What is Meant by Measured in the Context of Electron Position?

[Ken Ucarp]

When we say, for example, an electron does not have an exact position around an atom until it is measured, what is meant by measured? Certainly it can't simply mean measured by a human. I'm guessing it means measured in the sense of interacted with by another system. And if that's the case, when is an electron NOT interacting with another system? Isn't it in constant interaction with its atom? And if THAT's the case then it's position is fully determined at all times. We humans may not know what it is, but that doesn't mean it's not fully determined.

 

[phinds]

When we say, for example, an electron does not have an exact position around an atom until it is measured, what is meant by measured? Certainly it can't simply mean measured by a human. I'm guessing it means measured in the sense of interacted with by another system. And if that's the case, when is an electron NOT interacting with another system? Isn't it in constant interaction with its atom? And if THAT's the case then it's position is fully determined at all times. We humans may not know what it is, but that doesn't mean it's not fully determined.

Yes, as you surmise it means interaction w/ something. No, it is not interacting with the atom in that sense and no, its position is NOT determined at any time other than interaction.

 

[Ken Ucarp]

Well ok, then is there a time when the electron is not interacting with anything at all? And if the electron isn't interacting with the atom, then how is it that it's associated with the atom and not just free floating so to speak? The Coulomb force is the agent of interaction between the electron and its atom, isn't it?

 

[StevieTNZ]

We have no solution to the measurement problem for standard QM (versus Bohmian Mechanics), so anything that deals with answering about observations to make a potentially become an actuality (e.g. from superposition of states to one state) is, at this time, a guess.

 

[Ken Ucarp]

Interesting. I just read the post entered several minutes after mine about Measuring and Collapse. It's funny how both posts are asking the same thing, but one (the other, not mine) seems to get into technical details that to me just cloud the issue. It seems like the bottom line is, QM is all about our human ability to measure systems, nothing more. So it's really about the limits of human understanding, not necessarily the nature of the world.

 

[Ken Ucarp]

We have no solution to the measurement problem for standard QM (versus Bohmian Mechanics), so anything that deals with answering about observations to make a potentially become an actuality (e.g. from superposition of states to one state) is, at this time, a guess.

But what exactly is potentially? That just seems to be another way to say we as conscious observers don't know. So it seems like somebody made the misstep of projecting our lack of observing onto nature itself. I.e. just because to us it's a potentiality doesn't mean it actually is. It could be fully determined, just we'll never know it.

 

[StevieTNZ]

But what exactly is potentially?

My apologies - I meant to write potentiality.

If we use Schrodinger's cat as an example, the famous |alive> + |dead> is the superposition state. It is in neither state, in a classical sense. But the cat has the potential to become |alive> OR |dead> upon 'observation'. What counts as observation is again subject to debate and guesses at the moment.

 

[Ken Ucarp]

Ya the spelling of the word wasn't important. Whatever we mean by observation/interaction, my question is, can a system/particle exist without any interaction/observation whatsoever? "To exist is to interact" - Ken UCarp, TM 2017 :)

In the cat analogy (and I know this is sounding funny as an analogy, but we know we can translate the example into something more realistic) what's the status of the cat? It surely knows if it's alive, even if before we open the box we don't know. This to me means the example, and the issue in general is NOT about observation or measurement. I.e. whether or not we're able to observe the cat by lifting the lid has nothing to do with the state of the cat itself. So why does everyone seem to think it does? Why the fancy talk about "superposition" and the cat being dead or alive (or the electron having this or that specific location). Like I said, it seems somebody is projecting something about our ability to observe onto the nature of the universe.

 

[Mentz114]

Ya the spelling of the word wasn't important. Whatever we mean by observation/interaction, my question is, can a system/particle exist without any interaction/observation whatsoever? "To exist is to interact" - Ken UCarp, TM 2017 :)

In the cat analogy (and I know this is sounding funny as an analogy, but we know we can translate the example into something more realistic) what's the status of the cat? It surely knows if it's alive, even if before we open the box we don't know. This to me means the example, and the issue in general is NOT about observation or measurement. I.e. whether or not we're able to observe the cat by lifting the lid has nothing to do with the state of the cat itself. So why does everyone seem to think it does? Why the fancy talk about "superposition" and the cat being dead or alive (or the electron having this or that specific location). Like I said, it seems somebody is projecting something about our ability to observe onto the nature of the universe.

The reason for the fancy talk is that the formalism allows superpositions of states (like harmonics in a guitar string) and a lot of people think that nature acts like that all the time. Superpositions are a fact but only in some specific instances.

 

[Khashishi]

The answer depends on which interpretation of quantum mechanics is "right", if it is even possible to determine.

And if that's the case, when is an electron NOT interacting with another system? Isn't it in constant interaction with its atom? And if THAT's the case then it's position is fully determined at all times.

