European team bests Chinese record at teleporting distance (Corrected)

Jun 01, 2012 by Bob Yirka report
Quantum teleportation between the Canary Islands La Palma and Tenerife over both quantum and classical 143 km free-space channels. Image from arXiv:1205.3909v1.

(Phys.org) -- A European team of physicists has bested the record set by a team of Chinese researchers last month for distance in teleporting quantum bits (qubits). Where the Chinese team accomplished their feat by teleporting photons across a lake, the European team did so by performing the same feat across the ocean between two islands off the coast of Africa. It was apparently no easy feat as the team describes in the paper they’ve written and uploaded to the preprint server arXiv; they had so much foul weather to contend with that their experiment took nearly a year to complete. The record breaking distance by the Chinese team was close to 100 kilometers. The Europeans bested that mark by almost fifty kilometers, setting up a possible rivalry between the two teams to see which might be the first to successfully teleport a qubit to an orbiting satellite.

The work done by both teams, and many others across the globe in working out how to use entanglement of of information to achieve a degree of teleportation is not just an exercise to prove that physics theories are correct; if qubits can be sent and read onboard satellites a new age in such communications is likely to be born, one where messages can be sent without worry that they are being decoded by others. That’s because common sense tells researchers that information that is sent instantaneously, without having to actually travel through the air, leaves no means for those that might wish to capture such data.

In their paper, the team says that they had to develop several different techniques to deal with all the noise that occurs when attempting to communicate not just through the air, but air that is volatile. This was made even more difficult by uncooperative weather and sand storms. One of those new techniques might just help pave the way to teleporting qubits much longer distances. They used entangled to synchronize the clocks that were used on both ends of their system to enable them to look at the qubits at both locations at very nearly the same instant in time. Prior to the development of this method, researchers had to rely on GPS synchronization. This new method reduced the event window from 10 nanoseconds to just 3.

The team notes that adapting their technique to teleport qubits to a satellite should be easier in some respects, as there is less noise when trying to teleport straight up as opposed to horizontally through the atmosphere. Of course, there will be the problem of adjusting for the movement of a satellite relative to equipment on the ground, but thus far neither team seems to see that as a problem.

Explore further: Step lightly: All-optical transistor triggered by single photon promises advances in quantum applications

More information: Quantum teleportation using active feed-forward between two Canary Islands, arXiv:1205.3909v1 [quant-ph] arxiv.org/abs/1205.3909

Abstract
Quantum teleportation is a quintessential prerequisite of many quantum information processing protocols. By using quantum teleportation, one can circumvent the no-cloning theorem and faithfully transfer unknown quantum states to a party whose location is even unknown over arbitrary distances. Ever since the first experimental demonstrations of quantum teleportation of independent qubits and of squeezed states, researchers have progressively extended the communication distance in teleportation, usually without active feed-forward of the classical Bell-state measurement result which is an essential ingredient in future applications such as communication between quantum computers. Here we report the first long-distance quantum teleportation experiment with active feed-forward in real time. The experiment employed two optical links, quantum and classical, over 143 km free space between the two Canary Islands of La Palma and Tenerife. To achieve this, the experiment had to employ novel techniques such as a frequency-uncorrelated polarization-entangled photon pair source, ultra-low-noise single-photon detectors, and entanglement-assisted clock synchronization. The average teleported state fidelity was well beyond the classical limit of 2/3. Furthermore, we confirmed the quality of the quantum teleportation procedure (without feed-forward) by complete quantum process tomography. Our experiment confirms the maturity and applicability of the involved technologies in real-world scenarios, and is a milestone towards future satellite-based quantum teleportation.

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Deathclock
3 / 5 (12) Jun 01, 2012
I wish they wouldn't call this "teleportation" because it is not at all what most people would consider the term to mean. Nothing is actually being teleported, not even information.

"By using quantum teleportation, one can ... faithfully transfer UNKNOWN quantum states to a party whose location is even UNKNOWN over arbitrary distances."

antialias_physorg
4.4 / 5 (8) Jun 01, 2012
Argh...first the author of this blurb gets it correct:
one where messages can be sent without worry that they are being decoded by others.

and in the next paragraph he gets it wrong
Thats because common sense tells researchers that information that is sent instantaneously,...


That said: congrats to the teams...and having been to the Canary islands myself I can understand why the experiment took longer than expected (j/k).

Entanglemnt is NOT used to transmit information but to encode/decode it. In encoding/decoding no information is transmitted. There is no 'instantaneous INFORMATION transmission' involved here.
Code_Warrior
5 / 5 (5) Jun 01, 2012
The record breaking distance by the Chinese team was close to 100 meters. The Europeans bested that mark by almost fifty meters

Dear Author, let me fix that for you:
The record breaking distance by the Chinese team was close to 100 kilometers. The Europeans bested that mark by almost fifty kilometers

TheGhostofOtto1923
4.4 / 5 (14) Jun 01, 2012
Entanglemnt is NOT used to transmit information but to encode/decode it.
So:

"They used entangled photons to synchronize the clocks that were used on both ends of their system to enable them to look at the qubits at both locations at very nearly the same instant in time."

