Slashdot Mirror
Researchers Identify 'Tipping Point' Between Quantum and Classical Worlds
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.
classical frist psot
You won't know if it's first until it's observed.... and it's not :(
Live today, because you never know what tomorrow brings
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.
Lost at C:>. Found at C.
Sincerely,
Your Sobernost Mentor
the original question: At what point, of photon flux, (one presumes), is the cross-over between observed quantum and classical phenomenon? none of those ('advertising') links answer the question. So make up your own number, there will be a constrained uncertainty to it anyway ("42"?)
It'll be interesting to see what consequences this result will have on quantum computing. If the tipping point between the quantum and the classical world is something fundamental to physics and cannot be overcome, that means there is a limit to how big quantum computers can be. And if there is such a limit, will the largest possible quantum computers be any useful or does it mean that the whole field of quantum computing amounted to nothing?
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 connecting copper cables, but on the surface only, which is why those connections are straps and not thick wire. At ultra high frequencies like radar, wave guides are used, as the stream of electrons behaves nearly exactly like light. And as we can deduce, radar is useful because the photons are reflected with very high efficiency.
Perhaps this is the explanation of this phenomenon. I dunno, cause the abstract provides no information on what frequencies were used.
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.
Wouldn't it make sense to the quantum/classical crossover to be when the number of particles is high enough for them to constrain each other's wacky quantum behavior? I bet that's also the point when the total gravitational field overwhelms the stronger forces.
Stop saying 'entangled photon pairs'. Nature does not work that way. No useful tech will be build relying only on 'pairs'. Quantum computers will rely on multiple particle entaglement.
80 mW of pump laser intensity. I don't know how many photon pairs that generates in the photonic crystal.
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 the initial "seed" light come from in a laser? The laser cavity also emits light via spontaneous emission. So what you have is some combination of spontaneous and stimulated emission. The stimulated emission ramps up exponentially and dwarfs the spontaneous emission, which is always present.
Stimulated emission can be treated using classical mechanics by treating the medium as an amplifier. But spontaneous emission must be treated quantum mechanically. Of course, stimulated emission can also be treated with quantum mechanics. So quantum mechanics is valid all the time, but classical mechanics is only valid above a certain point.
a "fiber-based nonlinear process"
Sounds stringy.
Well, As a Physicist, I understand the difficulty of grokking QM. However, most of the confusion results from mistaking the physical reality with the mathematical spaces in which QM is both described and calculated... Drugs are not needed, but can be useful if trying to break down the barrier between concrete and abstract thought. Beer is probably better, with a perfect head...
There is also the confusion spread by scientists that half-understand what they are spouting... And the tendency to use the latest buzz-words adds more confusion.
All it takes is absorbing mathematics through a sharp pointed pencil or pen ( for the brave and paper-rich ), then connecting that to reality. But there is a caveat - QM is a bit incomplete. There are some major philosophical controversies that point to missing elements ( do your owm research on that ) which means it is a cute approximation.
Fairly good, but still an approximation.
Then there is the bottom line - for all physics above SR and E&M - what is the electron?
Until that is solved, all of the strange things are merely curiosities. Even the 'GOD Particle'....
It's turtles, all the way down.
Shouldn't have rolled the dice, Jeff.
Firstly it is not an hypothesis, it is an interpretation due to the lack of possibility to falsify this (the universes are not supposed to interract - i know that some people have posited that if brane exists and interract, some trace msut be found, but AFAIR the article are speculative and do not propose a real way to falsify the hypothesis). Which is why we have right now the MW itnerpretation and the collapse interpretation. because both are attempt at explaining 8or not explaining) what we observe mathematically *seem* to happen.
The main reason I dislike MW interpretation, is mostly due to the fact that you run into multiple problem if you think about it. Problem : divergence. Very quickly universe would diverge wildly into an infinity of possibility. Think about it : that wave function has a very low probability to enter state which makes go into a reaction with the environment or ionize , which would not happen in other universe, but does in this one. So you are positing that the divergence happens at the measurement, which brings up all sort of pointed question, like how those energy making up the universe are coming from, and from a conservation of energy point of view make no sense, or your argue that energy is not conserved and universe can pop into existence without a problem which bring far more question up. So you can solve this with another : you posit that those infinite universe *always* existed and we are simply in a very small subset of universe where the measurement happen. But if you start that way, it does not explain WHY there would be a universe at all where the measurement would be different than ours. Sure there is an infinite amount of universe, but WHY would the number of universe where the measurement occurs exactly match the probability we see ? On the intellectual level it makes as much chance as magic.
MW interpretation makes not much sense to me. At least collapse does not make up an infinity of universe following measurement distributions rules. It is a pure mathematical artefact, but it is far far better to admit "yeah I don't know, copenhagen interpreation does not explain anything but it does not make a bunch of stuff up either".
I can visualize it, but only in a way I know deep down is wrong
I have been wondering the same for years. Until I saw this.
It's based on the Pilot Wave interpretation of Quantum Mechanics. You can learn more here http://en.wikipedia.org/wiki/Pilot_wave.
Hahahahaha..... silly rabbit!
Not weed!
First they have to find you, bring you to the room, and offer the red pill OR the blue pill.
You have to take both, somehow.