Photograph courtesy Jonas Mlynek, ETH Zurich
Published August 14, 2013
It might seem like something straight from the Star Trek universe, but two new research experiments—one involving a photon and the other involving a super-conducting circuit—have successfully demonstrated the teleportation of quantum bits.
If that sounds like gobbledygook, don't worry. We got in touch with one of the researchers, physicist Andreas Wallraff, of the Quantum Device Lab at the Swiss Federal Institute of Technology Zurich, to explain how his team and a team based at the University of Tokyo were able to reliably teleport quantum states from one place to another.
People have done this before but it hasn't necessarily been reliable. The new complementary research, which comes out in Nature today, is reliable—and therefore may have widespread applications in computing and cryptography.
Before we talk about the nitty-gritty part of teleportation, we need to define a few key words. Let's start with a regular, classical bit of information, which has two possible states: 1 or 0. This binary system is used by basically all computing and computing-based devices. Information can be stored as a 1 or a 0, but not as both simultaneously. (Related: "The Physics Behind Schrodinger's Cat.")
But a quantum bit of information—called a qubit—can have two values at the same time.
"With the qubit, you can store more information because you have information in all of its possible states," Wallraff says. "Whereas in the classical memory system, only one can be stored." (More physics: "The Physics Behind Waterslides.")
Quantum teleportation relies on something called an entangled state. An entangled state, in the words of Wallraff, is a "state of two quantum bits that share correlations." In other words, it's a state that can't be separated.
If you have a classical 1 and a 0, for example, you can separate them into a 1 and a 0. But if you have qubits, the bits can be assigned both a 1 and a 0 at the same time—meaning they can't be separated into their individual components and must be described relative to each other. (If you'd like to know more about this, I recommend delving into "Quantum Entanglement" on the Caltech website.)
Photograph courtesy Arkady Fedorov and Lars Steffen, ETH Zurich
Diving Into Teleportation
Now that we have a small working vocabulary, we can delve into what Wallraff and team actually did.
Let's go back to Star Trek.
"People automatically think about Star Trek when they hear teleportation," says Wallraff. "In Star Trek, it's the idea of moving people from point A to B without having the person travel that distance. They disappear and then reappear."
What happens in quantum teleportation is a little bit different. The bits themselves don't disappear, but the information about them does.
"That's where the relation to Star Trek comes in," says Wallraff. "You can make the information disappear and then reappear at another point in space."
So how does this work? Remember, we're talking about quantum bits—which can hold two possible states at the same time.
"You can ask yourself, 'How can I transport the information about this bit from one place to another?'" says Wallace. "If you want to send the information about the qubit from point A to B, the information at point A [contains] 0 and 1 simultaneously."
Illustration courtesy Akira Furusawa
It's impossible using classical bits to transmit this information because, as we learned earlier, the information can be stored as 1s or 0s but not both. Quantum teleportation gets around this problem. (Related: "Physicists Increasingly Confident They've Found the Higgs Boson.")
This is where those entangled states I mentioned earlier come into play. In quantum teleportation, a pair of quanta in an entangled state is sent to both a sender—which I'll call A—and a receiver—which I'll call B. A and B then share the entangled pair.
"The sender takes one of the bits of the entangled pair, and the receiver takes the other," says Wallraff. "The sender can run a quantum computing program measuring his part of the entangled pair as well as what he wants to transport, which is a qubit in an unknown state."
Let's untangle what he said: The sender—A—makes a measurement between his part of the entangled pair and what he wants to transport.
Back to you, Wallraff.
"So we have this measurement, and that's what is sent to the receiver via a classical bit," he says.
The receiver—B—receives the measurement between A's part of the entangled pair and the unknown qubit that A wants to send. After B receives this measurement, he runs a quantum computing algorithm to manipulate his part of the entangled pair in the same way. In the process, B re-creates the unknown qubit that A sent over—without receiving the qubit itself.
I realize this is confusing.
Photograph courtesy Akira Furusawa
But Why Is It Useful?
The advances these two research groups have made may improve the way quantum bits are sent, leading to faster processors and larger-scale encryption technologies.