-How do you synchronize clocks using entanglement if you at not transporting info?
antialias_physorg
5 / 5 (4) Jun 01, 2012
Synchronisation is the same as decoding/encoding operation in this case (i.e. you want to do something at both ends the same without having to know WHAT exactly it is you are doing only THAT you are doing something).

Information is defined by a-priori knowledge of the meaning of a message by the sender BEFORE transmission while the reveiver only knows the meaning of the message AFTER receiving it.

In the described case the sender doesn't know what he's sending (the state of the entanglement is not known when the photon is being sent at light speeds - only THAT it is entangled. The whole process from creating the signal to reading it is therefore not superluminal). You can't send an entangled entity and AFTERWARDS force one to be in a certain state
If you do that then that won't affect the other one at all. Only a simple measurement will show both are the same. But since you don't know what that measurement will yield beforehand you haven't transmitted information.
Terriva
Jun 01, 2012
This comment has been removed by a moderator.
Terriva
1.2 / 5 (6) Jun 01, 2012
Prior to the development of this method, researchers had to rely on GPS synchronization. This new method reduced the event window from 10 nanoseconds to just 3.
IMO the synchronization of time events with photons entangled at large distance could serve for verification of recent OPERA experiments with "superluminal neutrinos", where the main culprit was supposedly just the GPS synchronization.
wiyosaya
5 / 5 (6) Jun 01, 2012
So if no information is sent, then nothing is teleported?

When objects are sent from one location to another I'll buy this as "teleportation."

Personally, I think the term "teleportation" simply adds journalistic sensationalism to these articles thereby enticing readers to read them.
Tangent2
1 / 5 (1) Jun 01, 2012
Does anyone else have an issue with this:

Thats because common sense tells researchers that information that is sent instantaneously, without having to actually travel through the air, leaves no means for those that might wish to capture such data.


The issue is that they even state that it is not traveling through the air, so why do they go on to say this, which seems to be the exact opposite of what they just said:

In their paper, the team says that they had to develop several different techniques to deal with all the noise that occurs when attempting to communicate not just through the air, but air that is volatile.


If it is not being transmitted through the air, why is the air a factor in this?
antialias_physorg
3.7 / 5 (3) Jun 01, 2012
If it is not being transmitted through the air, why is the air a factor in this?

The entangled photon needs to travel. Interaction with the air can break entanglement (because it is effectively a 'measurement')
TheGhostofOtto1923
3.9 / 5 (15) Jun 01, 2012
Synchronisation is the same as decoding/encoding operation in this case (i.e. you want to do something at both ends the same without having to know WHAT exactly it is you are doing only THAT you are doing something).

Information is defined by a-priori blah...that won't affect the other one at all. Only a simple measurement will show both are the same. But since you don't know what that measurement will yield beforehand you haven't transmitted information.
Nice standard answer but it does not explain how these clocks are synchronized using entanglement, without teleporting info on the state of one clock or the other. Now does it?
Terriva
1 / 5 (5) Jun 01, 2012
since you don't know what that measurement will yield beforehand you haven't transmitted information
When you hear some voices in the neighboring room, you may not recognize their exact source and location, nevertheless some information is still transferred.
Terriva
3 / 5 (2) Jun 01, 2012
In this experiment the speed of quantum information was found higher than 2×10^4 c (published in PhysLett and Nature, so it's definitely peer-reviewed study.)
antialias_physorg
not rated yet Jun 01, 2012
Nice standard answer but it does not explain how these clocks are synchronized using entanglement,

It is an 'entanglement assisted' synchronisation (which isn't the point of the experiment but just an aspect to get better results by narrowing down the window of arrival for the photons for the single photon detectors employed). The way I read it it simply means that a third photon was generated at each creation of entangled photons to synch up the clocks on both ends so that the pairs of photons would be more readily identifiable. I.e. you send out a photon simultaneously with the event via the regular (non entangled) channel and that tells you which femtoscond window is the relevant one for signals from your detector. Basically it helps bring the SNR up over the entire experimental setup.

Full paper here:
http://arxiv.org/...3909.pdf
Oysteroid
2 / 5 (4) Jun 02, 2012
...that won't affect the other one at all. Only a simple measurement will show both are the same. But since you don't know what that measurement will yield beforehand you haven't transmitted information.
Nice standard answer but it does not explain how these clocks are synchronized using entanglement, without teleporting info on the state of one clock or the other. Now does it?

