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"Spooky" Science Points Towards Quantum Computing
Stony Stevenson writes to tell us that University of Michigan physicists have been able to establish an "entanglement" between two atoms trapped more than a meter apart in different enclosures using light. This shows how two different atoms can have a sort of communication, something Einstein referred to as 'spooky action-at-a-distance'. "By manipulating the photons emitted from each of the two atoms and guiding them to interact along a fibre-optic thread, the researchers were able to detect the resulting photon clicks and entangle the atoms. Professor Monroe explained that the fibre-optic thread was necessary to establish entanglement of the atoms. But the fibre could be severed and the two atoms would remain entangled, even if one were 'carefully taken to Jupiter'."
My arm-chair understand of Entanglement suggests that it should violate causality. Consider the following thought experiment.
We have two pairs of quantum mechanically entangled electrons. We sent a single electron from each pair five light minutes in to space. A long with a small machine that measures that's designed to react when it an electron comes "de-entangled". When it senses this, it immediately the spin of the electron in the other pair.
Here on earth we have a Tsar Bombe linked to one of the electrons from one of the pairs. Five meters away, the other electron is linked to a button. When a person presses the button, it measures one of the electron, thus breaking its entanglement. That instantly breaks the entanglement of the other electron live light minutes away. The machine then breaks the entanglement of the other pair thus instantly triggering the Tsar Bombe destroying the hut and everything in 100 Sq miles.
The problem is that, as I understand it, this would happen ten minutes before I press the button. Whoops! You see, when I de-entangle the first electron the disentanglement on the other side happens five minutes in my past. When the machine disentangles the second electron, the other electron is five minutes in its past. Totalling to ten minutes. Can you see what I'm getting at? I'm assuming this argument isn't new - What mistake have I made here?
Simon.
I've always wondered if we would one day be able to use entangled photons to peer beyond the event of a black hole. Keep one particle in an observable state and send one through the black hole. Something is bound to happen and it might give us some insight into what exists beyond the event horizon. This experiment sounds like a step toward that possibility.
Getting a girl the nerdy way: holding a fiber-optic wire between the two of you and say "Now we're entangled on the atomic level, love me forever!"
Quantum computers, sure. Quantum Internet? Drop the crack pipe and back away from the keyboard!
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
Is this entanglement a means of instant communications across vast distances? Faster than light information transfer?
Dumb it down for me, a simpleton without a background in Quantum Mechanics.
Dominant Meme
An ansible is a device described in science fiction for superluminal communication. It's usually portrayed as a pair (or more) of devices closely connected, as if separated from a common origin.
I'm looking forward to a day when ansible devices are as common as symmetric key crypto, which will likely be the only way to secure their communications, other than the "conservation of info" already built in to quantum entanglement.
--
make install -not war
That's kinda what it sounds like to me anyway... but I'm not all that knowledgeable in the area of quantum physics... I barely understand common physics. But at least I read the article... and it sounds like they have created the atomic equivalent of two cans and a string without the string.
But the fibre could be severed and the two atoms would remain entangled, even if one were 'carefully taken to Jupiter'."
Probably not.
500 dollar reward for tip(s) leading to the arrest of the person(s) who stole my sig.
if I read the article correctly, the fact that they managed to entangle the particles at a macroscopic distance.
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I took the new bit to be the fact that they had entangled atoms.
No folly is more costly than the folly of intolerant idealism. - Winston Churchill
I don't have a great deal of understanding of advanced physics, so I'll throw this out. Could extra dimensions as proposed by string theory help explain this type of stuff?
Except for ending slavery, the Nazis, communism, & securing American independence, war has never solved anything.
Windows locks up when I'm not even touching it ;-P
Table-ized A.I.
To receive a signal you have to measure something. That can be ones and zeros streaming from a wire or light scattering off a distant smoke signal. To make a measurement you have to collapse the wave function. Once the wave function is to more, you have no chance of sending anything else. So maybe we could send a single bit with a single entangled state. Perhaps the trick would be to get a whole lot of them. The fact that the universe is self consistent lends credibility to causality.
With a quantum communication device you can transmit your status and location from underground to help above. This will also revolutionize space exploration via mechanical avatars controlled by quantum communication. (HD Instant images and tactile feedback)
- Yes, I am posting at a -1, and no I will not use a proxy to bypass my circumstances.
