Speedy Entangled Photons:
August 24, 2008 5:00 PM   Subscribe

Whether Einstein's "spooky science" or quantum weirdness, the Geneva tests that show entangled photons traveling at 10,000 times the speed of light are stirring up challenges and "Alice in Wonderland" discussions about "subatomic particles communicating nearly instantaneously at a distance."

... and much discussion and rejection ("Bohm's Bummed"!) of the experiments ensues ... along with speculation that these tests are proof of metaphysical theories or even teleportation .



Could it be love? ....
"Entangled photons are a peculiar consequence of quantum mechanics. Tricky to generate, they remain interconnected even when separated by large distances. Merely observing one instantaneously affects the properties of the other."
posted by Surfurrus (73 comments total) 24 users marked this as a favorite
 
Claims that quantum mechanics means that magic is real in five, four, three, two...
posted by Pope Guilty at 5:05 PM on August 24, 2008


Science is so cool.
posted by synaesthetichaze at 5:06 PM on August 24, 2008 [1 favorite]


Here is an interesting explanation on why entanglement cannot be a vector for information. Unfortunately I kind of have to take this guy's word for it, since I have no idea about these things.
posted by synaesthetichaze at 5:12 PM on August 24, 2008


General relativity states that information cannot travel faster than light. Quantum entanglement does not violate that principle (much as I'd like it to), as I understand it, because the indeterminacy principle of quantum physics states that even after the properties of the first photon are observed and the wave function collapses, details about it are probabilistic. No 'information' is 'transmitted' to the quantum-entangled partner.

Or am I mistaken?

Also, doesn't the idea of a 'frame' sound an awful lot like the aether that Michaelson and Morley failed to detect?
posted by stavrosthewonderchicken at 5:13 PM on August 24, 2008


The article said that the minimum speed of entangled photon interaction is 10,000 times the speed of light
posted by Paris Hilton at 5:13 PM on August 24, 2008


¯\(0_o)/¯
posted by turgid dahlia at 5:19 PM on August 24, 2008 [8 favorites]


can we edit this post?
photons can only travel at the speed of light.
posted by bhnyc at 5:21 PM on August 24, 2008


Nothing's moving at 10,000 x light speed -- no photons (entangled or otherwise), no information.

The experiment says that if there were some sort of "communication" between the photons (like a pilot wave or some such), it would have to travel many times faster than light speed for everything to work properly. (And it can't carry information if it does move faster than light.)

Gisin's group in Geneva has been putting limits on "spooky action" like this for years. (In fact, last I remember, the limit was more than 1 million times faster than light speed -- have to reread the old paper to see what the difference is.)

More on this in Decoding the Universe.
posted by cgs06 at 5:22 PM on August 24, 2008


Claims that quantum mechanics means that magic is real in five, four, three, two...

One! Quantum mechanics means that magic is real!

*teleports back to the Outer World*
posted by Marisa Stole the Precious Thing at 5:24 PM on August 24, 2008 [5 favorites]


God, you guys are so educated stupid.
posted by Saxon Kane at 5:31 PM on August 24, 2008 [3 favorites]


I realize the story (fourth link) is by a science reporter interpreting stuff published in scientific journals, but I have to be skeptical about anything that describes photons as "sensing," "knowing," and "sharing" information.
posted by beagle at 5:34 PM on August 24, 2008 [2 favorites]


The experiment says that if there were some sort of "communication" between the photons (like a pilot wave or some such), it would have to travel many times faster than light speed for everything to work properly. (And it can't carry information if it does move faster than light.)

Yes, but that puts you in a rather delicate position.

Take two entangled photons. Separate them by some great distance. Observe one of them - if it's in state A, you know that the other one is in state B. This experiment has been done many times.

So how does that happen?

Are they communicating with each other instantaneously? Apparently not.

Well, is there a "hidden variable"? In other words, even though the two photons "look" identical, is the result of the experiment determined in advance so one "knows" to become A, the other one "knows" to become B?

Well, that's unfortunately even worse. This lovely result shows that this is apparently incompatible with human free will, oh yes. And a series of other negative proofs have shown for example that if you have hidden variables, they have to have all sorts of unearthly powers.

I just found a really nice discussion of this.

So it seems that there are no hidden variables AND there's no spooky action at a distance, so the only interpretation appears to be "that's what our equations tell us" or "it just happens that way" (the Copenhagen interpretation) - which is in essence no explanation at all.
posted by lupus_yonderboy at 6:10 PM on August 24, 2008 [5 favorites]


This lovely result shows that this is apparently incompatible with human free will, oh yes.

