu

Re:Numbers in a hat

[marcosdumay]

It seems like it's no different than putting two numbers in a hat, pulling one out at random, and then sending the hat to someone and say . . . when I look at mine and send you that info, we both know what yours is!

That's the best analogy with classical concepts you may get. It's quite like that, except that the papers don't decide what number is on them untill somebody looks. But if you get one, yeah, the other person is getting the other number.

Re:Numbers in a hat

[V-similitude]

Interesting, thanks for the explanation. But personally, I find it all too... contrived. I just have a feeling something else is really going on. Especially given that the realm it applies to is so restrictively tiny that the slightest perturbation of the experiment can change everything, it seems equally likely that we're just missing something. Until there's some real, practical, use for these results, I'll remain highly skeptical.

Re:Numbers in a hat

[FrangoAssado]

I just have a feeling something else is really going on.

A lot of people seem to feel that way. If was even common among physicists in the beginnings of Quantum Mechanics (Einstein -- among many others -- was never satisfied with the theory, and tried without success to find something better).

I'm not sure myself, but it seems that when you begin to understand the math, you realize that it's actually very simple at the bottom -- the same very basic rules predict and explain so many wildly different things we can measure -- interference (the wave-particle duality stuff), the uncertainty principle, entanglement, quantum tunneling, etc. -- that it seems unlikely that there's some simpler explanation that will fit everything as well as Quantum Mechanics.

But one can never be sure :)

Re:WE don't need this science trash

[spazdor]

Tautological tautology is tautological!

Re:WE don't need this science trash

[Anonymous Coward]

We left it up to "God" for thousands of years. What did we get? Religious wars, the dark ages, the crusades...Let me ask, what has God done for you ever? Science keeps giving as long as we do it. Science isn't a thing, its the name of a method for defining workable facts.

Oh and LOL at how you think the US is the only country that believe in God. That's flat out wrong, we have every religion here and some of them believe in dozens of gods, some of them believe in aliens...Fuckin A right, didn't you know Jedi is a recognized religion in the US? That term didn't even exist 50 years ago.

photon ring

[Anonymous Coward]

Is the a photon equivalent to a superconducting magnet?
As in creating two synchronized rings on entangled photos that will persist for 3 years, giving you a buffer of photons and a buffer size for communications.

FYI

[spazdor]

Electricity does not travel at the speed of light.

Pirated qubits

[high_rolla]

How do we know they didn't just pirate the qubit?

Weaponization?

[Slicker]

So... Is doing a bunch of these in parallel on the horizon? I mean, perhaps they could use it to produce an explosive material at a distant location without having to traverse there.. Or perhaps just something else that would be damaging...

Other free space quantum channels

[Anonymous Coward]

2003 http://www.quantum.at/research/quantum-teleportation-communication-entanglement/long-distance-free-space.html
2005 http://www.quantum.at/research/quantum-teleportation-communication-entanglement/free-space-quantum-channel.html
2007 http://www.quantum.at/research/quantum-teleportation-communication-entanglement/entangled-photons-over-144-km.html
Since then they've been making gear which goes on ISS
http://www.quantum.at/quest

wrong

[Anonymous Coward]

teletransmission != teleportation

Re:"Think like a dinosaur"... apk

[Anonymous Coward]

go put a sock in it, alex.

qunonsense

[Anonymous Coward]

"without passing [the qubits] through the intervening space"

Buuuuulllllll Shiiiiiiiiiiit!

Technically true, but only in the same way that transmitting information about the state of a transistor on a chip does not transmit the chip across the intervening space.

So when do we get our ansibles?

[jbgeek]

They'd really help with comms to/from future robotic spacecraft, mars bases, etc. :-)

We?

[bobvious]

"... at which point *we'll* actually be able to build a global quantum network for all of our cryptographic needs."

What do you mean "we" wide-eyes?

Minor Correction

[arceum]

The above says "performed by another Chinese team back in 2010" but it 16km feat was first demonstrated by the same team

Hit & run moddowns off topic troll?

[Anonymous Coward]

Is that the best you've got, troll -> http://science.slashdot.org/comments.pl?sid=2844535&cid=39977699 ?

Apparently so, and I must ask you a question:

IS YOUR FAVORITE COLOR "TRANSPARENT" OR WHAT??

(I state that because your tactics and methods are easily seen through... too easily.)

APK

P.S.=> Trolls with off-topic trolling replies right after a down moderation of a post that had nothing but facts in it per the link above I posted where the ac troll coward obviously downmodded my post, logged out, & trolled by ac stalker/harasser replies is TOO obvious as to his "modus operandi" after all... pitiful! apk

"Hit & run moddowns" off-topic troll?

[Anonymous Coward]

Is that the best you've got, troll -> http://science.slashdot.org/comments.pl?sid=2844535&cid=39977699 ?

Apparently so, and I must ask you a question:

IS YOUR FAVORITE COLOR "TRANSPARENT" OR WHAT??

(I state that because your tactics and methods are easily seen through... too easily!)

APK

P.S.=> Trolls with off-topic trolling replies right after a down moderation of a post that had nothing but facts in it per the link above I posted are easily dispatched, especially when all I posted was facts... then, where the ac troll coward obviously downmodded my post, logged out, & trolled by ac stalker/harasser replies is TOO obvious as to his "modus operandi" after all as to HOW & WHAT he does/operates on /. here is also TOO obvious and... pitiful! apk