I predict this could very well be the beginning of the end for submarine and coast-to-coast fibre hauls in fact all fibre. Think about the possibilities, you could hook up remote islands with fibre-like connectivity too, by transporting these entangled photons to remote datacenters.
I believe the article said " carefully taken to Jupiter" so that rules out UPS, FedEx, and especially the post office...
-=Geoskd
I wish I had a good sig, but all the good ones are copyrighted
probably true. i'm almost certain i've read that there was a successful experiment at a distance of around 10 or 11 kilometers, but with electrons or photons.
> something Einstein referred to as 'spooky action-at-a-distance'.
I could have sworn my therapist used those exact words when describing my sex life.
Every time somebody tracks a package online, there's a 50% chance that a cat somewhere dies.
We should probably not use words like "communication" to describe entanglement, because it only confuses people. Connection and correlation do not equal classical communication.
why is "appalachianstate" a tag? the article mentions nothing about it....
http://kered.org
1. Entangle two atoms
2. Transport one of them to Jupiter (Or your favorite planetary body, Pluto excluded)
3. Detonate a bomb at the other atoms location
4. ???
5. PROFIT!
Do not meddle in the affairs of dragons, For you are crunchy and go well with ketchup.
FLASH used exactly that concept, and it lead to the discovery of the fact that there can be no quantum cloning. It was hypothesized that it was possible to tell whether an electron (or any other particle) was entangled or not, basically by seeing if a measurable property changed when another entangled property was measured. It relied on being able to make a perfect copy of the quantum state and measuring it repeatedly to get exact measurements in violation of the uncertainty principle. If that could be done, then measuring an entangled particle would transmit measurable information to the other entangled particle(s) immediately. It turns out that perfect (100% accurate) quantum cloning is not possible, so no matter which particle gets measured first there's no way to tell on the other end. It's interesting that the actual limit on the probability of success in quantum cloning (which has been measured physically and found to match the predicted value well) is exactly the limit necessary to prevent causal inconsistencies or faster than light information transfer.
Good news everyone!
"I only speak the truth"
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I thought they had entangled atoms before also. Given the other reply to you post, maybe it's the combination of atoms and macroscopic distance?
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The professor who did this research is from UMich and the Michigan Football squad was humiliated in a loss to Appalachian State. It has become a bit of a joke to the point where people who had never even heard of Appalachian State (even Michigans own fans) are buying App State T-shirts with the express purpose of wearing them at University of Michigan football games.
The two events aren't really connected aside from involving UMich. Welcome to popular culture.
I think the invisible hand of the market has its middle finger extended
--A wise old fart named SC0RN
The distant particle that crosses into the block hole will break entanglement when it is altered or destroyed, but nothing will happen to your particle, so you'll still know nothing. You won't even know that it is became disentangled since nothing will change on your side.
Excuse me, but please get off my Pennisetum Clandestinum, eh!
The "faster than the speed of light" thing surprises me. Not because of how c functions in relationship to matter and energy, but because the physicists, whose discipline has now had a full 100 years to digest these complexities, and personally, eight or more years of post-secondary education hammering home the need to state things carefully, fail to state that the fact of the violation of the speed of light for an effect can not itself be established at faster than the speed of light.
Two physicists in a similar reference frame measure two entangled particles in different light cones (any interaction would therefore need to travel faster than ligth). The entanglement effect says that if one measures red, the other measures blue. How do they confirm this? The information about their measurements must travel *at the speed of light* until information from the distinct measurements meets up. At *this point in time* they know if the entaglement effect conformed with theory or did not conform with theory. They can't posssibly determine this conclusion faster than the speed of light between the positions where the measurements were taken.
It interests me that the effect can travel faster than light, but the conclusion about the effect can not, yet I've never seen a physicist discuss this. The discussion always goes entanglement, faster than light, spooky, bada bing. It's possible that the entanglement effect doesn't resolve itself until information about the two experimental measurements (which converges in obedience with the speed of light) actually meets up. Perhaps the disentanglement takes place only *after* the results of the two experiments meets up. That would involve the experiment (and experimenters) having become entangled in the experiment. Weird? In the realm of the very tiny, that's never stopped mother nature before.
On a related point, I've never seen a physicist comment on whether it is possible to take two particles of unknown histories and prove they are not entangled. I suspect this can only be done by taking measurements which shuffle the quantum deck. Entangled particles are always introduced as an exceptional state of matter, produced painstakingly only in laboratory equipment for the purpose of conducting this experiment.