Let me try to explain with a diff.but similar setup: The clocks are synched by a light(laser) impulse from a third source miles (or parsecs if you like) away. The distances are matched so well that the synch pulse arrives at exactly the same moment (with arbitrarily high precision).

In that way, second location knows that the first one just saw the signal too. Instantly. ... Or does it?

What happens if the beam to the first location was blocked by something? What if it was bombed out of existence and us no more? The second location won't have a clue.

So no -it does NOT know that the first
Oysteroid
2 / 5 (4) Jun 02, 2012
cont.: ... that the first location received the synching impulse at all even, much less at the same instant.

Imagine for instance that the first loc is supposed to fire a powerful laser beam at the second the instant it gets the synch signal. The second, prudently, ducks when it sees its own synch signal arrive.

But...will it look foolish if the first failed to fire (jammed) but it still ducked? So much for the info...
TheGhostofOtto1923
3.9 / 5 (15) Jun 02, 2012
Imagine for instance that the first loc is supposed to fire a powerful laser beam at the second the instant it gets the synch signal. The second, prudently, ducks when it sees its own synch signal arrive.
I see you like to make things up. Try reading the arxiv paper and ponder what 'quantum-assisted synchronization' might mean.
Skylax123
not rated yet Jun 02, 2012
The possible rivalry suggested here is actually real and has been in existence for several years. As someone who has worked in those groups, I can tell you that in this field there is always a race for longer teleportation distances, longer quantum memory storage time, higher readout efficiencies, higher single-photon emission rates etc. and whoever sends in the results first wins. This research for example will probably not be published in nature (high impact journal) while the chinese version will be (although they basically used the same methods). The early bird catches the worm:)
One could ask if this is really still research or rather plain engineering?
I think from a research point of view it is interesting to observe entangled particles so distant from each other. We can now improve the limits on how "fast" entanglement collapses (in theory it should be infinite, but who knows?).
Of course making it work with satellites means global quantum communication so that's the real goa
TheGhostofOtto1923
4.4 / 5 (13) Jun 02, 2012
The possible rivalry suggested here is actually real and has been in existence for several years. As someone who has worked in those groups, I can tell you that in this field there is always a race for longer teleportation distances, lon
Without competition nothing would ever get done.
slayerwulfe
not rated yet Jun 02, 2012
to Code Warrior and others i hope we all realize the author is not a part of the team.
Skylax123
5 / 5 (1) Jun 02, 2012
The possible rivalry suggested here is actually real and has been in existence for several years. As someone who has worked in those groups, I can tell you that in this field there is always a race for longer teleportation distances, lon
Without competition nothing would ever get done.

Certainly true in some cases. But from what I have seen it can also have some negative consequences. One example would be that research data is "edited" to better fit the theory because retaking the data would take too long and the first data was wrong because someone spilled coffee over your laser or something (in other words research takes time and with competition you just make it sloppy research).
Anyway look at the LHC, they don't have any competition for their Higgs boson search (the tevatron has been switched off since last year) and still they manage to make good progress. Anyone who needs competition to be productive should maybe think about changing careers, IMHO.
Oysteroid
1 / 5 (1) Jun 02, 2012
I see you like to make things up.

--- TheGhost...

I see you like to emit hot (and smelly) air but avoid the subject.

First, you refused a strict and formal answer provided by others. Then, when I suggested a simplified analogy, you dismiss it out of hand as not fitting with...the above formal issue!

Make up your mind - will anything apart from your own blurb satisfy your stringent requirements for explanation?
Oysteroid
1 / 5 (1) Jun 02, 2012
What I tried to show was a possible answer to your own question of "how these clocks are synchronized... without teleporting info" which doesn't even require quontum synch. Yet, you chose to attack the very method I used to try to bypass your obvious not understanding of the said quantum effects.
TheGhostofOtto1923
4.4 / 5 (13) Jun 02, 2012
Anyway look at the LHC, they don't have any competition for their Higgs boson search (the tevatron has been switched off since last year) and still they manage to make good progress.
Tevatron continued to push them and vice versa. And they did beat out the SSC. And everybody competes for grant money and jobs.
Anyone who needs competition to be productive should maybe think about changing careers, IMHO.
And anyone who does not like healthy competition should maybe think about changing careers IMHO. Yes? No? Although none come to mind offhand.
The second, prudently, ducks when it sees its own synch signal arrive.
Sorry I guess you meant this to be funny? Anyway what does any of what you said have anything to do with 'quantum-assisted synchronization' which IS how it is done per the arxiv paper?
TheGhostofOtto1923
4.3 / 5 (12) Jun 02, 2012
One example would be that research data is "edited" to better fit the theory
I don't know I like to think that the overwhelming majority of scientists are professionals with a great deal of integrity and respect for their professions, and they welcome the energy and inspiration which comes from others just as interested as they are in the process of scientific discovery.

