Researchers Identify 'Tipping Point' Between Quantum and Classical Worlds 83
wjcofkc sends this report from R&D Magazine:
If we are ever to fully harness the power of light for use in optical devices, it is necessary to understand photons — the fundamental unit of light. Achieving such understanding, however, is easier said than done. That's because the physical behavior of photons — similar to electrons and other sub-atomic particles — is characterized not by classical physics, but by quantum mechanics.
Now, in a study published in Physical Review Letters (abstract), scientists from Bar-Ilan University have observed the point at which classical and quantum behavior converge. Using a fiber-based nonlinear process, the researchers were able to observe how, and under what conditions, 'classical' physical behavior emerges from the quantum world.
Now, in a study published in Physical Review Letters (abstract), scientists from Bar-Ilan University have observed the point at which classical and quantum behavior converge. Using a fiber-based nonlinear process, the researchers were able to observe how, and under what conditions, 'classical' physical behavior emerges from the quantum world.
Quantum first post (Score:5, Funny)
You won't know if it's first until it's observed.... and it's not :(
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Funny considering that the post above yours is a classical first post from an AC troll.
Heisenberg compensator ... (Score:4, Interesting)
Will someone please tell me this gives us a basis for Heisenberg compensator?
Because that would be awesome.
I'm also hoping this whole thing "that, when unobserved, the photons exist in all possible states simultaneously" eventually goes away.
It has to be that we can't know what state it's in, not that it's actually in all of them. Can't it? Please? At some point, this quantum stuff should stop being magic.
Re:Heisenberg compensator ... (Score:5, Insightful)
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A complete conspiracy is itself a law of nature.
- Henri Poincaré
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Any sufficiently advanced technology is indistinguishable from magic. - Arthur C. Clarke
The fact that a person feels a phenomenon is beyond his comprehension doesn't alter the reality of the phenomenon. I know people who believe that Einstein's special theory of relativity is flawed. I have heard of others who believe rockets cannot fly in a vacuum because there is nothing for the rocket to push against. Still others insist that, "If men were meant to fly, God would have given them wings."
What was my point?
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What was my point? I forgot.
Any technology distinguishable from magic is insufficiently advanced.
Re:Heisenberg compensator ... (Score:5, Informative)
As far as I understand it:
The problem is that it is not in any one state, until observed. Then we just see a snapshot of our particular history that led to that observation. Observation determines the state but also modifies the system forever more, too.
One hypothesis of this leads to the "many worlds" interpretation" - it's in only in one state but until we actually look (and therefore modify the system) we don't (can't) know which particular universe of possibilities we happen(ed) to be in.
Unfortunately, quantum physics gets a lot weirder, which only serves to show us how little we know of it. I get lost in it as it's maths way beyond my capability nowadays (despite a maths degree), but as far as my friends in the research fields explain stuff, you can even get things such as particles "borrowing" energy from their future selves (at least, that's one hypothesis of what they are doing) - they don't have to energy to do X, suddenly they acquire it, then they always have pay it back afterwards. It only works if you consider time as "just another dimension" or if you include other spatial dimensions they could be getting this energy from.
Though we might be able to describe a convergence between classical and quantum mathematically (at some point in the future), the outcome is always going to be the same because we're just 4-dimensional creatures. Weird stuff is going to happen.
Physics is going to get a lot harder for us long before it gets any easier. Breakthroughs are few and far between and we're only now properly confirming stuff that was discovered / hypothesised in the 20's, 30's, 40's, etc. (don't forget, technically quantum mechanics goes back as far as the late 1800's!).
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*sigh* The more people try to explain it to me, the more it sounds like voodoo.
I understand the whole "measuring it changes it" thing ... but the rest of it? The whole "simultanously everything" thing just hurts my head.
It just sounds barking mad to a layman.
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I took quantum mechanics in college. I was going for a physics degree at the time. I struggled so much wrapping my brain around quantum mechanics that I dropped that as a major. (Instead, I went into computer science where I was picking up everything with ease.)
