Spooky action at a distance
I am covering a recent bit of Science news reported in Nature. It has to do with "spooky action at a distance". I had studied this quantum mechanics phenomena under Prof. Alain Aspect (not kidding you on the name) while at the Polytechnique School in Paris. So when I saw him pen the coverage of the research I was somewhat excited. Prof Aspect is famous for an experiment done in the 80's whose results violate Bell's inequalities and confirm predictions of Quantum Mechanics instead.
First hypothesized by Einstein, Podolski and Rosen, this class of "thought experiment" was about pointing out a weird prediction that spooky action at a distance was predicted with particles in a Quantum state called "entangled". Einstein famously did not believe in this possibility.
Since then, a lot of observed data has dodgedly confirmed the QM predictions to the dismay of many physicists. As Alain Aspect puts it in the "news and view" coverage of the new research in Nature "one has to wonder what a scientist like Einstein would have to say knowing what we know today".
The conumdrum
Special relativity tells us that the speed of light is finite (and constant). Point A and B can communicate exchanging light within the time it takes for that light to travel from point A to point B.
Now, take 2 photons that are entangled, intermingling at a point in time so their quantum state obey a conservation law down the road. Now, the trick is that you let the photons fly apart to a point where they cannot communicate any longer at the time of measurement: A and B are so far apart that they cannot exchange photons in the time it takes to do the measurements. In theory they are separated: that is "locality".
EPR introduced the notion of "hidden variables" take 2 cards, a queen and a king, they are "entangled" if you see a queen you know the other one is a king and vice-versa. So when you let the card "travel" and you observe a "king" it is not because communication took place just because that is what your cards are. That is "realism".
Realism can be translated in a series of inequalities, first derived by Bell that give you measurable quantities. The experiments under discussion violate those inequalities, essentially pointing to 'instanteneous communication" between particles far apart. Are we to believe that information was carried faster than the speed of light? Esentially at once?
Saving both Realism and Locality
Which concept is at fault? Realism or Locality? Locality is a cause of the finite speed of light. The assumption here is "speed of light is finite". Since we observe spin, I assume a "reality" to that dimension. It may be wrong but for all I know, facts agree with this interpretation. Realism starts encompassing more dimensions than the ones we experience and observe as humans (4D: time and space). Expanded realism takes as realm "dimensions" of spin.
In this quantum space, the state of the particles never "drifts" apart, they are entangled, they are physically connected and information exchange can take place in that space. If it does, it may very well obey the laws of locality, i.e finite speed of information.
Furthermore, maybe the laws of locality have no sense at all in the geometry of spin, there is no notion of "space of points" like 3D realism but rather a vectorial space of a quantum variables. Whatever it is, this instant communication, is observed, can we leverage it?
Technical applications?
Aspect calls, towards the end of his article, for a leap to technical applications of the effect. It is a tall order :) If the effect is so pervasive, what is truly exciting is that we have the technology, at least in the lab, to interact with this sub-world.
One application is network communications. If the results above can be scaled from lab distances to span continents, then we have zero latency across vast distances. Zero latency caches would be buildable with such a technology enabling instant and synchronous state. Is this truly valuable in computing? maybe, you tell me! Are there applications that absolutely require zero latency (databases?).
One application could be with clocks or primary key generation. This would be a way to build a master clock that is always synchronized, worldwide. Or a way to assign IDs that are truly guaranteed unique.
It seems however that from that point of view, applications in networking are far fetched for now, after all latency on earth is on the order of 100ms? for intercontinental communication? this is perfectly acceptable for most applications. Again, any class of practical problem that suffers from the presence of latency would get a boost from this technology.
Sci-fi
The benefits of this technology become intuitive when you think about space communication. For those of you that have read "Ender's game" this is how you build the machine that enables instant communication across galaxies. In spite of limited speed of light you can have immediate reach across space from point A to point B. All you need is entangled particles on both ends which implies a source somewhere in the geometrical center, you perform operations on one end and supposedly it affects the particle on the other end, essentially establishing instanteneous information transfer.
So a center emits tangled particles, this is equivalent to a physical link between the two points, say moon and earth, and as soon as a continuous flow of entangled photons takes place, you can start communicating with the other point in real time. You have achieved instanteneous communication in your 3D world, by taking a shortcut through the quantum dimension.
