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entropy1
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I heard from many sources that quantummechanics is purely random in nature. Has this been demonstrated?
If so, what is the proof?
If so, what is the proof?
1) Scientists (mostly on the internet).micromass said:1) What sources?
2) What do you mean with purely random? Or what do the sources mean with it?
An answer to your question depends very heavily on this.
entropy1 said:1) Scientists (mostly on the internet).
micromass said:You'll need to be more specific. This forum finds statements of right sources very important.
entropy1 said:I understand that. Unluckily, I can't recall my sources. Is it possible to consider my question as-is?
(I will try to retrace my sources)
Yes, I know. But he makes fun of a "pompous philosopher" at the end. I was referring to that segment.vanhees71 said:Feynman would be very upset if he's know that you say his remarks are "philsophical" ;-). SCNR.
Good question! That is what I don't know! I thought other people were proposing it! If so, I'd like to know how they come to that!DrChinese said:What would it take to convince you something is "really random" - past it appearing random and there being no currently known causes?
entropy1 said:Good question! That is what I don't know! I thought other people were proposing it! If so, I'd like to know how they come to that!
Perhaps I could add: How can we demonstrate that (for instance) collapse is not 'induced' by 'other causes'?
The randomness follows directly from the axioms of quantum mechanics, and in that sense it is dictated by the math. However, it is possible that there is more to it; it might be that the axioms could be derived from some deeper underlying theory that we don't yet know. That hypothetical deeper theory need not involve randomness. (An analogy: I get excellent agreement with experiment using the axiom "When tossed, my coin will randomly come up heads or tails with 50% probability each way" but the behavior of the coin is governed by deterministic Newtonian mechanics).entropy1 said:What I would like to know is if the math is also dictating that for collapse! That is, do we know there is absolutely no physical cause determining the outcome of a collapse?
It does seem odd, or at least at odds with our classical intuition. That's the motivation for looking for a deeper underlying theory in the first place. However, we have to find one before we can sensibly talk about it.And even if there is no physical cause for collapse, there still is a correlation between outcomes of collapse. Could this correlation be described in terms of hidden variables? It seems odd that there even is a correlation if there doesn't exist a mechanism to produce it.
DrChinese said:But this common view would be updated were there to be evidence to the contrary in the future. Presumably that would mean that Bohmian non-locality was specifically demonstrated.
So non-randomness is not yet ruled out, I understand? Then there would be no evidence for randomness yet, as I take it.Nugatory said:However, it is possible that there is more to it; it might be that the axioms could be derived from some deeper underlying theory that we don't yet know. [..] It does seem odd, or at least at odds with our classical intuition. That's the motivation for looking for a deeper underlying theory in the first place. However, we have to find one before we can sensibly talk about it.
entropy1 said:1. So non-randomness is not yet ruled out, I understand?
2. Then there would be no evidence for randomness yet, as I take it.
But can you assert that just because something (ie. collapse) is behaving randomly, it is in its nature random? (I hope I am not getting too philosophical here)DrChinese said:There is no end of evidence for randomness in the quantum world, and no evidence for any hypothetical underlying cause to explain such events. So I disagree with your 2.
Or to put it on another level: there is equal evidence for an underlying cause for apparent quantum randomness as for the existence of unicorns and mermaids. As far as I know, nothing could rule out the future discovery of non-local hidden variables (your 1).
This is a highly philosophical question on what randomness is, rather than the mathematical concept. It reads a little bit like you were looking for evidence to support an ideological point of view, rather than evidence for insights.entropy1 said:So non-randomness is not yet ruled out, I understand? Then there would be no evidence for randomness yet, as I take it.
Nugatory said:An analogy: I get excellent agreement with experiment using the axiom "When tossed, my coin will randomly come up heads or tails with 50% probability each way" but the behavior of the coin is governed by deterministic Newtonian mechanics
DrChinese said:Or to put it on another level: there is equal evidence for an underlying cause for apparent quantum randomness as for the existence of unicorns and mermaids.
I was expecting a remark of this kind (with all due respect). I conclude one is free to take either side, given good arguments. There are many good arguments to defend randomness, and none to defend non-randomness (HV).fresh_42 said:This is a highly philosophical question on what randomness is, rather than the mathematical concept. It reads a little bit like you were looking for evidence to support an ideological point of view, rather than evidence for insights.
I will confess right here my reason for wondering about the answer to my question: I, personally, have a hunch that the apparent randomness is in fact apparent, and can be described by non-random factors. However, I know very little of the matter, so I wanted to have my hunch ruled out to get rid of it. I can't help having the hunch. I deliberately am trying to be very careful with my words here, but that is the reason. I'm sure pretty much of the work has been done already by brilliant minds, of which I am not one, for all that matters.fresh_42 said:Whether you call it true or not simply isn't relevant. Nobody cares.
entropy1 said:But can you assert that just because something (ie. collapse) is behaving randomly, it is in its nature random? (I hope I am not getting too philosophical here)
entropy1 said:I will confess right here my reason for wondering about the answer to my question: I, personally, have a hunch ...