Is it not possible that most of the particles in the universe are entangled with most of the other particles of the universe? If there is no physical demonstration that two particles *are not* entangled, on what basis could you answer "no"? As a simpler case, is it possible to construct three particles A, AB, and B where AB is entangled with both A and B?
It just bugs me that the typical account of this effect rarely gets past the word spooky before exposition ceases, as if the very phrase "faster than light" causes some kind of cerebral blood flow trauma in any person who has devoted eight years of higher education in grappling with the consequences of E=mc^2.
"...we can't currently control what state the two disentangle into"
This has been the central issue to me since I first started studying quantum mechanics. The other is, why exactly do we need to? Given an entangled pair of photons, measuring ones polarization will tell you what the others polarization is. So, at this point we now know what the polarization of each is. Are the photons still entangled after the first was measured? If so, then the following experiment can be setup...
1. Place an entangled photon generator exactly half way between earth and mars.
2. Do not aim the photon outputs (beams) at earth and mars, but aim the beam at a 90 degree angle to earth and mars.
3. Immediately measure the polarization of one of the photons so that then, both photon polarizations are known.
4. Now, transmit the "known" polarization (as binary data) on another channel, an out of band beam, at the speed of light to both earth and mars.
5. Having sent the "known" polarization of the entangled photons, now reflect (with mirrors) the entangled photons (which have now traveled for some distance from the source) to both earth and mars. One photon reflects to mars, the other the earth.
6. On earth, we first receive the polarization data from the out of band light beam, which mars also receives at the same time.
7. Now since we know what the polarization will be when the entangled photon arrives, we then make an "adjustment" to its polarization.
8. The mars receiver then sees that the polarization of the entangled photon it was supposed to get, isn't actually what is measured.
Why doesn't a scheme like this work?
The other minor thing I don't understand about quantum mechanics is why such a big deal is made about the dual slit experiment. The dual slit experiment is in my opinion not the biggest mystery. The bigger mystery is why does a light beam diffract around "an edge" to begin with. It seems rather "obvious" to me that if a light beam passes a single edge of a razor blade and "diffracts", generating a wavelike pattern on the detector, then having two slits will obviously generate the famous wave pattern in the dual slit experiment. No, the central issue to me in quantum mechanics is why we know so little about photon control in the first place. Ok, so any change in an electrons momentum causes photons to be given off. But this momentum change is constrained so that the photon energy must leave the electron in finite units of Planks constant. This would lead us to the inevitable conclusion that space and time can be quantized, and that we live in a digitizable universe, right? So if I ask for a cup of steaming hot earl grey tea from the replicator, given enough power and control I will get it right?
CUrrently we lack an ability to select an electron based on spin without entangling it with another electron and thus breaking other entanglements. However, is this an issue with our technology or with the science behind it?
Suppose we look at photons with entangled polarities instead. At least in theory we ought to be able to use birefringence to select photons based on known polarity properties. Thus we ought to be able to know what the polarity was supposed to be before we rotate it. Thus the noncommunication theorem might be a mere technological limitaton as opposed to a fundamental principle. We will have to see.
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Before complaining, please know what you are talking about... A quick search on wikipedia would tell you: Einstein received his Nobel Prize for works on Quantum Theory!
http://en.wikipedia.org/wiki/Albert_Einstein: Einstein received the 1921 Nobel Prize in Physics "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect."
http://en.wikipedia.org/wiki/Photoelectric_effect: The photoelectric effect is a quantum electronic phenomenon in which electrons are emitted from matter after the absorption of energy from electromagnetic radiation such as x-rays or visible light. (...) The photoelectric effect helped further wave-particle duality, whereby physical systems (such as photons, in this case) display both wave-like and particle-like properties, a concept that was used in quantum mechanics. Albert Einstein mathematically explained the photoelectric effect and extended the work on quanta that Max Planck developed.
If we put entangled photon pairs down different fiber lines, and include a birefringent component to split the beam into polarized components... Each photon ought to essentially split itself. We wouldn't know which path a given photon took until we measured it, but we would know what the properties were supposed to be based on the waveform collapse.
:-)
In this case, the observation would be the exact same as it the photon actually had a discrete property which caused it to choose one path as it hit the crystal.
Note, however, that Heisenberg never suggested that the photon would be both at once. He simply said one could not *know* what state it would have until observation without knowing the exact "state of everything else in the universe" ("Physics and Philosophy"). Most physicists also don't suggest that an electron takes up the entire space of an electron cloud, just that such is a "useful way to think about it."