It's not enough for an object to interact with another object to collapse the wavefunction. In the case of an electron interacting with a nucleus, this puts certain constraints on the motion of the nucleus and electron (they together orbit each other, conserving energy and momentum), but the state of the full atom is still uncertain. By the second law of thermodynamics, entropy can't decrease when two objects interact. So if a nucleus recombines with an electron, the new atom must contain more uncertainty in its state than the uncertainty in the original electron and nucleus.

Because of the second law, it's not possible to measure the state of something unless it interacts with something larger which acts like an entropy sink. In a quantum experiment, the object under measurement is microscopic, and the detector is some large macroscopic thing with an absurdly large number of quantum states. A measurement is possible because the detector has a set of measurement complete states which give information about the object under test but it takes energy to run the machine, so entropy was increased somewhere.

In other words, to act as an "observer", a device has to be able to move entropy from an object under test to elsewhere. If you only look at the object, and not the full system including the detector, it looks like the wavefunction of the object has collapsed.

 

[Khashishi]

In the cat analogy (and I know this is sounding funny as an analogy, but we know we can translate the example into something more realistic) what's the status of the cat?

This depends on the interpretation of quantum mechanics you ascribe to. If you believe in the many worlds interpretation, then in some worlds the cat is alive and in other worlds the cat is dead. If you believe in collapse, then it depends on what causes a collapse.

You can treat the poison apparatus as a detector which measures the state of an atom. By measuring the atom, it is taking the entropy of the atom state and moving it into something else. If the poison apparatus uses electricity, then the apparatus will give off heat. The cat also uses energy and gives off heat. Heat is disordered energy which removes excess entropy from macroscopic objects like cats. So, there's no need to put the cat in a mixture of dead and alive (which is a very, very high entropy state) since it only needs to give off a moderate amount of entropy to fully detect the state of the poison.

For macroscopic objects (objects large enough to give off heat), they are always in some mixed state, but we can't easily control which mixed state like we can with an atom. It is "easier" for a cat to be alive or dead and giving off heat than for the cat to be in a mix of alive and dead. I don't really know why.

 

[Nugatory]

Y
In the cat analogy (and I know this is sounding funny as an analogy, but we know we can translate the example into something more realistic) what's the status of the cat? It surely knows if it's alive, even if before we open the box we don't know. This to me means the example, and the issue in general is NOT about observation or measurement. I.e. whether or not we're able to observe the cat by lifting the lid has nothing to do with the state of the cat itself. So why does everyone seem to think it does?

Everyone doesn't. When Schrodinger introduced his thought experiment he was not seriously suggesting that the cat would end up in a superposition of dead and alive. He was pointing out that the then-current understanding of the mathematical formalism of QM didn't explain why the cat didn't end up in such a state; this unreasonable result suggested that something was wrong with that understanding. It took a few decades to resolve this problem, and during that time the simultaneously dead/alive cat leaked into the popular imagination as a sort of urban legend. This makes

David Lindley's "Where does the weirdness go" is a good layman-friendly book on the modern understanding of the cat, which includes a called "quantum decoherence".

Why the fancy talk about "superposition" and the cat being dead or alive (or the electron having this or that specific location). Like I said, it seems somebody is projecting something about our ability to observe onto the nature of the universe.

Because of quantum decoherence measuring a single subatomic particle like an electron is interestingly different than measuring a cat, which consists of maybe $10^{25}$ particles; it's sort of like comparing a single gas molecule to the atmosphere of the earth. Thus, the cat is not a good starting place for trying to visualize how superposition works with subatomic particles and you shouldn't be surprised that applying the concept to the cat leads to silly results.

However, superposition is an essential part of the mathematical formalism of quantum mechanics, and that formalism describes the behavior of subatomic particles better than anything else we've found. That's why the fancy talk - it's an accurate description of the subatomic world.

 

[Fra]

A deeper IMO useful conceptual way to understand how this can make sense - which is i should state clearly is interpretation dependent as well - and thus a away to give it a kind o epistemological ontologty, is to first realist that there is bound to a MUTUAL influence between a system and its evironment. (action and reaction if you so wish).

=> In classical mechanics of GR there is a mutual influence between a particle andg geometry: Geometry "guides the particles" or tells the particle where to move, but the particle also unavoidably is part of determining that very geometry, how much depends on its mass. Einstein understood this, and struggled for some time to find howto describe this matematically.

In an inferential or "measurement theory" one can consider physical interactions as interactions between self-preserving information processing agents breeding in an a prior unknow environment. From this picture its clear that if your entire environment has a certain EXPECTATION on you, this will FORM you in a way that has nothing
to do with what is true or not. In fact the notion of absolute facts loose operational meaning, as everyone, even a presumed judge, bases his beliefs only upon existing information. Unfortunately this is NOT how QM as we know is constructed, but this "interpretation" still works! and i find it also to be the only reasonable one. (But one can argue that QM should be reconstructed, to give regular QM as a limiting case, and in its reformulation solve other open issues in physics such as unification and QG, but that's a differetn thread)

So for this reason, the information of the CAT encoded in the environment of the CAT are not indepdendent of the CAT itself, and vice versa. The CAT has been forged into superposition by its environment and the only way to break it, is to interact. And if the environment is "classical" then once information is in classical domain its kind of "public information" so whatever the classical points "knows", the human knows. So the HUMAN itself, or its brain has absolutely nothing todo with this. I am always disturbed when people start to talk about "mental images". Its ok to talk about it in a metaphorical sense, unless you take it literally and apply it to humans exclusively.