Encryption technology—which is used by everyone from credit card companies to the NSA—is based on the fact that it's really, really hard to find factors of very large prime numbers. And quantum computing is extremely useful for factoring very large prime numbers.
Dividing or multiplying numbers is fairly easy for any computer, but determining the factors of a really large 500- or 600-digit number is next to impossible for classical computers. But quantum computers can process these numbers easily and simultaneously.
Credit card companies, for instance, assign users a public key to encode credit card information. The key is the product of two large prime numbers, which only the website seller knows. Without a quantum computer, it would be impossible to figure out the two prime numbers that are multiplied together to make the key-which protects your information from being shared. (For more info, read this really useful guide about the basics of quantum computing from the University of Waterloo.)
"If you wanted to use classical bits to do this, it wouldn't be efficient," says Wallraff. In other words, classical computers—the ones we use now for most stuff—can't do any of the things quantum computers can do on a large scale.
So while we might not be beaming Scotty up just yet, our computers, it appears, are one step closer to doing so.
> "The advances these two research groups have made may [lead to] larger-scale encryption technologies. Encryption technology is based on the fact that it's really, really hard to find factors of very large [semi]prime numbers. And quantum computing is extremely useful for factoring very large [semi]prime numbers."
Apart from the confusion between prime and semiprime numbers, you have one very important thing backwards here.
It's *easy* for modern computers to encrypt something. That is not the issue. What finding the prime factors does, however, is to allow you to *decrypt* it. The issue is that if it becomes easy to *decrypt* something by quickly calculating the prime factors of your key, then all modern encryption fails.
So this advance isn't going to make encryption somehow easier or more "large-scale" than it already is, as you are implying. Rather, the fact that "quantum computing is extremely useful for factoring very large [semi]prime numbers" means that if this succeeds, it will completely destroy encryption as we know it today.
This is a very important issue, and shouldn't be confused.
this talks of qubits is a very beginning of the teleportation theory, the exchange of the "information" runs faster then C speed, it works immediatly, doesn't make a difference if 1ft distance or from one galaxy to another one, becose of a special relationship between particles, if one particle changes its spin, the bonde particle does the same in the very same moment.
This is not teleportation in the classic sense but certainly a prelude. Teleporting information is the beginning and will be an essential part in the actual teleporting process in the future.
When you say 'recreate' , does that mean more than one !?!? Remember the movie 'The Fly' ...and how Gena Davis said the food tastes 'synthetic'...is this due to not entirely having all the particles or a deeper need to understand the smallest of matter !?!??!
I wonder how many prime numbers they have been able to factor? Example, please! If the rest of the artiicle is as accurately written as the line about "factoring large prime numbers" we need not worry!
Technical question: Does the data transport between locations occur in actual ZERO time, or does it travel at some greater-than-C speed?
Other question: Do these scientists wear cone-shaped hats with stars and moons on them?
I have a bit that is both 1 and 0 in one hand, and another that is both 1 and 0 in the other hand: Teleportation! Oh, and then there's the fact that - contrary to what was said in the article - it's very easy to factor large prime numbers: the factors are 1 and the number itself.
I just finished my CS degree, and I have to say that you shouldn't take these "pronouncements" by the media too seriously. Much of "science" is nothing more than guessing, although they never tell you that. Instead, it is hyped as "the latest" "truth", which in five years will be replaced with "the latest truth", and in five years will be replaced with... Exactly.
The article says - "Encryption technology—which is used by everyone from credit card companies to the NSA—is based on the fact that it's really, really hard to find factors of very large prime numbers"
Its very easy to find the fact the factors of very large prime numbers. Its very difficult to find the factors of very large SEMIPRIME numbers...
But you got it right when you explained it later on...
"People automatically think about Star Trek when they hear teleportation," says Wallraff.
No, I was thinking of Star Trek and The Fly simultaneously.
Teleportation, if we understand it like shifting in the space of material object with velocity equal to the velocity of light in empty space, such event it isn’t possible…why? See Q&A www.kanevuniverse.com
I for one love to have articles written at me that assume I don't even have a high-school physics background or a curiosity above that of Sarah Palin. It's so nice to be treated like an idiot by the author of an article. FINALLY SOMEONE GETS ME
so does this mean that you can send a 1,0,10,01 this way or just a 10,01 or only the difference between A and point B in that you dont know if its a 10 or a 01 you just know that there either there the same or not the same ...