I'm going to read that "nice discussion" you posted, but I have to say that this is not a problem of explanation, but a problem of acceptance.
posted by adamdschneider at 6:41 PM on August 24, 2008 [2 favorites]


I look forward to reading these links when I am not drubk.

Not that they'll make any more sense to me.
posted by BitterOldPunk at 7:20 PM on August 24, 2008 [2 favorites]


I wonder if we'll ever work this stuff out.
posted by nudar at 7:20 PM on August 24, 2008


I'm going to read that "nice discussion" you posted, but I have to say that this is not a problem of explanation, but a problem of acceptance.

It's still a dreadful explanation for everything: "It was all predestined to happen this way but there's no other reason."

And the paper seems to show that we wouldn't even have the appearance of free will we certainly do have now.
posted by lupus_yonderboy at 7:36 PM on August 24, 2008


The problem isn't "Working it out" the problem is explaining it with some pithy metaphor so that people who don't get it can scratch their chins and think they get it (see the third law of thermodynamics, for example)
posted by delmoi at 7:37 PM on August 24, 2008


The biggest obstacle to producing any sort of information-carrying device using these theories is, of course, the management of the entangled photons. Even to perform these experiments, the scientists had to use teeny-tiny tweezers to disentangle the photons and put them in separate boxes before carrying them to distant locations where they could measure the effect. Compounding all this, of course, is the need to perform everything in the dark.

Some steps are being made to alleviate the last restriction. With the invention of the world's smallest Sharpie, scientists have found that they can write on the photons, giving them names for later identification. Once a pair of entangled photons has been created and marked, they can be stored in Mason jars for later retrieval. There is even talk of a sort of bus service where jars full of once-entangled photons can be delivered to any stop along the lab circuit where the scientists can pull out the particular photon they're looking for and then send the rest on their way.

Some problems were encountered with this system, the largest being the tendency of the lonely photons to re-entangle themselves with newly disentangled photons in the jars. This caused the ex-partners of the newly entangled photons to cease all communications together. Some progress was made when the photons were segregated into blue jars and pink jars according to the spin of their quarks, but the whole system fell apart when homophotonism was discovered in some of the jars by the Swiss Calvinists.
posted by joaquim at 7:47 PM on August 24, 2008 [12 favorites]


It seems that Rudy Rucker is the only mathematician who dares to tackle this kind of question:
There will be an amazing new discovery in physics on a par with the discovery of radio waves or the discovery of nuclear reactions. This new discovery will involve a fuller understanding of the level of reality that lies "below" the haze of quantum mechanics—suppose we call this new level the domain of the subdimensions.

Endless free energy will flow from the subdimensions. And, by using subdimensional shortcuts akin to what is now called quantum entanglement, we'll become able to send information over great distances with no energy cost. In effect the whole world can become linked like a wireless network, simply by tapping into the subdimensional channel.
Read the whole (fun) story in Edge's "What are you optimistic about?" (scroll down to Rucker's text).
posted by bru at 8:12 PM on August 24, 2008 [3 favorites]


There will be an amazing new discovery in physics on a par with the discovery of radio waves or the discovery of nuclear reactions.

It seems far more likely that the new discovery will be that noise (aka randomness) is "real". We just have to live with certain fundamental limits, just as with thermodynamics.
posted by Chuckles at 8:28 PM on August 24, 2008


It seems far more likely that the new discovery will be that noise (aka randomness) is "real". We just have to live with certain fundamental limits, just as with thermodynamics.

We already know this is true, though. The issue is actually not randomness - it's that the results of reading the entangled particles are completely correlated no matter how far apart they are.

If everything were just random, when you read the entangled pair separately, you'd get AA, AB, BA or BB with equal probabilities. That'd be completely consistent. But that's not what happens - you only ever get AB or BA.

Somehow even though these two variables look random, they're in fact completely correlated.
posted by lupus_yonderboy at 8:53 PM on August 24, 2008


Does Rudy have a new scifi book coming out soon?
posted by Blazecock Pileon at 8:55 PM on August 24, 2008


I'm just happy there's a branch of science where "weird," "strange," and "spooky" are all perfectly acceptable descriptors.
posted by lekvar at 9:05 PM on August 24, 2008 [2 favorites]


it's that the results of reading the entangled particles are completely correlated no matter how far apart they are.

Well, the way I read some of the content is that certain people are hoping for magical speed of light violating new physics, which this is not.

We already know this is true, though.