Re:Heisenberg compensator ... (Score:5, Funny)
Quantum physics used to confuse me too, but then I started smoking really good weed. Now, it is starting to make sense.
Seriously. Drugs can help you understand this stuff. I may need DMT to fully comprehend quantum physics, though.
Re:Heisenberg compensator ... (Score:4, Funny)
Having a 169 IQ helps too, but anyone can reach quantum visualization and comprehension this way. You still won't be able to explain it to most; it just doesn't sync with our macro experience. But you will grok it.
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DMT will just make you go really fast and THINK you understand it. Then you'll get all cranky and the Hippies will have to be nice to you until after you get some sleep because nobody else will.
There are limits to what "The Great God Rotor" can do.
Yours,
A Child of the 60s Who Actually Remembers
Comment removed (Score:5, Interesting)
Re:Heisenberg compensator ... (Score:5, Insightful)
You may be experiencing the difference between being very smart and being brilliant. I have run across this many times. When brilliant people agree and I don't understand the basics, I have to admit defeat, as if I were playing chess against a Grand Master.
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Warning: I'm a prrogrammer, not a physicist.
IIUC, one interpretation is that "yes, it's a particle, but it only has a probable location/velocity/momentum/etc.". So it is simultaneously both a particle (as an object) and a distribution of probabilities as characteristics of the particle. It's the probabilities that move as a wave, but it's only the particle that we can detect.
N.B.: I studied this quite a long time ago, so not only are things a bit fuzzy, the "best" way of looking at them may have changed
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I don't really understand it, but I've wondered if the wave/particle duality comes from the fact that quantum waves are like standing waves and have boundaries within which specific numbers of oscillation patterns can occur. Then waves give the uncertainty of oscillations, while the quantization gives the discrete particle behavior.
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Well there is always the "pilot wave" alternative. But it results in locality being violated, as a distant event can introduce changes to the wave that will then go on to influence results elsewhere.
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You think you have problems? I'm still trying to get my head around "It's both a particle... AND a wave!". How the f--- does that work? It doesn't even make any sense! It's insane! Wave things are not particles, and particle things are not waves!
Don't misunderstand our ability to comprehend something for the reality of the thing. We have tools for particles, we have tools for waves, so we see a thing and think "It's a particle! No, wait, it's a wave! That's weird, it's both!" In reality, it is what it is, regardless of our ability to comprehend it. In some sense there is no human-scale reality to these things, they are mathematical constructs of a certain sort, with interpretations that happen to simplify things in certain cases.
[When I say "h
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QA is well understood, well tested, well confirmed science but only when expressed mathematically.
As soon as we try to transform the math into English words like "wave", "particle" or "observer", we lose all the precision needed to adequately describe how QA works.
Re:Heisenberg compensator ... (Score:5, Interesting)
This is just supposition, but it's the way I choose to understand it. Note: This is probably not science.
Imagine you're a time traveller but in the classic Hollywood sense where timelines can be broken without the end of the universe, etc. Marty McFly doesn't have to worry about standing next to his former self and breathing in the oxygen he would have originally breathed in, etc.
You can go back in time, steal some cash from yourself, bring it back to a different timeline, use it to make yourself rich. It's all fine. So long as, at some point, you can back and put that money back for you to steal in the first place. This is similar to how particles they borrow energy. So long as nobody notices (in this case, so long as the energy is returned before the "uncertainty" in the uncertainty principle can be resolved), you're golden.
Additionally, you are both "in" the room stealing the cash and "out" of the room simultaneously at the same time because you've been jumping back and forth in time (and maybe even in the room watching yourself stealing the cash in order to put it back once you're gone). In one timeline, in 1956, you were there. In another, at the EXACT SAME TIME, you weren't. So asking "where were you at this exact time in 1956?" doesn't give a simple answer. I was here. I was there. I was not here at all. And I was all of them at the same "time".
Time is just a dimension, so it's one hypothesis that particles may well be doing exactly this - hopping back and forth through other dimensions of space (and thus disappearing from ours and reappearing somewhere else), jumping back and forth in time.