This is a good try at understanding a complex subject but there are a lot of misunderstandings.
It's certainly not impossible to factor large primes and breaking the relatively simple encryption that is used by most organisations to provide a semi level of security on the internet is well understood . There is a wealth of mathematic and applied knowledge on the subject if you know where to look. What is likely to be difficult for most people is figuring out where to look. People who are interested in this stuff understand that we are all basically naked on the internet as far as the NSA or other large and well funded organisations are concerned.
It's most likely that the encryption standards we use today for banking and industry were already cracked before they were released into the public space.
Encryption is an arms race. Back in WWII substitution cyphers like Enigma were very difficult to crack. The invention of computers made them trivial to crack, but also allowed more sophisticated encryption that was very difficult for such computers to crack. Quantum computers make these encryption systems trivial to crack, so we have to create quantum encryption systems. Of course, quantum computers will allow the calculation of other stuff that we can't calculate now, just as modern computer technology is useful for other things besides cracking substitution cyphers.
Ok, so basically one could sum this all up by saying Part A wants to transmit 5 and it knows the measurement between itself (A) and the receiver (B) is 4.
Thus we just transmitted the number 9. Wow.
Are you telling me the this is quantum mathematics?
Blarney. What you are describing already takes place with metadata surrounding every symbol. SO, all you are describing is compounding the firmware at each end to make it easier to send "mixed messages". You are trying to describe the reverse of the "Bision or hearing process which already takes place in the human body...only not doing a good enough job of it.
It is fascinating that a computer could be based upon the imaginary particle that is the photon. It is as though the tax payer is being robbed by fools.
"Encryption technology—which is used by everyone from credit card companies to the NSA—is based on the fact that it's really, really hard to find factors of very large prime numbers. And quantum computing is extremely useful for factoring very large prime numbers."
Some widely used and important encryption technologies such as public-key cryptography depend on the fact that it is really, really hard to find factors of *nearly* prime numbers. Quantum computing is expected to be extremely useful for factoring very large nearly prime numbers.
Many encryption technologies do not depend on nearly-prime numbers. In fact SSL/TLS, which is widely used (for example in HTTPS) uses public-key cryptography for several functions at connection set-up, but then uses a shared key (sent over the public-key encrypted link, and regularly rotated) to encrypt the actual information being transmitted.
"Credit card companies, for instance, assign users a public key to encode credit card information. The key is the product of two large prime numbers, which only the website seller knows. Without a quantum computer, it would be impossible to figure out the two prime numbers that are multiplied together to make the key-which protects your information from being shared. "
This is so wrong it's hard to even start. Credit card companies do not assign users public keys- at least not in the context of protecting "your information from being shared".
Even websites using SSL to protect credit card transactions do not assign users a public key. No website assigns people public keys, unless they are using client-side SSL certificates to authenticate users. Very few sites do this- I've run some that do, and it is a really good way to improve security in some cases, fwiw.
It is not impossible to figure out the two prime numbers that are multiplied together to make the key. It is extremely difficult to do if the constituent primes are large enough and are chosen randomly enough. Keys based on 40bit factors have been broken (factored) by brute force. Recently, it's been demonstrated that many larger keys have been created with poor pseudo-random number generators and are susceptible to being broken (factored).
I don't know if the descriptions of Quantum Entanglement are similarly in error or not.
The name "quantum teleportation" was coined by Bennett et al in 1993. This most unfortunate name leads to all kinds of misconceptions such as, "while we might not be beaming Scotty up just yet, our computers, it appears, are one step closer to doing so." Quantum teleportation has nothing whatsoever to do with transporting people or things across space. Ask a physicist when they will use QT to move a single hemoglobin molecule across the lab. That means moving all the elementary particles and chemical bonds of all the atoms, while preserving their relative positions in space. That has nothing whatever to do with "quantum teleportation". Another common misperception is that QT can be used to send messages at faster than light speed. No, it can't.
