Quantum Physics Questions

[dorion]

The observer in Quantum Physics speech who observes an event and causes the quantum state to collapse, doesn't have to be a person and could just be a piece of dirt being hit by a photon right?

Unfortunately this discussion has degraded into the arena of personal attack and thus has become derailed. This is NOT P & N folks! Thread is now locked. - Moderator Rubycon

 

[bsobel]

How do you know the photon hit the dirt without observing it?

Some people believe the universe requires an observer, its an open debate in QP what defines an observer.

 

[PowerEngineer]

I've been wrestling with the same conundrum while trying to understand the quantum eraser. As bsobel says, there is still an open debate around what it takes to be an "observer" capable of collapsing the quantum probability wave into a definitive spike.

The proposed explanation that makes the most sense to me (and is therefore almost guaranteed to be incorrect) is that anything able to interact with a particle is enough of an "observer" to force the collapse of its associated probability wave. For instance, an otherwise unobserved electron may not have to choose its location or velocity until it does (or doesn't) interact with a second electron (observed or unobserved). The need to deal with the (possible) mutual repulsion of their charges requires the unobserved electron(s) to more narrowly declare their positions (i.e. at least partially collapse their probability waves?). One pleasing outcome of this would be that the myriad interactions inside the mega-particle objects that fill our world will keep all their constituant particles'probability waves collapsed, which helps explain why their wave nature stays largely hidden from us (and why the particle-based classical physics works so well).

Okay, I probably butchered that a bit; I hope it helps anyway.

Back to the quantum eraser...

 

[dorion]

Seems I was right to be confused.

 

[Gibsons]

I think I can safely say that nobody understands quantum mechanics.

R. Feynmann, 1965

It might still be true today?

 

[f95toli]

The idea of an "observer" comes out of the Copenhagen Interpretation of physics, i.e. it is not in any way central to the formalism (as opposed to the interpretation) of quantum mechanics.
There has been a LOT of work done on decoherence in QM over the past 25 years or so and most of it has foccused on how to describe open dissipative systems; we have now reach a point where we have a pretty good understanding of what limits the coherence times (=how long the system stays "quantum") of many systems.
There is no "observer" in any of these theories, human or otherwise.

The idea of "quantum collapse" etc used to mainly a philosophical problem but nowadays it to some extent an engineering issue; short coherence times is what limits our ability to build e.g. quantum computers and other efficient quantum "devices". Most of these problems are not "fundamental" in any way, but are related to problems such as impurities in silicon (for solid state devices) or "noisy" lasers (for optics).

Note that I am not saying that we have "solved" the quantum measurment problem (i.e. what underlies the projection postulate); but there has been a lot of progress and we now know that there is no sharp "border" betweent the "quantum world" and the "classical world"; it is simply a question of coherence times.

 

[KIAman]

To the OP, yes, the observer does not have to be conscious.

To everyone else, take a look at Bell's theorem and forget true "reality."

IMO, the true issue of quantum mechanics is our lack of understanding and how to describe it. We are so closed-box around mathematics and "perfection" and "symmetry" that we attempt to describe reality around these concepts. We continue to think of particle, or point based, descriptors. This is convenient because it applies mathematically but it introduces too many paradoxes.

It is beyond me and everyone else (obviously) but until we re-think how to describe interactions at the quantum level, we will never surpass our current obstacles. How about wave and distance based effects? Is it possible quantum effects are just distance effects from the quantum source. Maybe it isn't even a distance effect, maybe it is direct effect given another dimension of interaction.

 

[Comdrpopnfresh]

Originally posted by: KIAman
To the OP, yes, the observer does not have to be conscious.

To everyone else, take a look at Bell's theorem and forget true "reality."

IMO, the true issue of quantum mechanics is our lack of understanding and how to describe it. We are so closed-box around mathematics and "perfection" and "symmetry" that we attempt to describe reality around these concepts. We continue to think of particle, or point based, descriptors. This is convenient because it applies mathematically but it introduces too many paradoxes.

It is beyond me and everyone else (obviously) but until we re-think how to describe interactions at the quantum level, we will never surpass our current obstacles. How about wave and distance based effects? Is it possible quantum effects are just distance effects from the quantum source. Maybe it isn't even a distance effect, maybe it is direct effect given another dimension of interaction.