So long as they repay their debts, it all works out and doesn't violate (certain readings of) energy conservation laws. And particles aren't intelligent creatures that decide to do this, they may just be "things" bouncing through dimensions quite ordinary to themselves but "time", "parallel universes", "alternative histories" etc. to us. Following even the simplest of physical rules in those circumstances could look like the weirdest actions ever from certain points of view.
Imagine you're on a 2D universe, you are a piece of paper and cannot perceive things not on your surface. A "ghost-like" car tyre passing through your universe will come from nowhere, grow, change shape, look odd, etc. and then disappear and never have looked like a car tyre. Same kind of thing. If you can't perceive the extra dimensions, this horrible weird-shaped thing just pops into existence, wobbles about a bit as a strange-shaped silhouette, maybe forms a hole in the middle if it fell the right way, then disappears. Or maybe it fell perfectly straight and you ONLY ever perceived a rectangle-like shape coming and going. Same object, same thing happening, tiny change in parameters, totally different outcomes that are very unpredictable for you.
The problem with quantum stuff is that we just don't perceive other dimensions at all, but the maths does.
(x) describes how far along a ruler you are.
(x,y) describes where a pixel is on a 2D screen
(x,y,z) describes where you are in a 3D world.
(x,y,z,t) describes an EXACT point in space and the time you were there (e.g. your birth).
(x,y,z,t,q)? We have no way for you to perceive that. But mathematically it's just another co-ordinate.
Don't expect a layman to understand it. The geniuses don't understand it. They can describe it. They can measure it. They can produce the formulae. But, just taking the knock-on effects and working backwards, they'd have nothing. It's only because the maths comes up with weird outcomes and that we then FIND those weird outcomes in the universe that anything actually looks right. Trying to play it backwards from the weird outcomes to those formulae that you can't understand is never going to help you.
It's like being a blind man and wondering how people can know there's a silent car coming when you can only detect a car's sound. If you can't perceive entire dimensions that - we're pretty sure - are required to exist for quantum mathematics to work, then you're only ever going to see a third of the story (our current best guess is 11 dimensions - we think - as a minimum? So eleven letters in the above example!).
Re:Heisenberg compensator ... (Score:4, Informative)
11 dimensions is M-Theory, but if you go by Loop Quantum Gravity, you can formulate it in 3 or 4 dimensions.
There's really no theory that has "won" yet, so it is far too early to say there is a minimum number of dimensions.
Like you suggest, I believe that the "magic" of quantum effects would be a lot less "magical" if the objects in question could be described in at least one more dimension. The uncertainty principle is likely uncertain because you can have almost identical looking 4-D slices in a 5-D space. It only breaks down when you realize that certain objects or processes are prone to change much more extremely in higher-numbered dimensional space. So, if you fail to take 5-D into account, you can come up with a formula which seems to have two equally probable states, but in the end, of course, there was never any doubt.
For some value of 'q' the cat is dead and for some value of 'q', the cat is alive. Our current state of science is that we have equations that work very well with objects that are less variant in the 5th dimension than photons or quantum scale objects/processes are. Just like when we assumed that stars and mountains never changed or things didn't evolve because those processes are far less variant in the time dimension than the typical human lifetime.
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Re:Heisenberg compensator ... (Score:5, Insightful)
It just sounds barking mad to a layman.
Not just to a layman. To quote Richard Feynman: "I think I can safely say that nobody understands quantum mechanics."
And there are plenty more quotes in that spirit. [wikiquote.org]
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LOL, thanks ... that's actually somewhat reassuring. :-P
Re:Heisenberg compensator ... (Score:5, Insightful)
Consider this scenario. You are a two dimensional creature. You are only able to experience your reality as a flat plane. Up and down have no meaning to you; these are concepts quite beyond your comprehension. You cannot imagine a 3 dimensional object any more than we, in our 3 dimensional world, can imagine what a 4 dimensional object would look like.