How's that? Uplifting enough? Evolution is nothing BUT competition. This includes evolution of science and technology.
antialias_physorg
not rated yet Jun 02, 2012
I think you have a false conception about science. It's not a race. Groups aren't competing against one another (only in the minds of the PR people and the media does that ever happen). The stuff that groups work on may look similar - but it almost never is exactly the same. So each group works (and publishes) on different aspects of things (and the successes of one group do in no way affect the grants situation or project plans of another. Small exception would be when both groups apply for the same grants...which isn't the case for the Tevatron and the LHC).

Science also isn't a 'hire and fire' situation (science would be neigh undoable if people would only be hired for the duration of a grant/project) - so competition for jobs is also not much of an issue.
TheGhostofOtto1923
4.4 / 5 (13) Jun 02, 2012
I think you have a false conception about science. It's not a race. Groups aren't competing against one another (only in the minds of the PR people and the media does that ever happen).
And I think you are a little naive as usual. The military is a good example. They will often opt to fund 2 or more versions of a weapons system (F16 vs F20 zum Beispiel) in order to keep overall costs down and the final product of the best quality.
Science also isn't a 'hire and fire' situation (science would be neigh undoable if people would only be hired for the duration of a grant/project) - so competition for jobs is also not much of an issue.
Sure it is. Plenty of competition for grant money. Politicians and university benefactors want to see tangible results with big-ticket projects, especially today. University depts compete for limited funds which is a good thing.

Plenty of people lost their jobs when SSC was terminated. Plenty were cut when fusion fell out of favor.
Au-Pu
1 / 5 (1) Jun 02, 2012
They didn't "bested" the Chinese. They beat or surpassed the Chinese. Does illiteracy pervade all levels of US society?
kaasinees
3.7 / 5 (3) Jun 03, 2012
Go Europe, our last line of defense against capitalism.
antialias_physorg
not rated yet Jun 03, 2012
They will often opt to fund 2 or more versions of a weapons system (F16 vs F20 zum Beispiel) in order to keep overall costs down and the final product of the best quality.

Yeah...Like that ever worked out.

And I think you are a little naive as usual.

Seeing as I've 'been and done' I think I know a bit better how this area works. There are a number of people who do and manage research. The managing guys are usually the profeesors (who have tenure - so they can give fuck all about whether they get grants or not).
Then there are the postrdocs whose positions are more or less secure as they cost very little. They are being paid throughthe department budget. Being aspiring professors they do research and some management.

Then there are the grad students (who cost next to nothing). Their positions are mostly paid by grant money...
antialias_physorg
not rated yet Jun 03, 2012
... they do most of the actual research. Their positions are limited to 2 to 5 years (until the finish their PhD) at which time they usually go to work for the industry or, if there is an opening and they are really good, they can get one of the postdoc positions.

So at no time is there a situation where someone could be fired because a grant doesn't come through. Universities also try for cooperations with the industry to get money for research that way (which is a mixed blessing, since such cooperations usually demand immediately applicable results which leads to very low level science).

The 'big ticket' projects have their funding worked out in advance.
TheGhostofOtto1923
4.4 / 5 (13) Jun 03, 2012
Yeah...Like that ever worked out.
?? The F16 is the best austere fighter ever built. The tigershark was also a damn fine plane according to chuck yaeger.
so they can give fuck all about whether they get grants or not).
?? Tenure is often conditional on things like the ability to publish. What do you do with a tenured prof whose Dept is eliminated?
So at no time is there a situation where someone could be fired because a grant doesn't come through.
Your hypotheticals do not reflect real-world conditions. In other words you are naive. Dont worry I am sure it is willful.
antialias_physorg
not rated yet Jun 03, 2012
Well, as I sadi: since I've actually worked as a scientist on more than one occasion and in more than one setting (university and also a private research company)...

... but actual experience is certainly no match for hear-say, I'm sure (/sarcasm)
TheGhostofOtto1923
4.4 / 5 (13) Jun 03, 2012
The effects of competition and the real world on tenure:

"The period since 1972 has seen a steady decline in the percentage of college and university teaching positions in the US that are either tenured or tenure-track. United States Department of Education statistics put the combined tenured/tenure-track rate at 56% for 1975, 46.8% for 1989, and 31.9% for 2005. That is to say, by the year 2005, 68.1% of US college teachers were neither tenured nor eligible for tenure; a full 48% of teachers that year were part-time employees."

-Your heresay typicals are unfortunately atypical.
TheGhostofOtto1923
4.4 / 5 (13) Jun 03, 2012
Well, as I sadi: since I've actually worked as a scientist on more than one occasion and in more than one setting (university and also a private research company)...
I have worked for an ivy league university on a DOE-funded fusion research project, and also in direct support of scientists at major corporate research and production facilities my entire professional career. PLUS I know how to use google.

What else ya got Auslander?