Quantum states are a result of statistical probability related to quantum mechanics. As such, they exist in relation to a conscious observer.
Take Schrödinger's cat...
If a particle of dust lands on the box, it may kill the cat, or it may not- the state still cannot be determined but by an observer, and their observation collapses the state.
Throw a second cat in the box- it complicates the representative math of the quantum state, but the second cat is now immersed in the state- one cannot know if the second cat ended up killing the first (get's more complicated if the cats are indistinguishable haha).

The point is this- a quantum state is a 'flux' between more than one state. Any non conscious entity that interacts with what is in the state becomes an extension of it (either directly immersed, or to a 2nd degree). Therefore, if you observe the second object, it is an extension of you, the observer, and collapses the state just as you would. If you did not observe the second object's interaction with the first, you can't say anything further about the first object, and for all intents and purposes, the 1st+2nd is equivalent to the first. It's kind of like a system and surroundings in thermodynamics- If you're not in the surroundings, you're in the system.

 

[PowerEngineer]

It's my impression that probabilities used in statistics are essentially a convenient way of glossing over the many small or immeasurable influences that help determine the outcome of some physical process, such as flipping a coin. It's fair to say that if we carefully controlled and measured all aspects of each coin flip, we could accurately determine whether each would come out as heads or tails. But because we can't, statistics still allows us to say something useful about the likely distribution of outcomes for multiple coin flips (i.e. 50% heads and 50% tails).

It seems that the probabilities involved in quantum mechanics are fundamentally different. Rather than glossing over our lack of knowledge about the actual states of a small particle, the probabilities in quantum mechanics give us an indication of likelihood that the particle will assume that state when forced by "observation". It's not that there's an actual state we're just ignorant of; the actual state does not exist until measured.

This is what Bell's theorem/experiment proved (to most people's satisfaction).

Given the above, it's hard for me to believe that an observer of a particle needs to be "conscious". Would the whole universe work differently if we never existed? Or would dogs (or aliens) be "conscious" enough to keep it "as is"? It's my impression that even the possibility of being able to "observe" a particle's state from available measurements is enough to force it to "choose", regardless of whether or not anyone actually decides to look at those measurements.

My two cents (again)...

 

[Comdrpopnfresh]

The whole point is that those numerical statistics/probabilities of outcomes/states isn't of their current nature, but the likelihood of seeing them. The cat in the box may very well be dead even before we think of checking on it. The probability isn't of the cat actually being dead, but of observing that it is dead. No one there to observe, then the probability doesn't matter- it doesn't model what something is, it models what we would see. The numbers don't classify what it is, but what it may be if checked. It's not really real- it is a mathematical expression to illustrate the likelihood of an outcome pending action in our perception.
It's not like flipping a coin- whether someone flips it or not, if it were to be flipped, you'd have a 50% chance of getting tails (I think this is inline with your view). So it isn't that the statistics reflect that things wouldn't occur if we didn't exist, because the statistics are of the outcome of interacting, or interfering, with an object. See what I'm saying?

 

[Born2bwire]

Originally posted by: Comdrpopnfresh

Originally posted by: KIAman
To the OP, yes, the observer does not have to be conscious.

To everyone else, take a look at Bell's theorem and forget true "reality."

IMO, the true issue of quantum mechanics is our lack of understanding and how to describe it. We are so closed-box around mathematics and "perfection" and "symmetry" that we attempt to describe reality around these concepts. We continue to think of particle, or point based, descriptors. This is convenient because it applies mathematically but it introduces too many paradoxes.

It is beyond me and everyone else (obviously) but until we re-think how to describe interactions at the quantum level, we will never surpass our current obstacles. How about wave and distance based effects? Is it possible quantum effects are just distance effects from the quantum source. Maybe it isn't even a distance effect, maybe it is direct effect given another dimension of interaction.

Quantum states are a result of statistical probability related to quantum mechanics. As such, they exist in relation to a conscious observer.
Take Schrödinger's cat...
If a particle of dust lands on the box, it may kill the cat, or it may not- the state still cannot be determined but by an observer, and their observation collapses the state.
Throw a second cat in the box- it complicates the representative math of the quantum state, but the second cat is now immersed in the state- one cannot know if the second cat ended up killing the first (get's more complicated if the cats are indistinguishable haha).

The point is this- a quantum state is a 'flux' between more than one state. Any non conscious entity that interacts with what is in the state becomes an extension of it (either directly immersed, or to a 2nd degree). Therefore, if you observe the second object, it is an extension of you, the observer, and collapses the state just as you would. If you did not observe the second object's interaction with the first, you can't say anything further about the first object, and for all intents and purposes, the 1st+2nd is equivalent to the first. It's kind of like a system and surroundings in thermodynamics- If you're not in the surroundings, you're in the system.

