Author Topic: Instantaneous Distant Communication via Quantum Entanglement  (Read 17972 times)

Offline sanman

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Scientists are claiming to have demonstrated "reliable" quantum communication:

http://www.nytimes.com/2014/05/30/science/scientists-report-finding-reliable-way-to-teleport-data.html

I'd always read that while quantum communication is possible, it was so inherently unreliable that any information transmitted by this means would always have to be verified by a classical channel, thus making it rather useless or redundant.

However, if this communication could be done with a high degree of certainty and reliability, perhaps it could become useful.

Is such communication possible, and if so, could it enable new advances in space telecommunications across vast distances?

Online QuantumG

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Umm.. shouldn't you be telling us what this has to do with space? It's your thread.
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Offline sanman

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Well, it seems that telecom drives the space launch sector, and secure quantum communications can help the telecom market, and thus indirectly the space launch industry.

I was reading this:

http://www.sciencemag.org/content/early/2014/05/28/science.1253512

Quote
Realizing robust quantum information transfer between long-lived qubit registers is a key challenge for quantum information science and technology. Here, we demonstrate unconditional teleportation of arbitrary quantum states between diamond spin qubits separated by 3 m. We prepare the teleporter through photon-mediated heralded entanglement between two distant electron spins and subsequently encode the source qubit in a single nuclear spin. By realizing a fully deterministic Bell-state measurement combined with real-time feed-forward quantum teleportation is achieved upon each attempt with an average state fidelity exceeding the classical limit. These results establish diamond spin qubits as a prime candidate for the realization of quantum networks for quantum communication and network-based quantum computing.

Hmm - "fully deterministic Bell-state measurement" - I thought that phrase was an oxymoron.


http://www.cnet.com/news/scientists-achieve-reliable-quantum-teleportation-for-the-first-time/

The details of this experiment seem to involve diamonds brought to near absolute zero, enabling the states of trapped electrons to be read with greater precision.

It seems as if the more we push matter/energy to extreme fringe states (eg. nitrogen atoms pinned inside rigid diamond molecular lattices near absolute zero) then the more we're able to challenge physical limits in other domains.



Offline TomH

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This article is written for an audience without a physics background, so it may seem fluff. Nevertheless, the author reports on progress by Dutch physicists in sending information via quantum entanglement which was successful on 100% of their attempts.

This is similar to the earliest research with radio waves. Advanced communications devices based on quantum entanglement could potentially allow instantaneous two way communication and control between any two points in the entire universe. It has no relationship to teleportation of matter (sorry, Scotty will not yet be able to beam you up), however it could allow real time control of Mars rovers or Europa submarines from Earth.

http://time.com/2800071/teleportation-quantum-entanglement/

Online QuantumG

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Unless, ya know, they redefined the laws of physics while I wasn't looking, I think this is a great example of failed journalism.

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Offline TomH

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Whoops, started a new thread on this and then noticed someone had beat me to it, so I am moving the post to here. QuantumG, your inquiry is answered below:

This article is written for an audience without a physics background, so it may seem fluff. Nevertheless, the author reports on progress by Dutch physicists in sending information via quantum entanglement which was successful on 100% of their attempts.

This is similar to the earliest research with radio waves. Advanced communications devices based on quantum entanglement could potentially allow instantaneous two way communication and control between any two points in the entire universe. It has no relationship to teleportation of matter (sorry, Scotty will not yet be able to beam you up), however it could allow real time control of Mars rovers or Europa submarines from Earth.

http://time.com/2800071/teleportation-quantum-entanglement/




Offline TomH

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Well, I'm sorry but this has been well known within quantum physics for quite some time. I hate to tell you, but this has been known since Einstein was alive, and he himself was aware of it. Quantum physics does not work the same way as physics at our level or the astrophysical/cosmological level. Have you not heard of the search for a unified theory of everything, of the theories of loop quantum gravity vs. string theory, whether the true number of dimensions in our reality is 10 or 11? Time does not exist in the same way at the quantum level. A photon can go out of existence and come back into existence. One single photon can exist in two places at the same time. Time just does not work the same way at the quantum level. Particles that become entangled are connected at the sub-space level. You manipulate one and the entangled particle, no matter how far away, reacts in like matter instantaneously. It doesn't matter if it is on the far side of the universe.

This is not fiction. It is fact. It is quantum physics, and the property is known as quantum entanglement. Don't take my word for it. Go do the research.

Online QuantumG

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Quantum entanglement does not imply instantaneous communication. This is physics 101.
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Offline bubbagret

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"According to the formalism of quantum theory, the effect of measurement happens instantly. It is not possible, however, to use this effect to transmit classical information at faster-than-light speeds (see http://en.wikipedia.org/wiki/Faster-than-light#Quantum_mechanics)."