Well, I'm not a physicist, but based on certain talks I've heard, and articles I've read, I think there is a lot of debate about the truth of randomness. For example, I get the impression that the whole "wave function collapse" language exists purely to avoid accepting it.
(well, I guess more a way to avoid accepting the combination of duality and randomness - the need to reject either seems simply dogmatic to me, given my background in information theory - I don't know though, I feel like I'm forgetting some math :P)
posted by Chuckles at 9:06 PM on August 24, 2008


So it seems that there are no hidden variables AND there's no spooky action at a distance, so the only interpretation appears to be "that's what our equations tell us" or "it just happens that way" (the Copenhagen interpretation) - which is in essence no explanation at all.

Strings, maybe? I can't seem to find a definitve verdict on Higgs Boson at the moment, though. I'm seeing articles from 2004 saying "may have been found", but another from last June saying "hasn't been observed". There's a proposed test of string theory in 2006, another from earlier this year, and the impending end of the world on September 10. But is the jury still out on this?
posted by Marisa Stole the Precious Thing at 9:17 PM on August 24, 2008


If this was important or true, I am sure it would have been covered in the Bible.
posted by Mr_Zero at 9:40 PM on August 24, 2008 [1 favorite]


I'm just happy there's a branch of science where "weird," "strange," and "spooky" are all perfectly acceptable descriptors.
posted by lekvar


Charmed, I am sure.
posted by pointilist at 9:59 PM on August 24, 2008 [7 favorites]


Light cone diagrams are helpful for me to accept this stuff.Everything inside the cone exists at light speed or below, is local. The spooky stuff is outside the cone, non local, this is where information gets around simultaneously. or at least that's what I got from Robert Anton Wilson's explanation- Illuminati Papers
posted by hortense at 10:10 PM on August 24, 2008


Magic is real, because what the bleep do we know?
posted by benzenedream at 10:48 PM on August 24, 2008


For example, I get the impression that the whole "wave function collapse" language exists purely to avoid accepting [randomness]

Not at all - you can actually detect the fact that the collapse has occurred, there's a real event happening. It's possible to detect that a system is in a "Heisenberg state" without actually observing the contents of the system (and collapsing the uncertainty).

In fact, if the system were in fact "random" in the naive way of thinking of it then the wave function would be an excellent way to model it - just a probability distribution(*) that says where the particle is likely to "be".

When the randomness "goes off", one specific result is chosen and all other ones disappear. Before you throw a die, it could be one of six possibilities; once it's landed, there is only one possibility, your probability function has collapsed.

The issue isn't that, it's the entangledness, that you can stretch this uncertain state across the universe.

(* - to be exact, the probability is the square of the wave function)
posted by lupus_yonderboy at 10:57 PM on August 24, 2008 [1 favorite]


The issue isn't that, it's the entangledness, that you can stretch this uncertain state across the universe.

The randomness angle is important for understanding why entanglement doesn't violate the speed of light, but I was never suggesting that entanglement ideas effect the randomness question.

Anyway, reading wiki about wave function collapse, it seems to be about avoiding duality, rather than randomness.
(more discussion on the existence of duality)

I've had debates with laymen who staunchly believe that randomness can't be 'real', but perhaps I'm misremembering encountering any half way authoritative expression of that opinion.
posted by Chuckles at 11:38 PM on August 24, 2008


ARGH! The wiki talk page on duality is a nightmare! Perhaps it would be more accurate to say wave function collapse is a way for physicists of varying opinion to avoid provoking the duality debate..

Anyway, this is way off topic now :P
posted by Chuckles at 11:57 PM on August 24, 2008


You know, something that keeps bothering me about quantum waveforms and collapses, is that it looks an awful lot like a "lazy-evaluation" algorithm running on a computer.

That is, it looks like a great deal of reality doesn't exist until something looks at it very closely; it's as though it's not being figured out unless and until it's needed. Barring someone snooping with a super-sensitive probe of some kind, perhaps it's possible to just abstract large swaths of quantum reality and model them as larger, discrete chunks. This would be a great way to save on "computer" power. (though I imagine any device actually running our universe would be so unimaginably strange that calling it a 'computer' would be the grossest of abstractions.)

Things like quantum entanglement could easily just be side effects of the algorithm that's running. When something has to be figured out, if there are two entangled particles... well, if it's actually a simulation, they're going to happen at the exact same time. In relativity, the 'exact same time' is a meaningless idea, but that wouldn't necessarily be true in a larger reality that's running ours as a model.