Still in the Sci-fi approach, this result says that Nature has ways of communicating through quantum portals as it where. It has been hypothesized elsewhere that brain cells may contain quantum equipment, both to emit and detect. And that essentially quantum computation is involved in thought. If that is true then the brain cells have built-in technology to interact with the quantum world. It would be cool to harness the proteins and DNA that are responsible for encoding these devices, if they exist. Hijack that code, improve on it, with a rapid evolution design as covered in a previous blog and you have cheap ass, mass manufactured QM equipment.
Like many shamans and whitches have intuitively known in the past, "Spooky action at a distance" is a fact of life, just now do we start having the technology
marcf
First hypothesized by Einstein, Podolski and Rosen, this class of "thought experiment" was about pointing out a weird prediction that spooky action at a distance was predicted with particles in a Quantum state called "entangled". Einstein famously did not believe in this possibility.
Since then, a lot of observed data has dodgedly confirmed the QM predictions to the dismay of many physicists. As Alain Aspect puts it in the "news and view" coverage of the new research in Nature "one has to wonder what a scientist like Einstein would have to say knowing what we know today".
The conumdrum
Special relativity tells us that the speed of light is finite (and constant). Point A and B can communicate exchanging light within the time it takes for that light to travel from point A to point B.
Now, take 2 photons that are entangled, intermingling at a point in time so their quantum state obey a conservation law down the road. Now, the trick is that you let the photons fly apart to a point where they cannot communicate any longer at the time of measurement: A and B are so far apart that they cannot exchange photons in the time it takes to do the measurements. In theory they are separated: that is "locality".
EPR introduced the notion of "hidden variables" take 2 cards, a queen and a king, they are "entangled" if you see a queen you know the other one is a king and vice-versa. So when you let the card "travel" and you observe a "king" it is not because communication took place just because that is what your cards are. That is "realism".
Realism can be translated in a series of inequalities, first derived by Bell that give you measurable quantities. The experiments under discussion violate those inequalities, essentially pointing to 'instanteneous communication" between particles far apart. Are we to believe that information was carried faster than the speed of light? Esentially at once?
Saving both Realism and Locality
Which concept is at fault? Realism or Locality? Locality is a cause of the finite speed of light. The assumption here is "speed of light is finite". Since we observe spin, I assume a "reality" to that dimension. It may be wrong but for all I know, facts agree with this interpretation. Realism starts encompassing more dimensions than the ones we experience and observe as humans (4D: time and space). Expanded realism takes as realm "dimensions" of spin.
In this quantum space, the state of the particles never "drifts" apart, they are entangled, they are physically connected and information exchange can take place in that space. If it does, it may very well obey the laws of locality, i.e finite speed of information.
Furthermore, maybe the laws of locality have no sense at all in the geometry of spin, there is no notion of "space of points" like 3D realism but rather a vectorial space of a quantum variables. Whatever it is, this instant communication, is observed, can we leverage it?
Technical applications?
Aspect calls, towards the end of his article, for a leap to technical applications of the effect. It is a tall order :) If the effect is so pervasive, what is truly exciting is that we have the technology, at least in the lab, to interact with this sub-world.
One application is network communications. If the results above can be scaled from lab distances to span continents, then we have zero latency across vast distances. Zero latency caches would be buildable with such a technology enabling instant and synchronous state. Is this truly valuable in computing? maybe, you tell me! Are there applications that absolutely require zero latency (databases?).
One application could be with clocks or primary key generation. This would be a way to build a master clock that is always synchronized, worldwide. Or a way to assign IDs that are truly guaranteed unique.
It seems however that from that point of view, applications in networking are far fetched for now, after all latency on earth is on the order of 100ms? for intercontinental communication? this is perfectly acceptable for most applications. Again, any class of practical problem that suffers from the presence of latency would get a boost from this technology.
Sci-fi
The benefits of this technology become intuitive when you think about space communication. For those of you that have read "Ender's game" this is how you build the machine that enables instant communication across galaxies. In spite of limited speed of light you can have immediate reach across space from point A to point B. All you need is entangled particles on both ends which implies a source somewhere in the geometrical center, you perform operations on one end and supposedly it affects the particle on the other end, essentially establishing instanteneous information transfer.