You shouldn't be using Schroedinger's cat in this manner. The example is meant to show the disconnect between the quantum world and the macroworld that we observe. The idea of the cat being in a superposition of life and death is ludicrous.



.....



\shiftyeyes





Ludicrous Speed..... GO!

 

[WildW]

I'm always daunted at the notion of even posting on Highly Technical, but my own personal thoughts on Observers in this context are like this. . .

I watch my friend toss a coin and catch it, concealing it under their hand. I can see their hands flat together so I reason it has landed either head or tails up. Nobody has seen the result so in typical QM fashion either state is possible.

My friend lifts their hand, peeking at the coin just enough to tell which way it has landed, but so that I can't see the result. They have observed it, so, the state collapses and the coin now has a definite head or tails state.

Except, it hasn't. From my perspective I have no more information than I had before my friend looked. Even if my friend tells me, they could be lying. The only way to know the result for sure is for me to look at it directly. From my perception, my friend therefore doesn't count as an observer. I am the only observer that matters to myself. This is the only way of reasoning QM that I can get my head around. . . but it does make the world a very lonely place, knowing that nobody else is real.

And you are all just subroutines in the internet's web-forum program until I meet any of you.

 

[Aberforth]

Some of the users are highly technical- they live their lives on books and take the authority of such information for granted then there are people who know very little but they are curious to learn more in order decipher the mysteries of this universe. And finally, there are people like me who have outgrown both of these stages. quantum theory is very old, in fact Sir Issac Newton had a very crude idea of it but for some reason he doesn't get the credit.

During my research I've found that Time and Space are two things that exists in our minds not anywhere else- within us the universe exists not outside, this shouldn't be confused with fantasy or imagination- especially when we are talking about quantum mechanics. We have our own micro universe, for example: consider thought A and thought B, the distance between A and B would be the Absolute Space and the time taken to reach from A to B is the Absolute Time, so any other means of external observation would be inaccurate and unpredictable. Why shouldn't this be true? we exist in the same universe and we are a part of it's creation, to decipher it we have to analyze our own nature and limitations. Our bodies are made up of same quantum particles in motion as the rest of the nature, everything that is matter has a shelf-life and is constantly aging or is it really? No, only the flux is constantly changing coupled with the flux in the mind so the observer is being deluded continuously throughout his life by the various states of this flux. Let me give you a simple example: consider a empty building site where there is no structure but the material and force required to build the structure is already there- but it has not yet taken a definite shape for it to be recognizable for humans, so the building materials should be bought into such a state of vibration of particles where humans can recognize it as a structure. This just tells us that sense organs and perceptions are highly unreliable, mind is trying interpret false projections. This is exactly why we build telescopes and microscopes to observe the farthest and the closest and many other spectral instruments. Maybe nothing is real- how reliable is the human mind? it might not be functioning correctly which is exactly why we depend on external instruments- how do you know everything you see exists? Maybe it doesn't. So I do not take the authority of such sense observations for granted. The universe isn't real, it is only composed of quanta acting in a certain shape and frequency allowing us to discover purpose in order spend vast amounts of free time in a wild goose chase.

 

[KIAman]

^ Just a friendly suggestion. Instead of the mental diarrhea, why not organize your thoughts a little so we can better understand your point?

 

[Aberforth]

Originally posted by: KIAman
^ Just a friendly suggestion. Instead of the mental diarrhea, why not organize your thoughts a little so we can better understand your point?

My point is - sense perceptions are not real. Theories/Laws interpreted and observed by sense organs are as flawed as the sense organs themselves. Whenever I suggest something controversial I attract criticism about my spelling and grammar - it's so funny. I know am not wrong, you guys are just too......external.

 

[silverpig]

Originally posted by: WildW
I'm always daunted at the notion of even posting on Highly Technical, but my own personal thoughts on Observers in this context are like this. . .

I watch my friend toss a coin and catch it, concealing it under their hand. I can see their hands flat together so I reason it has landed either head or tails up. Nobody has seen the result so in typical QM fashion either state is possible.

My friend lifts their hand, peeking at the coin just enough to tell which way it has landed, but so that I can't see the result. They have observed it, so, the state collapses and the coin now has a definite head or tails state.