I guess it's just the more I think about it, the more I realize that we really could just be a model. I guess it's a new flavor of 'brain vats on Jupiter', but that lazy-evaluation stuff makes me say, "hmmm". And, of course, there's the argument that sufficiently advanced humans would be likely to run 'ancestor simulations', so if we grant that humans are capable of developing to that complexity, the chance of us being the FIRST humans to do so is vanishingly small. That also explains the Big Bang; time zero would really be time zero. It would be very difficult (impossible?) to determine anything about whatever greater reality is running ours.

Whatever's really going on, all this quantum weirdness is a great puzzle. It's a sign that we most emphatically don't know everything yet, and that things aren't as certain as we'd like to believe. The rules of the universe, as we know them now, are annoyingly tedious and boring, so finding ways around some of them would be great stuff. :)
posted by Malor at 1:42 AM on August 25, 2008 [9 favorites]


Oh, another point I forgot: there appears to be a 'shortest measurable time', the Planck Time. That might be the tick rate of the simulator.
posted by Malor at 1:44 AM on August 25, 2008 [2 favorites]


I like the Coen brothers' explanation.

"This 'Heiny', he even wrote it out in numbers."
After that, it's all Greek.
posted by From Bklyn at 2:45 AM on August 25, 2008


Easier to describe with diagrams, but I always liked the interpretation using the transactional interpretation / Wheeler-Feynman absorber theory where you're describing a collective property of the one system. You appear to get your spooky action at a distance from the single distributed event when advanced and retarded waves cancel out everywhere except (because you've built your perfect entangled symmetry) at the pair of events. Hope it hasn't been killed by a clever experiment somewhere.
posted by snarfodox at 3:00 AM on August 25, 2008


Malor: That is, it looks like a great deal of reality doesn't exist until something looks at it very closely; it's as though it's not being figured out unless and until it's needed.

Yes. Wheeler's delayed choice experiment:

We have chosen whether to know which side of the galaxy the photon passed by (by choosing whether to use the two-telescope set up or not, which are the instruments that would give us the information about which side of the galaxy the photon passed). We have delayed this choice until a time long after the particles "have passed by one side of the galaxy, or the other side of the galaxy, or both sides of the galaxy," so to speak. Yet, it seems paradoxically that our later choice of whether to obtain this information determines which side of the galaxy the light passed, so to speak, billions of years ago.

In short, the past is constructed/created so as to be consistent with our observations today.
posted by vacapinta at 3:23 AM on August 25, 2008 [1 favorite]


snarfodox, I'm also a fan of the transactional interpretation. The two particles are communicating. But they're doing so by sending signals that travel backwards in time. The problem is that the theory is too neat. These signals travel backwards in time with the particle itself, then reverse time-direction to follow the other particle. And the whole thing looks...like what we see as an experiment. I dont think its been disproven because, as it stands, its more of a philosophical interpretation.
posted by vacapinta at 3:47 AM on August 25, 2008


Malor, the lazy evaluation bugs me to no end. But its not the only one.

The fact that at the core of thermodynamics is entropy, a measure of randomness. That is a great one. Just like in data compression, and hence storage. Hell, if you can throw in a little optimization, like a rule that says the entropy of a system only increases, you could be looking at constant storage requirements even in an expanding universe!

And then of course if you have a really really big number of particles in a very small space, you could just slow down time locally to keep up on the simulating side.

Bugs me to no end.
posted by CautionToTheWind at 4:40 AM on August 25, 2008 [2 favorites]


I'll never understand why it isn't obvious that what we have here is multiple universes. There is no communication between particles. It is just that there are two universes. In Universe A, both particles are in one state and in Universe B they are in another. Observing one particle in the first state means we are in Universe A. The other particle in this universe is in the same state. No communication is required.

This isn't complicated or magical. It happens in any situation where two objects have related properties. For instance, I have two kids that need lunches made to bring to school. If I remember to make their lunches, they both have them. If I forgot, they both have to buy their lunch. My two kids attend school in different buildings across town. If I a teacher observes one child eating from a lunch box, the other one will be eating from a lunch box too. Was an instantaneous phone call placed to make this happen? Obviously not.
posted by DU at 4:43 AM on August 25, 2008


I simultaneously read and didn't read TFA.
posted by kcds at 4:45 AM on August 25, 2008 [1 favorite]


I'll never understand why it isn't obvious that what we have here is multiple universes. There is no communication between particles. It is just that there are two universes. In Universe A, both particles are in one state and in Universe B they are in another. Observing one particle in the first state means we are in Universe A. The other particle in this universe is in the same state. No communication is required.