So a center emits tangled particles, this is equivalent to a physical link between the two points, say moon and earth, and as soon as a continuous flow of entangled photons takes place, you can start communicating with the other point in real time. You have achieved instanteneous communication in your 3D world, by taking a shortcut through the quantum dimension.
Still in the Sci-fi approach, this result says that Nature has ways of communicating through quantum portals as it where. It has been hypothesized elsewhere that brain cells may contain quantum equipment, both to emit and detect. And that essentially quantum computation is involved in thought. If that is true then the brain cells have built-in technology to interact with the quantum world. It would be cool to harness the proteins and DNA that are responsible for encoding these devices, if they exist. Hijack that code, improve on it, with a rapid evolution design as covered in a previous blog and you have cheap ass, mass manufactured QM equipment.
Like many shamans and whitches have intuitively known in the past, "Spooky action at a distance" is a fact of life, just now do we start having the technology
marcf
Comments
Actually, that's not how I understand it works (but I'm not a quantum physicist).
You have two particles, A and B, that are maximally entangled (so essentially A == B).
You move them some arbitrary distance away (longest verifiable distance today is 89 miles between the islands of La Palma and Tenerife in the Canaries). That's the first obstacle for inter-galactic communication -- it will take million or billion light years to move the particles apart, since to entangle them they need to be together in the same physical location.
The second thing is (and this is how I understood it) that for this to work there's actually a third particle, particle C, that first interacts with A. Then the particle C is transferred (subject to speed of light!) to B and interacts with B causing a state change. Now this state change appears to happen instantly on the entangled counterpart A (since A == B). The instant nature of the entanglement is a mystery indeed, but it currently takes the physical transfer of particle C to make this happen.
So no zero latency network there -- information transfer is still subject to special theory of relativity, unless you can improve on Einstein's model.
I suppose one could imagine a system which allows you to control the point in time where your latency occurs, by transferring a stream of particles C and storing them until interacting with AB "instantly". You could do this until you "run out of battery" (that is, particle C's). The problem there I think is maintaining the quantum state of particle C that is subject to interference from its environment.
Anyway, apparently this stuff is still good for crypto -- uncrackable to the man-in-the-middle attack (since you can't measure spin without changing it). Unfortunately, not as exciting as truly instant messaging or building Stargates :-)
The class of experiment I described was the one I studied under Aspect. They involved 2 photons, not 3. I am not familiar with the 3 photon experiments.
The effects of entanglement are observable with 2 particles. Which rules out the physical communication you point out.
On the other point you make, you are correct that in order for this effect to happen you need to have two physical photons travel to A and B in the first place and that this phenomena happens at the speed of light at the most.
See where I talk about "Source at the geometrical center" in the text. The point about the center being geometrical is that you need to deal with General relativity in which case the trip from point A to point B is a straight line through a very twisted space if that makes any sense. Gravity will deform the path of a photon.
So imagine that as you explore space you create a grid of repeaters of these entangled photons. There are like the grid for "space". I completely agree with you that establishing "physical connection" meaning the tap is open between 2 points can happen at most at the speed of light.
But the point is that once that flow is established you can start communicating in real time by just using that flow. The effects of one detector that observes photon A are seen immediately at point B.
The article you point out is very interesting. The authors seem to be the same guys from Vienna?
It is interesting that the notion of "teleportation" is a lot more attractive than "information transfer" which we already do with computers :)
Can we leverage that?
In the two photons experiments, the spin orientation of the observers is completely random at both point A and B. Can you leverage this and use the A detector orientation as bit of information to send information to B instanteneously? If not we are wasting time.
If in order to make sense of the A bit at B you need information about the A bit, then you might as well use existing grib based technology to pass that bit around. Yah it's called the internet :)
If the new result about scaling up the distance is coming out on Nature as I saw in one of the reports (btw saw the /. thread you reference) I will receive it and I will dig some more :)
you need information from both points, the configuration of the detection
Essentially, we know today that entanglement seems to happen in real time and is ruling out all "hidden variable" theories.
Can we leverage that?
No clue.
But since spooky action appears to happen without hidden variables then we can be sure there are infinite number of theories as to why entanglement works.
A veiled reality of determinism that denies us our free will?
Or particle sized worm holes?
;-)