Except, it hasn't. From my perspective I have no more information than I had before my friend looked. Even if my friend tells me, they could be lying. The only way to know the result for sure is for me to look at it directly. From my perception, my friend therefore doesn't count as an observer. I am the only observer that matters to myself. This is the only way of reasoning QM that I can get my head around. . . but it does make the world a very lonely place, knowing that nobody else is real.

And you are all just subroutines in the internet's web-forum program until I meet any of you.

That's not quite right though. If you read f95toli's post you'll see that a quantum state is only coherent for a short period of time. What this means is that you can set up a quantum state and it will evolve predictably according to QM until it decoheres. This decoherence is essentially the name given to what happens when the state interacts with its surroundings and takes on certain properties of those surroundings, thus destroying the state.

Quantum superposition of states isn't just cheap cop-out of the "I haven't looked so I don't know" situation.

 

[KIAman]

Originally posted by: Aberforth

Originally posted by: KIAman
^ Just a friendly suggestion. Instead of the mental diarrhea, why not organize your thoughts a little so we can better understand your point?

My point is - sense perceptions are not real. Theories/Laws interpreted and observed by sense organs are as flawed as the sense organs themselves. Whenever I suggest something controversial I attract criticism about my spelling and grammar - it's so funny. I know am not wrong, you guys are just too......external.

I apologize if I've offended you (or in this case, made you laugh), but as the "communicator" with "information" you should apply due diligence to make sure your "message" is easily understood.

I've read all your other stuff and it's not nearly this bad. Don't assume anything based on history, there is none. Besides, nothing in my statement included the words "you are wrong because..." It did assume you WANT people to understand what you are writing.

After digesting everything you've written, you are asserting nothing is real until it has been perceived BUT because our own senses are flawed, everything is real and our interpretations are wrong?

 

[PowerEngineer]

To Comdrpopnfresh: I'm having a hard time reconciling the statement in your first post which seems to suggest (at least to me) that the "flux" between quantum states exist in relation to a conscious observer with the statement in your second post which seems to concede that "outcomes" (which I interpret to be the particle taking on a specific state) would take place without a conscious observer. I guess my understanding is still in a state of "flux".

To WildW: The interesting thing about the uncertainty/probability in quantum mechanics is that it is fundamentally different from the uncertainty you describe in your coin flip example. It goes beyond individual ignorance of what state (heads or tails) the coin has already taken under your friend's hand. It is that the coin has neither state until it is forced by observation to assume one. The Bell experiment mentioned earlier demonstrates this amazing result. Now I'm not trying to pooh pooh your point about you being the only reliable observer (while I restrain myself from mentioning magic tricks and opitcal illusions); I'm just pointing out that your view is not tied to quantum mechanics. And I hope you find me an interesting subroutine.

To Aberforth: I had to chuckle while reading your first post because it reminded me of what Captain Kirk always heard from some seemingly backward alien before he/she transmuted into the higher-plane energy being that was way beyond what poor human beings could comprehend. From your second post, I gather that you question the reality of what we perceive through our senses. I'll agree that there's no way to prove that our senses are completely accurate. In fact, there are many studies that show just how easily our senses can fool us (if you can believe your eyes while reading them). And then there are the people who have been abducted by aliens... On the other hand, our senses are "the only game in town". If we have to discard everything our senses tell us, then there's nothing for us to talk about -- certainly nothing for us to agree on. We can all continue "research" into our individual imaginary universes. Think I'd rather gamble a bit and take as a postualte that our senses are an (imperfect) window on reality. No offense (if you are one of those energy beings) :sun:

 

[Aberforth]

Originally posted by: KIAman

Originally posted by: Aberforth

Originally posted by: KIAman
^ Just a friendly suggestion. Instead of the mental diarrhea, why not organize your thoughts a little so we can better understand your point?

After digesting everything you've written, you are asserting nothing is real until it has been perceived BUT because our own senses are flawed, everything is real and our interpretations are wrong?

Nothing is real until it is observed in it's original state- so you have to dive into quantum state to understand it precisely, any other higher state is filled with half-truths because the observation is partial and one-dimensional. That's is when you disconnect senses and bring your mind into such a state where you can identify the real nature. There is a way to do this through meditation, ancient Indian and Greek philosophers usually observed this way. Is it a hypnotic state where you see winged creatures from heaven? No, it assumes you are already hypnotized and the mental experiments are all about de-hynotizing yourself. But the problem is there always a spiritual aspect associated so scientists choose to ignore it. PM me if you are interested, it's not at all wise to mention it here

 

[iCyborg]

Originally posted by: dorion
The observer in Quantum Physics speech who observes an event and causes the quantum state to collapse, doesn't have to be a person and could just be a piece of dirt being hit by a photon right?