Because thats a hidden variable theory. In this case, the "agreement" between the particles beforehand as to what Universe they're in. Bell showed why hidden-variable theories dont work.
posted by vacapinta at 5:16 AM on August 25, 2008 [2 favorites]


It's not that magic is real, but that reality is magic.

That is, it looks like a great deal of reality doesn't exist until something looks at it very closely

Anthropologists! Anthropologists!
posted by pracowity at 5:17 AM on August 25, 2008


some more quantum weirdness :P
posted by kliuless at 5:20 AM on August 25, 2008


Isn't the whole direction of physics to wipe out free will? We're looking for laws that make things predictable: if you set up all the particles, energy, vectors, space, etc. ahead of time and let them loose, you show know exactly what will happen if you know the ruleset they move by. The Universe is the sum total of all the particles, energy, etc., obeying all the rules. Seems pretty predetermined to me.
posted by rikschell at 5:24 AM on August 25, 2008


Because thats a hidden variable theory...

I'm not an expert, but I don't see how this is applicable. I'm not saying there is an "agreement" between the particles beforehand as to what Universe they're in. They just are in a universe. They don't have to know anything.

It's exactly like the lunches example. The kids themselves don't have to know they are in the same universe. The correlation of their lunches is due to the logic of how I give them the lunches. If I give one to A, B necessarily has one. Therefore when I check one, I know both.
posted by DU at 5:32 AM on August 25, 2008


It's exactly like the lunches example. The kids themselves don't have to know they are in the same universe. The correlation of their lunches is due to the logic of how I give them the lunches. If I give one to A, B necessarily has one. Therefore when I check one, I know both.
posted by DU at 1:32 PM on August 25 [+] [!


Except that the lunches example has nothing to do with the experiment. Its only a good analogy if you only read news articles. Seriously, there's a lot of good info on Wikipedia. Go read up on this if you're interested.

A better example would be: Either neither or both kids get sandwiches. Also, neither or both kids get milk.

So, you check to see if kid A has a sandwich. 50% of the time, he does. It then turns out that whenever you check if kid B has milk, he does have milk about 50% of the time. Ok, fine.

Now, you note that whenever you check if kid A has milk first, it turns out kid B has a sandwich about 70% of the time.

Huh wait? Your first check (assuming all or none get sandwiches) is that they have sandwiches half the time. But your second check shows that if you check for milk, kid B has a sandwich 70% of the time. And this happens repeatedly, after many experiments.

There is no way you can pack lunches to arrange this. Because all it depends on is what we decide to check on later in the day. So, whats going on? The kids are communicating somehow? Right?
posted by vacapinta at 6:05 AM on August 25, 2008 [2 favorites]


...if you check for milk, kid B has a sandwich 70% of the time. ... There is no way you can pack lunches to arrange this.

Out of every 100 lunches I pack (or rather, pairs of lunches since I make them the same for both kids), I make:

40 with sandwiches and milk
10 with sandwiches and no milk
10 with no sandwiches but with milk
40 with nothing

The chance of finding a milk in a given (pair of) lunches: 50%
The chance of finding a sandwich in a given (pair of) lunches: 50%.
The chance of finding a sandwich in a (pair of) lunches that I've already found a milk in: 80%.

Amount of communication between kids: 0
posted by DU at 6:29 AM on August 25, 2008


The chance of finding a sandwich in a (pair of) lunches that I've already found a milk in: 80%.

No, that wasnt my example. The chance of finding a sandwich goes up to 70% just by checking for a milk. Whether you found a milk or not doesnt matter.

The point is we're not talking about macroscopic reality but about quantum reality where we have state functions which are superpositions of different variables.
posted by vacapinta at 6:44 AM on August 25, 2008


What a naughty non–law-abiding universe we live in.
*hugs universe, tousles universe's hair*
posted by Mister_A at 6:52 AM on August 25, 2008


OIC. Yes, that invalidates my lunch example but only, it seems to me, for relatively superficial reasons. The issue here isn't that variables are entangled within an particle but that particles are entangled long distance.

If you leave it at "these distantly separated particles carry one bit of information, so when you know one you know the other" there is no comm problem.
posted by DU at 6:58 AM on August 25, 2008


And then of course if you have a really really big number of particles in a very small space, you could just slow down time locally to keep up on the simulating side.

Well, remember, if we are a simulation, we don't know what speed we're running at. Our minimum possible time period appears to be the Planck Time unit, but there's no way to know how long that takes to simulate. It could be one PT, or it could be the equivalent hundred million years, and there's no way we could ever tell.

Of course, a containing universe is likely to be more complex than ours, so even the concept of time may not really apply. But, as a hunch, I think time might exist in both, because lazy evaluation would be used to reduce computing requirements. And, if you don't have time, you don't really have limits on computation.