Offline savuporo

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Particles that become entangled are connected at the sub-space level. You manipulate one and the entangled particle, no matter how far away, reacts in like matter instantaneously. It doesn't matter if it is on the far side of the universe.

This is an awesome property, and it is very unfortunate that this mechanism alone is completely useless for transporting information.

However, this might work
http://www.smbc-comics.com/?id=3371#comic
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Offline TomH

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The article is reporting progress made by the Dutch researchers. The fact that we currently are not able to transmit classical information does not rule out the possibility that we may in the future be able to manipulate entangled particles in a manner that does allow that.

Online QuantumG

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Yeah, it does.

This isn't some technical quandary that will be overcome next week. If faster than light communication becomes possible, it will be new physics, not quantum entanglement.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline savuporo

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Offline ChrisWilson68

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Don't feel bad TomH, it's a common misconception that quantum entanglement can allow faster-than-light communication.  But the other posters are right, quantum theory definitely says it's not possible to use quantum entanglement to transmit information faster than light.  Quantum theory has to be replaced by some other theory if you want faster-than-light information transmission.

Offline Darkseraph

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I'm sure it can be used to instantaneously transmit popular misconceptions about quantum physics!
"For a successful technology, reality must take precedence over public relations, for Nature cannot be fooled." R.P.Feynman

Offline IRobot

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Yeah, it does.

This isn't some technical quandary that will be overcome next week. If faster than light communication becomes possible, it will be new physics, not quantum entanglement.
Not new physics. String theory can explain that. You seem to be travelling at faster than light speed in 3 dimensions, while in reality you are travelling slower than light speed between two points through the extra dimensions.

Quantum theory concept of a particle disappearing and showing up somewhere else can be explained as a particle travelling in a straight path on a +3 physical dimensions medium.

Offline ChrisWilson68

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Yeah, it does.

This isn't some technical quandary that will be overcome next week. If faster than light communication becomes possible, it will be new physics, not quantum entanglement.
Not new physics. String theory can explain that. You seem to be travelling at faster than light speed in 3 dimensions, while in reality you are travelling slower than light speed between two points through the extra dimensions.

Quantum theory concept of a particle disappearing and showing up somewhere else can be explained as a particle travelling in a straight path on a +3 physical dimensions medium.

Actually, no, that's wrong on all counts.

String theory is a theory that gives exactly the same results as standard quantum theory for all the experiments we can do.  The extra dimensions in string theory are very, very, very small and don't let you travel faster than light in our three dimensions.  And, in any event, travelling in other dimensions or not has nothing at all to do with quantum entanglement, which what the quote you're replying to is about.

Offline R7

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No to FTL radio but quantum entanglement is nature's gift to unbreakable encryption. The entangled electrons are one-time pad and you'll notice if unauthorized party tries to access them.

http://en.wikipedia.org/wiki/Quantum_key_distribution
AD·ASTRA·ASTRORVM·GRATIA

Offline Jester

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Ahh my "collegues" at good old T.U Delft !

Unconditional quantum teleportation between distant solid-state quantum bits

http://www.sciencemag.org/content/early/2014/05/28/science.1253512

« Last Edit: 05/31/2014 09:35 AM by Jester »

Offline Nilof

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Well, while superluminal communication is not possible, qbits do have a level of interactivity associated with them.You can set up a superposition so that you can get one set of classical bits from one measurement, a second one from another measurement etc. So if you sent say a billion QBits along with a table of contents, you could easily have billions of different 1 Gb files inside it, and using the table of content you could choose which one you want. For example, sending all articles of wikipedia at once, and the reciever gets to choose "which one was sent".

Sadly, sending lots of correlated QBits with quantum teleportation quickly requires sending massive ammounts of classical information, so making this practical would be difficult. You'd basically have to physically move the QBits, and avoid decoherence along the way.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline IslandPlaya

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I'm afraid you are wrong. You need to transmit information classically to decode the teleported qubits. Its good that there is no need for error correction if what is found is true, but we do not have a means to transmit instantaneously.

Offline Burninate

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'Reliable quantum communication' may be relevant to communications encryption and perhaps computing, but nobody was seriously predicting any ansible-like FTL comms, and those predictions have not come true.

Still can't beat the speed of light.
« Last Edit: 05/31/2014 04:38 PM by Burninate »

Offline Burninate

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Quantum entanglement does not imply instantaneous communication. This is physics 101.
Physics 103, in fact :).

This thread should be merged with http://forum.nasaspaceflight.com/index.php?topic=34854.0

Online RonM

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It has no relationship to teleportation of matter (sorry, Scotty will not yet be able to beam you up), however it could allow real time control of Mars rovers or Europa submarines from Earth.

That would be the end of human spaceflight. If you could real time control robots anywhere in the Solar System, there is no reason to send astronauts. Depending on what side of the human exploration vs. robotic exploration argument you are on is whether or not that is a good thing.

Offline A_M_Swallow

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Application to space.