In short in this case, we cannot know whether the photon *really* took both paths and later collapsed that into a choice, or chose one in when it reached the crystal. Postulating about unknowables seems to be a little like Intelligent Design. On the other hand, you may just be confusing the map with the territory
IANAP, but there were plenty of them in my family.
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If you measure your atom how do you know it was untangled by the other guy before you measured it, or by you in the act of measurement?
No sig today...
To hell with atoms- fisherman have entangled entire schools of fish for thousands of years...
Haha, you should have put UPS in the "especially" category. I did the Xmas time truck worker thing during winter break from college a few times and if it didn't say "Liquid" on it we had no reservations about treating it like hell.
There is more to science than physics!
www.iomalfunction.blogspot.com
This small side-effect is probably fascinating only to me, but wouldn't a system of communication based on this kind of entanglement mean that the medium for communication would be a limited resource (i.e. when you run out of entangled particles you can no longer communicate with the other party)?
It strikes me as very odd that something used only for communication ("entangled particles") might someday be counted along with things like "food" and "oxygen" as vital, but limited resources for long-distance travel. In fact, it seems like they may eventually be the most vital resource: things like food and oxygen are relatively sustainable in that they can be grown, purified, distilled, extracted, etc. but entangled particles from earth would be impossible to reproduce or replace without direct contact with earth (or at least, direct contact on the order of a very very long fiber optic cable).
Anyway, just a musing.
Don't usually reply to AC's, but no, the speed limit arises not because of something we noticed in "particle accelerator experiments" it is because of the geometry of space time, which is different than the euclidean geometry that we expereince at low speeds and energies.
If you could send something out faster than the speed of light, then you can truly send things into the past and there by violate causality. If you want to know why this is, study Minkowskian geometry, and particularly its Lorentian coordinate changes which correpond to frame changes arrising from changes in speed, something that is very trival in Euclidian geometry, but not in our world.
So either:
1 - you can't go faster than the speed of light.
2 - you can, but we don't have free will, and something else keeps you from violating causality.
3 - It looks like you can, but somekind of multi-world split resolves the paradox
What you are describing is the propagation of a pressure wave in the material. Pressure waves are also called "sound", and travel at the speed of sound which is orders of magnitude slower than the speed of light.
Imagine the wire is a long rod - you hit one end with a hammer, and the other end doesn't make a sound (or move at all) until the sound wave gets there.
My amazing wife - Artist, Author, Philosopher - Laurie M
So that's how the Cortex works!
Is how many people are willing to make definitive statements about physics when it's clear they don't begin to understand relativity. I especially love the explanations about why quantum mechanics is all wrong. Go read a book for God's sake.
Or
4. Our knowledge of the universe is quite limited at this point and we can in fact exceed the speed of light without violating causality.
Furthermore, in time it's quite likely to be found that Special/General Relativity and the mathematics that explicate them including Minkowskian geometry do hold true, but only in a limited context (close to light speed), and have little to no relevance once C has been exceeded.
"Observed" basically means that information about it is present in some other system. So you don't need a human to notice it; a detector completely suffices.
About what observes all the particle around you when you're not looking: The environment does (by simply interacting with them). That's what is called decoherence.
The Tao of math: The numbers you can count are not the real numbers.
You are using 'Send'. Quantum entanglement does not 'send' anything.
When you say 'send' you imply that the effect travels through the space between the two particles. This is not what happens. It never moves through then space between them. That's why it's "spooky at a distance" and not "very fast at a distance".
"If one assumes that the speed of light is the fastest one can send information in the universe"
Using quantum mechanics I know exactly how to use it to send data. For 10 million dollars, I'll be happy to tell someone.
The Kruger Dunning explains most post on
", in order to separate the two you need to transmit some additional information by classical means"
No, you do not need to transport it seperatly, per se. You only need to have the receive understand how to interpret the spins. This can even be done even if the spin direction is completely random.
The Kruger Dunning explains most post on
Good luck with "carefully" during the rocket take-off and all those G-forces.
I am anarch of all I survey.
It is one of the great ironies of history that Einstein, who laid the foundation for quantum mechanics so well with this paper (as well as working out the Bose-Einstein statistics), never accepted quantum mechanics, and he always believed that quantum mechanics appeared so weird only because of our lack of understanding of nature (i.e., there must be some other variables hidden from us that, when worked into a proper equation, will describe nature)
.. or 4. You cannot 'exceed' speed of light but can communicate 'instantanly' with a particule far away, because, in fact, it is not travelling at all.