Now, in your 2 dimensional world, creature, I, as a 3 dimensional God-like character, am going to take a circle, anything round, and shove it down through your plane of existence. What would you experience? You would experience at the very first, a single point suddenly appearing as if out of nowhere. This single point splits into two points that diverge from each other at a steady rate. Yet if I stopped pushing the ring through your plane for a moment and let you examine one of those two points that you can see, you would find that if you shoved on one point, the other point moved exactly the same. From my God-like perspective, all you did was shove the ring a bit. You, on your flat plane, see spooky action at a distance, because you're shoving one point and the other one is moving, too.
Given enough time and experimentation with these points that keep appearing in your plane of experience as I keep shoving rings and perhaps even more complex objects through your plane, you might even be able to come up with some really complicated mathematics and physics that describe all this bizarre motion and behavior in your 2 dimensional world. To you, it all appears incredibly complex and horribly incomprehensible, even utter nonsense, but you can manage to describe it in such a way that is at least consistent with the weird behavior you keep seeing. To me, in my 3rd dimension, I'm just chuckling over all that hard work you're going to, because to me it's just a simple ring I'm shoving through your plane and watching you go batshit crazy trying to figure out what's going on.
The point is simply that quantum physics appears bizarre to us because we are limited to experiencing 3 spatial dimensions and are forced to constantly move in a single direction on an axis of time. All the weirdness of quantum physics really just means that there are almost certainly many more spatial dimensions and more complete freedom of motion through time than what we are limited to experiencing. What you're seeing a lot of times is just the weirdness of seeing something that almost certainly "completely" exists in several more higher dimensions intersecting limited reality you are able to witness.
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To me, the weird thing is the notion that you could live in an N dimensional universe yet only be able to interact with N-1 of its dimensions.
The 2D person who cannot perceive up and down: both up and down are there and they produce various forms of inputs to the 2D world so how could he possibly not observe them?
What it is about the Nth dimension that makes it fundamentally impossible to observe directly?
With this concept being so weird it doesn't really explain anything for me wrt QM, it just adds a new q
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We can't see it but we can observe it, most significantly our skin reacts to it. The point of weirdness with the 2D example is that the third dimension is fundamentally unobservable, not that it's simply tricky to observe.
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Here's the youtube video:
https://www.youtube.com/watch?... [youtube.com]
I never understood quantum mechanics until I saw this video. Now it sort of makes sense. Of course much of it remains pretty mysterious, but the whole particle/wave duality thing? He explains it perfectly.
Feynman had an amazing gift for explaining hard scientific concepts to ordinary people without requiring maths.
Re:Heisenberg compensator ... (Score:5, Insightful)
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The universe is under no obligation to make sense to a bunch of shaved apes.
What if it is, but because we are a bunch of shaved apes we do not understand this?
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'No physical theory of local hidden variables can ever reproduce all of the predictions of quantum mechanics.'
In this case, local hidden variables refer to what you describe as it being in a single state and us just not knowing. Without faster-than-light information transfer (which we cannot have if causality is to hold within relativity), it is not possible that 'the system is in a state and we just don't know it. '. Quoting wikipedia,
In a theory in which parameters are added to quantum mechanics to determine the results of individual measurements, without changing the statistical predictions, there must be a mechanism whereby the setting of one measuring device can influence the reading of another instrument, however remote. Moreover, the signal involved must propagate instantaneously, so that a theory could not be Lorentz invariant.
This has been shown experimentally using Bell's equations and this work got him nominated for a Nobel prize but died before it was
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But redundant [wikipedia.org].
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I'm also hoping this whole thing "that, when unobserved, the photons exist in all possible states simultaneously" eventually goes away.
It has to be that we can't know what state it's in, not that it's actually in all of them. Can't it? Please? At some point, this quantum stuff should stop being magic.
Does it make you uncomfortable the idea that we are creating reality through our very consciousness? That sounds like woo-woo new-age shit, but one can interpret quantum mechanics in that way. The past and future do not exist except in our minds. The only time that truly exists is Now. Everything that has ever happened and ever will happen is happening now. We are choosing, through our consciousness, which part of that to experience.
Woo Woo! ;-)
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I'm also hoping this whole thing "that, when unobserved, the photons exist in all possible states simultaneously" eventually goes away. It has to be that we can't know what state it's in, not that it's actually in all of them. Can't it? Please? At some point, this quantum stuff should stop being magic.