What would be interesting is if you could send the classic bit with the qubit to a destination and decode it without a receiver. It could probably be with some kind of time/distance ending effect at the end of the process.
As if quantum physics isn't weird enough and isn't harder to grasp already ! In the case of this new research, I wonder the same things Jason does - at what distance and at what level of reliability did the experiments achieve. And also how does that compare to theoretical limits?
Also unclear about whether the speed from Point A to Point B is instantaneous, regardless of distance.
Best book I have read on this subject for a non-physicist is: Entanglement - The Greatest Mystery in Physics by Aczel. You can see from my questions that I still don't completely "get it."
I don't understand how's that different from simply shifting from binary systems and implementing cryptography to it?
I am wondering just how much distance can be traversed reliably through this sort of quantum teleportation. If we put a probe or a colony on Mars, and brought bits to Mars which were entangled with bits here on Earth, then could it be possible to communicate instantaneously? What about between galaxies?
Even a quantum computer would have a hard time factoring a prime number. Perhaps you meant finding prime factors of a large non-prime number.
Scotty is the one who does the beaming up, not usually getting beamed :)
I don't see how this is teleportation since the original still exists in the same place. It's just using math to make a copy. Instead of directly sending the information you get a variable and then have to plug it into an equation on the other end... therefore you haven't moved the thing itself.
@Stephen Blackstone Yuh, prime number factors are it & 1 !
As I've understood basic Quantum mechanics.. the rules are a bit different.. there isnt matter more like differing energy states .. In theory you could build a quantum teleporter.. but the computational power needed is dizzing each quantum bit that makes up u would have to be accounted for.... than received in same manner.. we have neither the tech or the engineering.. maybe one day.. but not soon and at the end would prob be cheaper to take conventional ways.
Quantum entanglement moves at over 10000 times the speed of light ( "Spooky action" )
@Menos Paam You're pretty sensitive. Grow up.
@Patrick ShirkeyYou sound an awful like some tinfoil alarmist. Make ridiculous claims and shift the burden of proof.
It's not the first time I come across one these claims that encryption standards are well known to be crackable by apparently the whole enthusiast community. Correct me though if I am wrong there hasn't been a single mathematical/CS institution to publicly come out and state that either AES or RSA have any flaws in their design. In fact they have held competition for prime number factorization and results have been lacking. I don't think you quite understand the claim that you are not aware that you are making. That these well known encryption standards have known weaknesses. That the CS communities within NSA or other large institution have somehow managed to keep under wraps. That they posses so much knowledge that they are light years ahead of the rest of the community. These is really not very likely scenario.
Encryption standards have been tested in criminal cases only to come out the victor for anything other than brute force/dictionary attack on passwords.
The vast majority of these security bypass that you hear of occurring in the internet are exclusively related to humans not following secure protocols, and never since DES, has it been the faults of the protocols themselves.
@M H the very large prime number itself, and 1.
Great point, particullarly about the "no-cloning teleportation and no-teleportation theorems". Those (2) theorems, point out that basic "Sar Trek" teleportation is impossible because, particularly the no-teleportation theorem states "arbitrary quantum state cannot be measured with complete accuracy" and since that is the case how can you transmit an object with a aribitrary quantum state (Based on my understanding, anything other than a single item like a photo) is not able to be transmitted with complete accuracy.
There is something called "imperfect cloning" which is the transmission of the obvious, an imperfect clone of the object you want to transmit.
@Jason McNeill An ansible would be a big leap into space. not that teleportation isn't. I am quite impressed with results moving from theory to reality starting with the theory of quantum computing.
@edward delean Well, actually, of course,it's quite easy to factor a prime number if you know it's prime already. What is meant, as I understand it, is that it's exceedingly hard to factor a number that you know is the product of two extremely large prime factors.----- Merely elaborating on your correct assessment of what was intended.
@Mike Tupper I'm not a physicist, but I play one on TV....
First step, in classical terms: stop thinking of this as 1's and 0's. It's actually On and Off.... meaning electrons are travelling from A to B or they're not.
In quantum terms: entanglement means they are in both states at the same time, and those states (on & Off or whatever) can't be separated because the quantum particle is in two places at the same time.
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