Your comment re:entropy is a very interesting one... the Universe can never contain more information than when it started. The total amount of energy, and thus the total amount of information, is constant. Between that and having any amount of time it needs per 'tick', the simulating computer wouldn't need upgrades for the duration of the entire run. The thought occurs that if we do too much of this measuring stuff, and we're not what they're really interested in simulating, they could delete us as an annoying consumer of resources. :)

The Universe is the sum total of all the particles, energy, etc., obeying all the rules. Seems pretty predetermined to me.

That's the thing, rikshell; the more we dig, the less that looks to be the case. Quantum mechanics appears to be the most purely random mechanism we know of. And, because of things like vacapinta's link up there, it looks like the Universe is rearranging itself in the past to suit our present observations. Not only are outcomes not predictable, but what happened a billion years ago changes to match our observations today. We can see that on a small scale now, if you dig into those links up there. On our scales, it's just a few nanoseconds earlier, but we can still see what appears to be retroactive changes in what happened in the past to make measurements in the now consistent.

That really sounds like a simulation to me. It'd have to be created by a godlike intelligence or intelligences, but to simulate something of X complexity, you need a device of even greater complexity. So that's pretty much a guaranteed for any simulation scenario.

Oh, and DU: what vaca's saying is that the actual act of looking for a milk increases the odds of then finding a sandwich. If you just look for sandwiches, you find one 50% of the time, but if you look for milk first, whether or not you find any, the odds of finding a sandwich increase to 70%.
posted by Malor at 6:58 AM on August 25, 2008 [1 favorite]


Sigh, first paragraph, "equivalent hundred" should be "equivalent of a hundred".

Also, I'm not sure I was clear enough that a probabiilstic universe appears impossible: if things change in the past to match present observations, that means that they weren't fixed in the first place, just approximated. There's room for lots of randomness in that situation.
posted by Malor at 7:02 AM on August 25, 2008


Ok, so this is from vacapinta's link is melting my mind, A Delayed Choice Quantum Eraser. In the lunch box scenario, it's like the first kid's lunch gets checked for apples at 11:30, then the second kids lunch gets checked for milk at 12:00. If the second teacher checks for milk the probability the first kid had apples is 50%, if the second teacher doesn't check the probability is 70%. So the if the second teacher checks or not can change the probability distribution of something that has already happened.
posted by afu at 7:38 AM on August 25, 2008


To try to summarize that second experiment, it looks like this is what happens:

1. They emit a signal that causes two entangled photons to be generated, from one of two possible source locations.
2. One photon goes to a detector early.
3. The second photon follows one of four possible paths. In two of them, things are arranged so that it's not possible to determine which source generated the pair; they actually remove data from the photon by deliberately confusing the path it followed. Down the other two, the 'which-path' information is preserved.
4. The measurements at 2, which are taken several nanoseconds before the measurements at 3, will reflect either wave or particle results, depending on whether the entangled photon was 'erased' or not.

In other words, if the entangled photon was 'erased' LATER THAN THE DETECTION, the first detector detects a wavelike photon. If the entangled photon wasn't erased, the detector detects a particle photon. The measurement at time T is affected by an entangled erasure AT A LATER TIME.

That's not just spooky action at a distance, that's fucking spooky action at a distance.

As afu says, that's like checking for milk at noon affecting whether or not the other kid had a sandwich at eleven.

It's actually a bit frightening.
posted by Malor at 8:53 AM on August 25, 2008 [3 favorites]


I haven't yet figured out how many cups of coffee should pass through the slit before I can understand this.
posted by seanmpuckett at 8:56 AM on August 25, 2008 [1 favorite]


This made me think of the instant communication tools depicted in Ender's Game by Orson Scott Card, which use a fictional subatomic particle (the philote) as means of communicating at faster-than-light speeds. Poking around I discovered that he's not the first to use the Ansible as a term for faster-than-light communication - that honor falls to Ursula K. Le Guin. I've also discovered the word Superluminal, which makes me irrationally happy, and I am walking around the apartment saying it out loud.
posted by kahboom at 8:59 AM on August 25, 2008


I'm not an expert, but I don't see how this is applicable. I'm not saying there is an "agreement" between the particles beforehand as to what Universe they're in. They just are in a universe. They don't have to know anything.

You're using the word "universe" as a substitute for the "hidden variable" - the two ideas are identical.

Q: why did the particle get spin +1?
A1: a hidden variable contained that information
A2: the universe contained that information.