Whether the observer has to be conscious depends on the QM interpretation as some people above have already mentioned.
Just want to chip in and say that R. Penrose has a theory that quantum state collapses on its own if enough matter is involved, enough being around Planck's mass which is not that small, about a speck of dirt/dust (10^-5 grams).
Bear in mind that while Penrose is a very well regarded physicist, this theory of his isn't

 

[Comdrpopnfresh]

Originally posted by: PowerEngineer

To Comdrpopnfresh: I'm having a hard time reconciling the statement in your first post which seems to suggest (at least to me) that the "flux" between quantum states exist in relation to a conscious observer with the statement in your second post which seems to concede that "outcomes" (which I interpret to be the particle taking on a specific state) would take place without a conscious observer. I guess my understanding is still in a state of "flux".

The thing about quantum mechanics is that as long as you don't violate something, and follow the rules/procedures... a number of (philosophical, or qualitative, shall we say?) interpretations can be applied, and each is just as right as the other- honestly, because it doesn't matter. If something is in a quantum state, we cannot define the state any further for whatever reason. This is where the What and the Why diverge: We know What we don't know, and statistically lay out What we can suspect/assume. The Why's are all equally valid, and useless, as long as they don't preclude anything in the What:

Okay... state of flux... Must be occupying more than one state at the moment, but this flux will collapse when we try to find out... Obviously has a well defined state in a local hidden variable we do not know, so we must tag it with probable states we cannot confirm because we can't access that variable.... etc.

As long as we all agree on what we cannot know, it doesn't matter your reasoning- when you have any interaction with w/e is in a quantum state, it adheres to a defined state- everyone's hypothesis of what is going on before has no more bearing, and we are all in agreement from there on. If I say it has a well defined state from an absolute reference frame but we, not residing in such a frame, cannot know what it is: or if you say it occupies many states equally until we do something that demands a state and the quantum state collapses to a defined state: or someone else says it has no state until we observe one- it does not matter, they all end upon the collapse of the quantum state, which occurs with an interaction.

This is all further congested by thought experiments, of views thereof that don't align. Sticking a video camera in the box with the cat- can set off the isotope and kill it... because we were watching.....and how would you get the camera in there in the first place? How do you know if a piece of dirt is hit by a photon?-you don't, so you can hypothesize what happens from there to the first observation... it makes no difference- upon observation, a state is defined.

Quantum state -> observation -> collapse -> defined state

 

[Aberforth]

Originally posted by: Comdrpopnfresh

Originally posted by: PowerEngineer

To Comdrpopnfresh: I'm having a hard time reconciling the statement in your first post which seems to suggest (at least to me) that the "flux" between quantum states exist in relation to a conscious observer with the statement in your second post which seems to concede that "outcomes" (which I interpret to be the particle taking on a specific state) would take place without a conscious observer. I guess my understanding is still in a state of "flux".

Quantum state -> observation -> collapse -> defined state

Thanks for explaining this in one line.

 

[PowerEngineer]

Originally posted by: Comdrpopnfresh
As long as we all agree on what we cannot know, it doesn't matter your reasoning- when you have any interaction with w/e is in a quantum state, it adheres to a defined state- everyone's hypothesis of what is going on before has no more bearing, and we are all in agreement from there on. If I say it has a well defined state from an absolute reference frame but we, not residing in such a frame, cannot know what it is: or if you say it occupies many states equally until we do something that demands a state and the quantum state collapses to a defined state: or someone else says it has no state until we observe one- it does not matter, they all end upon the collapse of the quantum state, which occurs with an interaction.

If I understand you correctly (there's always a first time ), you are saying that there's no way of telling whether a characteristic of an unobserved (i.e. coherent?) particle has a determined but unknown state before we observe it, or instead that it has some sort of indeterminate state until we we observe it. And there's no point in taking a stand one way or the other because it's unknowable almost by definition. What can you possibly hope to know about the characteristic of a particle before you measure it?

As reasonable as that seems, it turns out that there is a way to tell the difference. Bell's experiment (referenced earlier) seems to show that the latter is definitely the case in quantum mechanics. A truely stunning result.

 

[silverpig]

Uh, how many people in this thread actually have physics degrees?

 

[Comdrpopnfresh]

Do you have an english degree? Would you say you are qualified enough in computer science to use the interwebs?