We cannot transmit information using radio or laser through the sun.  It blocks the beams.  Does the sun block quantum entanglement?

Electromagnetic waves follow an inverse square law.  When the distance doubles the receiver only gets a quarter of the power.  To communicate with say Pluto we need to use very high levels of transmission power, low baud rates, very large dishes and super-cooled antennas.  Information transmission via quantum entanglement may be independent of distance and power levels.  In the future we may get it to work over interstellar distances.

Offline IslandPlaya

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I'm afraid you are wrong. You need to transmit information classically to decode the teleported qubits. Its good that there is no need for error correction if what is found is true, but we do not have a means to transmit instantaneously.
Thru the sun or not. The same applies.

Offline JeanPierre_LeRouzic

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Hello,

I will try sum it up in layman terms, apologies if there are any errors:
Indeed not only entanglement is not instantaneous (or FTL) communication, but it is also indirectly subject to attenuation, because in any cases the entangled states, or information that the entanglement is broken, are propagated classically and therefore are subject to attenuation.
Imagine you are on Earth and want to communicate with a satellite, so you send classically an entangled photon to the satellite and keep the other photon near you. As soon the satellite measures the entangled state on its photon, we can measure the same state on our own.

But the "as soon" doesn't mean much.
We can't know when or even if the measurement was done on the satellite by measuring our own photon, as it would destroy the entanglement, so we have to wait to receive the information that the entanglement was destroyed, by classical means. If you can't receive this information because the satellite is too far, or on the other side of the sun, entanglement is useless.
It could be useful for cryptography, to create what they call a "shared secret" but there are classical ways to share a secret that do not involve transmission at all.

For example if you had a set of cards instead of a pair of entangled photons, and if you split the set in two without looking at which cards you keep. You send the half set to the satellite, instead of sending a photon. Then at anytime later, without even receiving information from the satellite, if you look at the cards in your half set, you *instantly* know which cards are inside the satellite. You now share a secret with the satellite.
« Last Edit: 05/31/2014 10:27 PM by JeanPierre_LeRouzic »

Offline A_M_Swallow

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Hello,

I will try sum it up in layman terms, apologies if there are any errors:
Indeed not only entanglement is not instantaneous (or FTL) communication, but it is also indirectly subject to attenuation, because in any cases the entangled states, or information that the entanglement is broken, are propagated classically and therefore are subject to attenuation.
Imagine you are on Earth and want to communicate with a satellite, so you send classically an entangled photon to the satellite and keep the other photon near you. As soon the satellite measures the entangled state on its photon, we can measure the same state on our own.

But the "as soon" doesn't mean much.
We can't know when or even if the measurement was done on the satellite by measuring our own photon, as it would destroy the entanglement, so we have to wait to receive the information that the entanglement was destroyed, by classical means. If you can't receive this information because the satellite is too far, or on the other side of the sun, entanglement is useless.
{snip}

How about.  The transmitting equipment could be programmed to send the message at a time T.  The receiver can be programmed to examine its photon at time T+1.  This timing information was given to the transmitting equipment by conventional means, just before rather than after the message was sent.

If we are still limited to the speed of light then the receiver can look at its photon at time T+1+x

where x = distance to satellite / speed of light in the same units.

There is uncertainty about whether a message was sent but two parity bits can detect that 3 out of 4 times.

Offline savuporo

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Information transmission via quantum entanglement may be independent of distance and power levels.  In the future we may get it to work over interstellar distances.
The phenomenon of quantum entanglement is unable to transmit information - on its own.

"For every qubit teleported, Alice needs to send Bob two classical bits of information."

EDIT: could someone please edit the title of this thread ? It is wrong. There is no "instantaneous communication" or "instantaneous transport of information" happening.
« Last Edit: 06/01/2014 02:05 AM by savuporo »
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Offline cordwainer

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I would point out that NIST's JQI experiment merely shows that using daughter beams with a single photon would suffer from too much quantum noise to allow intelligible transmission of information. At much larger scales quantum noise could be overridden to allow for a functionally pure gain signal. Without further experimentation quantum communication cannot be ruled out.

Offline Burninate

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Yes, much of science fiction is premised on FTL travel and FTL comms.  The actual physics of the thing is rather a lot harder to learn than you might expect, and is deeply nonintuitive (as is general relativity itself)... but please?  Everyone I know who's studied these things mathematically long enough to have some idea what they're talking about says this is physically impossible, and not impossible like 'hasn't been invented yet', but impossible like 'violates the part of our understanding of the fundamental structure of the universe that has withstood most every test we have thrown at it'.  "Instantaneous distant communication" is a trope that is brought up at *literally every media invocation of entanglement*, that the scientists involved in researching it shout down *every single time*, because journalists are trying to misquote them to promise the public FTL.
« Last Edit: 06/04/2014 01:38 PM by Burninate »

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