The parallel universe theory doesn't explain any of the entanglement phenomena - it doesn't explain why you never see universes with AA or BB (see my chat above).

You're simply renaming the information in "hidden variables" and making them non-local (but it turns out that if hidden variables existed, they'd have to be non-local anyway...)
posted by lupus_yonderboy at 9:00 AM on August 25, 2008 [1 favorite]


seanmpuckett: all of it, probably. I don't think anyone actually understands this. We can describe it, but we're pretty baffled.
posted by Malor at 9:05 AM on August 25, 2008


"Once a pair of entangled photons has been created and marked, they can be stored in Mason jars for later retrieval."

I think you mean Meson jars.
posted by Eideteker at 9:17 AM on August 25, 2008 [3 favorites]


"In all the equations that describe motion and heat, in all the Feynman diagrams, what's the one variable that you can turn into negative and still get rational answers from?"
posted by spiderwire at 9:20 AM on August 25, 2008 [1 favorite]


So what happens if you have two observers, one relativistically-accelerated, one not, two entangled photons, and the non-accelerated observer collapses the waveform? The accelerated observer sees the collapse before it could have happened in their frame, right?
posted by spiderwire at 9:24 AM on August 25, 2008


"Isn't the whole direction of physics to wipe out free will? [...] Seems pretty predetermined to me."

I think you could more correctly state that the/a goal of physics is to figure out to what extent things are determined.

It's interesting to read physicists basically saying: "Well, Newton wasn't entirely right, so something else came along. QM is likely going to give way to something else at some point." It's like there's a tacit assumption that there is no final answer, no GUT. Instead, scientific knowledge is a continually branching fractal tree, ever reducing but never ending (reminds me of GEB). So we'll probably never get to the point of rigid determinism within scientific laws. And, like in GEB, the system is continually exploring the limits of the system, not just the laws of the system. If no formal system can contain all axioms, it won't surprise me if physics cannot contain all physical laws. It's still interesting to see how far we can get.
posted by Eideteker at 9:42 AM on August 25, 2008 [3 favorites]


I don't know kliuless.. Those links have some problems.

The University of Rochester one say:
Why the objects we see around us every day—in what physicists call the "classical" world—don't behave this way despite being made of these very same strange quantum particles is a deep question in modern physics.
This shouldn't be a mystery to anyone.. The macro scale objects behave like the average of many billions of billions of probability distributions. That the average of a bunch of random experiments turns out to be as fixed and reliable as concrete is no surprise to casino operators..

And the IEEE article isn't better.. "Two Times Zero Doesn't Always Equal Zero" - the expectation that it should is pretty much purely theoretical. Zero is a terribly hard thing to measure.
The new theoretical research examines transmissions of individual quantum states, such as sending a single photon down a fiber-optic cable and reading off its polarization on the far end.
Is it so easy to just casually send a single photon down a fiber optic? I mean, they talk about it as if it is as easy as turning on the oscilloscope. Oh, my mistake, new theoretical research..
Rather than shipping the lone photon down a clean and undisturbed line, the researchers considered sending information down two lines that contained too much static to transmit anything reliably. When the lines were examined alone, each noisy channel proved as useless as a dead telephone jack. However, the researchers calculated that someone on the far end of two noisy channels used together could in fact extract actual information from the individually worthless lines.
First of all, none of that sounds like zero to me. Second, it might be new in the quantum world, but in traditional information theory it doesn't come as a surprise at all that you can use more information to reduce the effect of noise - to average it out, as it were.
“These capacity [calculations] are very nice,” he said. “But from a practical point of view, the motivation is to try to actually build something.”
I'm glad he said that.

So anyway, I'm sure my criticism comes down to bad science writing.. But then, with good writing I bet these things end up sounding like pretty mundane little tiny steps in the development of the theory.
posted by Chuckles at 10:15 AM on August 25, 2008 [1 favorite]


Alright, maybe my previous post on this was a little muddled, so to be more succint: Would string theory, if proven (or at least, in the case of Higgs Boson being found, knowing that it can't be disproved yet), help account for this "communication" between entangled particles?
posted by Marisa Stole the Precious Thing at 10:34 AM on August 25, 2008


Edit from the OP: yes, I should have put "communicating" instead of "traveling" in the original post. Thanks for catching that.

Also, this whole idea has exploded my mind and I, truthfully, did not understand half of what I posted. I have to say this conversation here has only exacerbated my confusion. But, I suspect that is a break through. Mahalo, mahalo! Great links ... they should keep me busy for a while. (Oh, and I really love the story of the mason jars.)

