Teleported by electronic circuit: Physicists 'beam' information

Aug 14, 2013

ETH-researchers cannot "beam" objects or humans of flesh and blood through space yet, a feat sometimes alluded to in science fiction movies. They managed, however, to teleport information from A to B – for the first time in an electronic circuit, similar to a computer chip.

Physicists at ETH Zurich have for the first time successfully teleported information in a so-called solid state system. The researchers did it by using a device similar to a conventional computer chip. The essential difference to a usual computer chip is that the information is not stored and processed based on the laws of , but on those of . In a study, which is published in the current issue of the scientific journal Nature, the researchers were able to teleport information across a distance of about six millimeters, from one corner of a chip to the opposite one. This was shown to be possible without transporting the physical object carrying the information itself from the sender's to the receiver's corner.

"Usually, in telecommunication information is transmitted by . In mobile communications, for example, are used, while in fiber connections it is ," explains Andreas Wallraff, Professor at the Department of Physics and head of the study. In contrast, quantum teleportation does not transport the information carrier itself, but only the information. This is possible due to the quantum of the system, in particular the established between the sender and the receiver. For non-physicists, entanglement constitutes a "magic" link between the two parties which exploits the laws of quantum physics.

"Like beaming"

As a prerequisite for , an is created between the sender and the receiver. After that the two parties can be physically separated from each other while preserving their shared entangled state. In the present experiment the physicists program a bit of into their device at the sender. Because the two parties are entangled, this information can be read out at the receiver. "Quantum teleportation is comparable to beaming as shown in the science fiction series Star Trek," says Wallraff. "The information does not travel from point A to point B. Instead, it appears at point B and disappears at point A, when read out at point B."

High data rates

The distance of six millimeters over which the ETH Zurich-researchers have teleported seems to be short in comparison with other teleportation experiments. A year ago, for example, Austrian scientists managed to teleport information by more than one hundred kilometers between the Canary Islands of La Palma and Tenerife. That and other similar experiments, however, were fundamentally different from the one performed at ETH Zurich, because they use visible light in an optical system for teleportation. The ETH-researchers, however, managed to teleport information for the first time in a system which consists of superconducting electronic circuits. "This is interesting, because such circuits are an important element for the construction of future quantum computers," says Wallraff.

Another advantage of the system of the ETH-scientists: It is extremely fast and much faster than most previous teleportation systems. In this system approximately 10,000 quantum bits can be teleported per second. A quantum bit is a unit of quantum information.

"Key future technology"

In a next step, the researchers plan to increase the distance between sender and receiver in their device. The scientists say, they will try to teleport information from one chip to another. And in the long term the goal will be to explore whether quantum communication can be realised over longer distances with electronic circuits, more comparable to those achieved today with optical systems.

"Teleportation is an important future technology in the field of quantum information processing," says Wallraff. For example, it may be possible to transmit information from one location to another one in a future quantum device or processor. Compared to today's information and communication technologies, which are based on classical physics, quantum information processing has the advantage that the information density is much higher: In quantum bits more information can be stored and more efficiently processed than in classical bits.

Explore further: Popper's experiment realized again—but what does it mean?

More information: Steffen L, Salathe Y, Oppliger M, Kurpiers P, Baur M, Lang C, Eichler C, Puebla-Hellmann G, Fedorov A, Wallraff A: Deterministic quantum teleportation with feed-forward in a solid state system. Nature, 2013, 500: 319-322, DOI: 10.1038/nature12422

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1 / 5 (2) Aug 14, 2013
I know I am missing something important here. But in answering to this post, I am sending data, what, 6000 miles via some form of data transfer that an awful lot of people use.

1 / 5 (8) Aug 14, 2013
"Usually, in telecommunication information is transmitted by electromagnetic pulses…. explains Andreas Wallraff, Professor at the Department of Physics and head of the study. In contrast, quantum teleportation does not transport the information carrier itself, but only the information. This is possible due to the quantum mechanical properties of the system, in particular the entanglement established between the sender and the receiver. For non-physicists, entanglement constitutes a "magic" link between the two parties which exploits the laws of quantum physics.

Actually we know that even in a real magic show, it is not something which could not understandable, dear professor would you please explain how does it work? Is it possible to be something like this…

not rated yet Aug 14, 2013
There's really nothing magic to it. Suppose a particle decays into a spin up and spin down particle. But you don't know which is which. If you measure yours to be up, you know that the other should be down. It's basic conservation properties.

For more details read the r/askscience thread: http://www.reddit...quantum/
4.7 / 5 (6) Aug 14, 2013
While they are transmitting a state correlation this isn't information transmission because they don't know which way they entangled the two particles beforehand (if they did the would have to measure them - breaking the entanglement in teh process).

The definition of information demands, however, that one know a-priori what message is being sent before sending it. They have a-posteriori correlation...which is only half of what information transmission entails.

Can't have your cake and eat it, too.

3 / 5 (2) Aug 14, 2013
maybe I'm misunderstanding your comment antialias, but it seems from their abstract that they are transmitting information. The way in which quantum "teleportation" messaging is performed allows for you to carry information between two sites without having measured the states of either one particle in the middle. It's a fairly well established procedure that's reasonably well explained in the example of particles of spin-1/2.

1 / 5 (4) Aug 14, 2013

The way to solve that problem is to use two qubits, A and B, which are the same.

When you want to send a "1" you make a change in Qubit A. The "reader" checks both qubits on his end. If they are different then a "1" has been sent. If they are the same, then a "0" has been sent.