To quote Richard Feynman:
I hope you’ll come along with me and you’ll have to accept it because this is the way nature works. If you want to know the way nature works, we looked at it, carefully, look at it and see... that’s the way it looks. You don’t like it? Go somewhere else!
To another universe! Where the rules are simpler, philosophically more pleasing, more psychologically easy. I can’t help it, OK! If I’m going to tell you honestly what the world looks like to the h
tl;dr? doesn't matter. those links don't answer... (Score:2)
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80 mW of pump laser intensity. I don't know how many photon pairs that generates in the photonic crystal.
Consequences for quantum computing? (Score:4, Interesting)
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If there is a size limit for a quantum computer, I wonder if you could get around this by having a large cluster of them. (Insert standard Beowolf joke here.) Have a classical computer break down the problem into components, send the components to the quantum computers, and then reassemble the results for the user.
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I don't think this work directly puts any limit on the size of a quantum computer. But the larger the computer, the harder it will be to keep the computer from coupling to environmental vacuum modes, which destroy the interference pattern.
At What Frequency? (Score:2)
Technics already did this: All radio/TV/radar transmitters and antennae do is change a stream of modulated electrons to similarly-modulated photons. At low frequencies (AM radio, as an example) the photons behave in a classical manner even being able to penetrate dense matter like buildings and mountains. At higher modulation frequencies, like FM or TV, this behavior is moderated, being blocked by physical obstructions; what's more the electrons which leave the transmitter travel not through the connecti
Re:At What Frequency? (Score:4, Informative)
That is not a correct description. Lower frequency radio waves are no less 'quantum' or 'classical' than higher frequency radio waves. AM radios can penetrate objects primarily because they have a wavelength on the order of 400 meters (up to around 1 MHz), whereas FM radios have a wavelength of only a few meters (through around 100 MHz). The longer wavelength of AM effectively allows the radio wave to bypass even relatively large objects such as mountains.
The same effect can be seen even within your house if you have a dual-band WIFI router. The 2.4 GHz band is able to penetrate walls and go around corners and reach the second floor far more easily than the 5 GHz band can.
-Matt
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And the difference in behavior of the transmission devices -- wires vs. wave guides -- is explained how?
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That is a totally different phenomenon.
A flock of starlings (Score:3, Interesting)
If you can't see the individual starlings, and can only see the flock, the flock behaves in a quantum manner. It jumps around, it can appear in two places at once, apparently traveling faster than light, it has probabilistic properties.
So the tipping point, depends on our detection technologies. If we can't zoom in to see the individual starling then quantum behavior is "flock of bird" sized!
Quantum physics does scale, you just need to realize that the 'flock' is the size that you can detect, and the reason you think it is one thing is because you can't detect half a thing. It's a function of the detector not the thing.
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If you can't see the individual starlings, and can only see the flock, the flock behaves in a quantum manner. It jumps around, it can appear in two places at once, apparently traveling faster than light, it has probabilistic properties.
So the tipping point, depends on our detection technologies. If we can't zoom in to see the individual starling then quantum behavior is "flock of bird" sized!
Quantum physics does scale, you just need to realize that the 'flock' is the size that you can detect, and the reason you think it is one thing is because you can't detect half a thing. It's a function of the detector not the thing.
Nope. You are suggesting a hidden variables theory where each starling is a variable. Bell's Theorem says that you can only have this if you give up locality, realism (counterfactual definiteness) or that the universe isn't just making it up as it goes along (conspiracy).
When there's enough matter involved? (Score:1)
translation (Score:2)
This experiment measures the power level where spontaneous emission becomes comparable to stimulated emission.
You have a similar situation in a laser. A laser works on the principle of stimulated emission. When you pass laser light of an appropriate frequency through an excited laser cavity, the light is amplified, since the light stimulates nearby particles to emit more light. So the light grows exponentially with the length of some cavity until saturating (by fully de-exciting the cavity). But, where does
Truly this is the darkest timeline. (Score:1)