I still think it is about love.
“The most striking thing about this phenomenon is you take two useless things and they become useful,”

posted by Surfurrus at 10:47 AM on August 25, 2008


Malor: Well, remember, if we are a simulation, we don't know what speed we're running at. Our minimum possible time period appears to be the Planck Time unit, but there's no way to know how long that takes to simulate. It could be one PT, or it could be the equivalent hundred million years, and there's no way we could ever tell.

Regardless, slowing down our time in the busy areas would allow the simulation the luxury of statically assigned resources (for example, a fixed amount of godcpu per slice of our space) and still keep sync.
posted by CautionToTheWind at 12:49 PM on August 25, 2008


Would string theory, if proven (or at least, in the case of Higgs Boson being found, knowing that it can't be disproved yet), help account for this "communication" between entangled particles?

I'm already past my knowledge area but I think the answer is "no". The string theory should explain why the particles are the way they are, and why they react the way they do; I don't think it explains entanglement.
posted by lupus_yonderboy at 1:32 PM on August 25, 2008


(I should add I'm sort of out of my knowledge area entirely here. It could be that everything I say is wrong, I'm a mathematician-turned-engineer who's read a lot about this, not really a physicist at all...)
posted by lupus_yonderboy at 1:36 PM on August 25, 2008


Okay, serious question now. Say you got your quantum eraser experiment thingy. In that experiment the sample photon from D0 gets sent to the comparator before the entangled photon, so i guess an electronic description of that photon is in the comparator's wires before the entangled photon from D1-D4 is even considered.

So, does it matter whether or not it's wires that are used? Could the sample photon's state be encoded on punched tape by the detector, which is then streamed to the comparator before the entangled photon is considered?

Could the sample photon's state be recorded by a dude who is looking at a couple of lights (in an enclosed room), filling in a bubble on a scan-o-tron form who then feeds it into a scanner that reads the data for the comparator -- all of this completely unobserved by the primary experimenters? Would that dude's memory get altered after the fact?

How about you publish the god damn thing in a newspaper in Algeria using one or another classified ad, which is then read by a guy in Milwaukee who flips a switch according to 0 or 1 to which ad was placed, which then feeds the data to the comparator so that the experiment can complete?

Huh? Huh? Can it? (puts hanky on head, lows "my brayne hurtz")
posted by seanmpuckett at 2:25 PM on August 25, 2008


In a recent Asimov's Sci Fi, there was an interesting story based around the idea that a bored/depressed scientist decides to redo the Fenymann double-slit experiments and inadvertently discovers that that not only is the ability to observationally collapse the probability wave an exclusively human capability, in that story-universe, not all humans' observations cause the collapse. I asked my friend, a former nuke-physics prof, to read the short story, so he could explain to me which parts of the story were real, and which were fictional.

I would have something more substantial to add to the discussion if he'd gotten back to me yet; instead I will recommend finding the story and giving it a read.
posted by nomisxid at 4:36 PM on August 25, 2008


sean, as far as I understand, no. As soon as anything observes the photon closely enough for it to matter, the state collapses, and it's done forever. It's only when it doesn't matter that it's indeterminate. It's probably the case that nearly all photons come into existence and dissipate without ever collapsing. Hardly anything looks closely enough for the actual state to matter.

For them to encode a photon on punch cards or carrier pigeon, they would have to observe it, so it would collapse. I have no knowledge of any way to send quantum uncertainty at the macro scale. As far as I know, it has to be a quantum-level object to stay a quantum function.

The whole thing is just creepy as hell, if you ask me.

Oh, and Caution: I don't think they could slow down time in one area without messing things up; it would fall out of sync with everything else. Of course, putting limitations on a godcpu might be foolish, but it seems to me that you'd need to emulate everything at the same speed, and when things got 'interesting', the individual frames for the whole universe would be slower, rather than for individual areas, to keep everything coherent.

It may, however, be foolish to try to put limitations on what a godlike intelligence and/or simulation program can do.

I'm almost sure I've said this before, but I think it would be very, very amusing if it turned the Universe really did start 6,000 years ago.... :)

By the way, Surfurrus, I forgot to say this earlier, but this was an awesome post. Thank you!
posted by Malor at 4:49 PM on August 25, 2008 [1 favorite]


bad science writing? :P

i was intrigued by the concept of unmeasuring something, like does that count as negative information? (don't get me started on negative probabilities ;)

btw, here's (probably!) a betr explanation of smith & yard's theoretical findings in quantum communication :D

cheers!
posted by kliuless at 2:54 PM on August 26, 2008


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