So yes, you can send information even without actually knowing the initial states of the qubits, as long as you can prove they are the same. The presence of a "difference" between the object qubit and the reference qubit will prove an intentional piece of data has been sent.
1 / 5 (2) Aug 14, 2013
So they managed to send information faster then the speed of light. Why is this not on TV? :)
3.5 / 5 (2) Aug 15, 2013
10,000 bits of information per second? For how long can this rate of transfer be sustained?

They have to entangle q-bits, move them to separate reservoirs, then transmit. Since the number of q-bits they appear to be working with is 'one pair,' after one transmission, they've depleted the system. It seems that they arrived at their transmission speed by measuring how long it took for the system to effect the transfer of one bit of information: 1/10,000 of a second. But the transfer rate can be sustained for exactly 1/10,000 of a second. Then it's done.

I think the claim that their system is capable of transmitting 10,000 bits per second is terribly misleading.
1 / 5 (1) Aug 15, 2013
Conventional computing requires some sort of interconnecting BUS between chips. This system is hoping to eradicate the BUS completely by teleporting the quantum states. So in the first chip you may do some sort of quantum calculation, then want that result BEAMED to another chip which may do the actual decoding of the result. Seems brilliant to me.
1 / 5 (2) Aug 15, 2013
I have generated an electron-condensate in my laboratory within which the electrons lose their distinguishability as required that they must do according to elementary quantum statistics.

When I inject an electron on one side into this condensate, an electron is ejected on the other side within a time interval that is shorter than the time it would take the injected electron to reach the other side at the speed of light.

Thus, it is possible to teleport information faster than the speed of light. The injected electron loses its distinguishability and the condensate must eject an electron near-instantantaneously to maintain its energy.

This is the simple mechanics of matter waves which have been in our textbooks for nearly 100 years, but has been ignored owing to the Voodoo concepts of "wave-particle duality" and "complementarity".
3 / 5 (2) Aug 15, 2013
When you want to send a "1" you make a change in Qubit A.

A change in one qbit (once the entangled entities have been moved to separate locations) does not change the other one. This only breaks the entanglement.
Entanglement only means that if you measure X to be thus then Y will be in a conjugate state with some correlation factor if, and ONLY if, X and Y were entangled AND neither X an Y have been disturbed since.

Your "change in qbit A" is such a disturbance and invalidates the entanglement. In short: you cannot 'force' one entangled entity to a state and then expect the other one to comply. That's not how it works.

It is, however, useful to have a system as they describe because you can do synchronising tasks very well with it.
5 / 5 (1) Aug 15, 2013
So they managed to send information faster then the speed of light.

I got 1 rating, but my question is serious. Can they claim it, or I'm missing something?

In the nature article they say that:
"As a consequence the receiver's qubit Q3 is projected instantaneously and without ever having interacted with the sender's qubit Q1 onto a state"
1 / 5 (2) Aug 15, 2013
AP knows the difference between information transmission (classical) and information transfer (QM). The distinction is made to maintain a contradiction-free interpretation or description when and where the classical is no longer applicable.
A nonphysical carrier is no longer 'tangible' physics.
AP notes correctly synchronization. To ascertain if events are synchronized still requires the time unimpeded light travels.
3.7 / 5 (3) Aug 15, 2013
It's a tricky business about what is information and what isn't.

When we (colloquially) talk about information transmission we mean the transmission of a message. I.e. something that is known (and presumably has a meaning) at the origin BEFORE you send it and that will then be the same at the receiving end.
The message is therefore something that is encoded on a carrier in a KNOWN state, transmitted, and then read.

In quantum teleportation you have an instantaneous transmission of a state correlation. This means that if I measure the state of entangled entity X I will know something about the state of the entangled entity Y.

When I entangle X and Y I don't know their respective states (i.e. I do NOT have something encoded on a carrier in a KNOWN state).
A subsequent CHANGE to X will not affect Y. So you also can't encode a meaningful message once the entangled entities are separated (well, you can: but it won't be transmitted to Y)
3 / 5 (2) Aug 15, 2013
To put this in 'math' parlance:

Colloquial information transmission concept:
1) a priori knowledge of message at the sender
2) a posteriori knowledge of decoded message at the receiver
3) correlation between 1) and 2) (preferrably full correlation - but not totally necessary for useful information transmission)

QM information transmission:
1) NO a priori knowledge of state but only a POSTERIORI decoding of state at sender
2) a posteriori decoding of state at receiver
3) correlation between 1) and 2) (preferrably full correlation - but not totally necessary for useful QM information transmission)
1 / 5 (2) Aug 15, 2013
Today's physics maintains a description labeled indistinguishable states. A simple label to state the description is necessary, insufficient and incomplete.
5 / 5 (1) Aug 15, 2013
Here is the paper:
3.5 / 5 (2) Aug 15, 2013
Thanks for the link. They have a perfect (and very succinct) summation of quantum teleportation in section II:
Quantum teleportation describes the process of transferring an unknown quantum state between two parties at two different physical locations making use of the nonlocal correlations provided by an entangled pair shared between the two and the exchange of classical information

I'd like to draw attention to the word 'unknown'.
1 / 5 (2) Aug 15, 2013
Yes. I second the appreciation of the link, the perfect summation and focus on the 'unknown'.
Which I labeled as an incomplete, necessary and insufficient description - a state without a carrier is magic.
1 / 5 (1) Aug 18, 2013
For more quantum background info published in 1999.

5 / 5 (1) Aug 20, 2013
I look forward to space traveling probes and robots that can communicate in real time with earth, regardless of the distance they have traveled.

No more really long distance charges and much faster service.
not rated yet Aug 20, 2013
At last, an end in sight for the tyranny of the Telcos. They're worse than CHOAM.

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