DrChinese said:Sure I can assert it. That is what evidence is for.
That was really helpful!atyy said:Quantum mechanics is not random in "nature". If nature exists, then it is nonlocal.
However, quantum mechanics is "operationally" random, since it does not allow information to be sent faster than light.
Both are important consequences of the fact that quantum mechanics predicts that experiments can violate Bell's inequality. The consequence of nonlocality in nature is that new physics probably exists. The consequence of operational randomness is that we can use quantum mechanics to guarantee randomness for cryptography, provided we believe that our adversary cannot send information faster than light.
entropy1 said:It occurred to me that randomness maybe can't be proven except for its (random) behaviour. So (many) indications for random behaviour would make a strong case.
However, wouldn't it be a circumstantial one?
I think I get that. However, suppose that, in an entanglement experiment with polarizers and photons, we could align the polarizers perfectly. The correlation of photons both passing their polarizers would be 100%, right? Of course we can't predict if the photons are going to pass, but we know that if one has done so, the other will do too! (in this setup) This would almost be a law! So I can imagine that the statistical construct of QM could have deterministic properties!The Bill said:It's only as circumstantial as any opinion based on statistical evidence is. In fact, all evidence we have of the workings of the universe are statistical in nature.
For example, you probably think it's close to certain that if you set a light wooden cube gently on the center of an IKEA tabletop that the cube won't fall through the table. However, that impression is just based on your statistical evidence that every time you've set a small stable object gently on a table, it has stayed on top of the table. You might think you have a lot of evidence for this, but the number of times you've set things on tables is certainly fewer than the number of quantum mechanical events which have been precisely measured by human scientists.
entropy1 said:I think I get that. However, suppose that, in an entanglement experiment with polarizers and photons, we could align the polarizers perfectly. The correlation of photons both passing their polarizers would be 100%, right? Of course we can't predict if the photons are going to pass, but we know that if one has done so, the other will do too! (in this setup) This would almost be a law! So I can imagine that the statistical construct of QM could have deterministic properties!
I think I get that.DrChinese said:This logic is a rollback to EPR in 1935. That part is very reasonable. It is the Bell part that tears this view apart. As I have said several times in this thread: if you want determinism, you get nonlocal action at a distance as part of the bargain.
That is of course true. However, I see it differently: suppose the angle is not 0°, but, for instance 10°. I can interpret that as the "gun pointed 10° off axis". The "balls" could hit target randomly, or they could do so deterministicly as part of the setup. The variables have to be non-local.DrChinese said:Keep in mind that the "law" is the cos^2(theta) relationship, which can be 100% at appropriate angles. There is nothing about that which requires anything to be predetermined because of that particular value.
entropy1 said:I think I get that.
That is of course true. However, I see it differently: suppose the angle is not 0°, but, for instance 10°. I can interpret that as the "gun pointed 10° off axis". The "balls" could hit target randomly, or they could do so deterministicly as part of the setup. The variables have to be non-local.
I take it you disagree. Is it a matter of preference?
Ok. You're in good company saying a thing like that to me. Apparently I was not as clear as I hoped to be. Maybe I do not understand this matter. Thanks for the insight.The Bill said:I suggest you watch some of Leonard Susskind's lectures on entanglement on Youtube, study the problem for a while in your textbooks, then come back and see if you understand it a bit better.
entropy1 said:The correlation of photons both passing their polarizers would be 100%, right? Of course we can't predict if the photons are going to pass, but we know that if one has done so, the other will do too! (in this setup)
Quantum mechanics is a branch of physics that studies the behavior of matter and energy at a very small scale, such as atoms and subatomic particles.
Quantum mechanics is considered random because it describes the behavior of particles in terms of probabilities rather than definite outcomes. This means that it is impossible to predict the exact location or behavior of a particle, only the likelihood of it being in a certain state.
Classical mechanics describes the behavior of macroscopic objects, while quantum mechanics describes the behavior of microscopic particles. In classical mechanics, the behavior of objects is deterministic, meaning that it can be predicted with certainty. In quantum mechanics, the behavior of particles is probabilistic and cannot be predicted with certainty.
The uncertainty principle states that it is impossible to know both the position and momentum of a particle with absolute certainty. The more accurately we know one of these properties, the less accurately we can know the other. This is a fundamental principle in quantum mechanics and is a result of the probabilistic nature of particles at the subatomic level.
Quantum mechanics is used in a variety of technologies, including transistors, lasers, and computer memory. It also plays a crucial role in fields such as cryptography and quantum computing, which have the potential to greatly impact our daily lives in the future.