.. there just a problem because it is a 'computer' in the example. Sooo ... maybe it is your multi-world explanation you were talking about .. I didn't really understand what you meant, sorry ... or something else, but, just saying that, logically (sort of) you don't need to exceed speed of light to transmit information faster than speed of light (in the example, speed would be limited by the speed of execution of the computer running the simulation) ... just that the explanation for it to be possible is not logical (in our current knowledges)
Look just imagine the world as a computer modeling a world with physic law (our world simulated in a computer). Now there is a law called 'relativity' (simulated) that limit the movement of physical object; but, the 'computer' could know instantaly that a particule changed stated and adjust the other one without needing to 'tavel' the information at the speed of light.
No causality or law would be violated
It seems that our inability to understand Quantum Mechanics (spooky) represents an inability to collapse our wavefunction, as Schrodinger posited.
I think that'll be the Quantum Internet's slogan.
What wouldn't Jesus do?!
Imagine two entangled photons travelling away from each other after a radioactive decay, each moving at the speed of light and each with opposite polarizations: lets say one up and one down for one particular instance.
Now each strikes a polaroid filter both aligned at +45 degrees i.e. both have same orientation. This means that each photon has a 50% chance of passing through the filter. However in the entangled case exactly one photon will pass the filters EVERY time.
Since SR tells us that there can be no information transmitted between the two after the decay we can imagine doing the same thing with two computers. At the start they can transmit any info they like between themselves, then they are disconnected and each, separately told the angle of the polaroid filter. Now each has to decide indpendently whether or not their photon should pass the filter and every time they do exactly one should always say "pass".
You can come up with a good approximation to what actually happens in rel life but it is impossible to come up with exactl one photon passing everytime. The only way that you can do that is to allow some communication between the two photons...which SR tells us is not possible. While the overall effect does not violate SR the problem is in understanding how the two photons decide which is going to pass without invoking FTL communication.
The point is that one can not even define what it would mean to exceed the speed of light. The notion is distance is very different in a Minkowskian geometry. Going "faster" than the speed of light means you have a "timelike" trajectory, which is essentially (when looked at from the appropriate reference frame) equivalent to traveling backwards in time.
If you can transmit information faster than the speed of light, then you can signal into the past. And then you have to deal with all the causality paradoxes.
The problem I see with the Quantum No communication theorem is that it accept that there is an interaction than could 'travel' FTL but since no information can be transfered that way, then causality is not affected.
I don't know but I really see that reasoning looking like if there was an astral agent that would be looking at our world and accept that some 'things' (whatever affecting the state of the entangled photon) can go FTL but, OMG if some of it would be actual information that could lead to human (or anything else) violating causality then and only then it is not permitted. Sorry but that seem pretty absurd to me. And, isn't the entangled particle state changing information in a way, even if WE cannot know. Please explain this to me.
This is why I put up my theory than the information, who would NOT be travelling (physically) FTL, hence NOT affected by relativity and then NOT going backward in time seem more 'logical' to me (I didn't say plausible since this is just a random idea that popped in my head but well, going backward in time just seem crazy). You can check my more recent post somewhere in this thread, where I tryed to explain in a better way what I meant.
I'm using whichever service charges by weight.
Sirs,
My theory entanglement of atoms over fiber eventually without fibers was for the first time
verified. UM concept and my own published many years ago applies directly to my patents.
http://colossalstorage.net/home_entangled.htm
We are in secret test bed proof on many of my nanotechnology concepts.
Regards,
Michael
1) This all assumes that the accepted Minkowskian geometry is the exactly correct representation of time-space. While it seems a good fit now, so did Newtonian geometry until recently.
2) Exceeding the speed of light is easy. What is hard or impossible is observing something else exceeding the speed of light. If you define exceeding the speed of light as going to a place at a distance of d, in less time than d/c, then exceeding the speed of light is done at any "observed speed" greater than about 0.88 c. This reflects the fact that it is not an issue of a limitation of speed, but a reality that speed through space and "speed" through time are inherently linked. The limitations are not in how fast we can get somewhere, but that getting somewhere extremely fast will pull us through time fast as well, meaning that the people left behind will not live to see us reach the destination.