The decoherence approach is a technical perspective related to this, but its easy to get lost in technicalities. Confused technicalities can always be worked out, as its usually "complex" but not mind boggling, but its worse if you get confused with the conceptual understanding. This is why its still of value to find yourself a working interpretation, at least if you aspired for a deeper understanding of next level of theoretical physics!

/Fredrik

 

[nnope]

= From this picture its clear that if your entire environment has a certain EXPECTATION on you, this will FORM you in a way that has nothing
to do with what is true or not.
/Fredrik

That makes no sense, are you saying that the environment's expectation of me is what forms me? So if the environment expected me to be a black and white spotted Asian man that's what I would be?

 

[Fra]

That makes no sense, are you saying that the environment's expectation of me is what forms me? So if the environment expected me to be a black and white spotted Asian man that's what I would be?

Yes that's what I'm saying, but in order to not misinterpret, in the most general case this should be understood as an evolutionary process where both matter/observers and spacetime evolves together. Also when i write "you" i meant the physical system that is the observer.

I just realized that it may be hard to explain and motivate my arguments without peaking into the other can of worms:

What I am suggesting is that the environment limts what kind of subsystems that can be stable in long term. You can always throw a whale into the jungle, or you can throw an ice crytal into the sun, but it will not last long there.

So the forming process i talk about, is a deep way in how the particle zoo AND the laws for their interactions, evolve together. This is my core insight i was proposing, and it can be interpreted as observer - observer interactions. But formally this is just an interpretation at this point. The mature mathematics or algorithms needed to describe this interaction process is yet to be written.

I think the apparently strange conclusions here originate not from my interpretation but from strange premises in the question given. One usually takes examples, such as a CAT insted of an electron, just so that the conclusion should seem faulty. But let's realize how hard not to say practically impossible it would be to construct a real cat in a quantum mechanical superposition? It is not theoretically impossible, but practically impossible. So no wonder the conclusion does not comply to common sense. But note that the premise is not common in the first place.

IF you want a conceptual analogy for humans, consider how even classical rumours and reputation on the stock market, that are widely spread creates an stable illusion of value, indistiguishable from the real thing. Similarly, rumours can decrease value by same mechanism. But similarly the bigger "lie" you try to market, the less likely is it to survive.

IF you want everyday examples that give insights to this "thinking", better than picturing cats in the box, is to look at rational player game theory and economic and social interactions. They are full of these things! Now try to understand how that works - shave off the irrelevant parts and take the abstraction - then apply it to physics, and this is where my interpretation stands. The big difference is that traditional thinking in physics is that particle zoo and laws are immutable. This is NOT how things work in social of ecnomical systes. The laws and the plays are subject to evolution and negotiation. And just like smoling also argued in his evolution of law - this must be the case also for the most fundamental laws we know of, the laws of physics. They are not mathematical eternal truth, as that attitude seems untenable. For arguments for THAT check out Time reborn.

So does mean i mean electrons do probabilistic estimates? No - particles don't to calculus and stuff liek that, instead there "computation" is simply in my view shifting and morphing its of its own microstructure. This is why "computational power" is reduces as we reach unification scale, and why the interactions rules are necessarily simpler.

So in summary, this is an "interpration" but which implicitly has a ambition of reconstruction of QM in mind. In sensse i suppose other interpretations like Bohmian mechanics also hides such an ambition. And interestingly there is a conection point i see between the information coded in the internal structrure and what Demystifiers calls "solipsist HV". In a way, this idea and Bohmian mechanics are on first sight as perpendicular as you can possible imagine, this is why i really find this worth mentioning again.
See https://www.physicsforums.com/threa...e-orthodox-quantum-mechanics-comments.924068/
and https://arxiv.org/abs/1112.2034

/Fredrik

 

[nnope]

Yes that's what I'm saying, but in order to not misinterpret, in the most general case this should be understood as an evolutionary process where both matter/observers and spacetime evolves together. Also when i write "you" i meant the physical system that is the observer.

I just realized that it may be hard to explain and motivate my arguments without peaking into the other can of worms:

What I am suggesting is that the environment limts what kind of subsystems that can be stable in long term. You can always throw a whale into the jungle, or you can throw an ice crytal into the sun, but it will not last long there.

So the forming process i talk about, is a deep way in how the particle zoo AND the laws for their interactions, evolve together. This is my core insight i was proposing, and it can be interpreted as observer - observer interactions. But formally this is just an interpretation at this point. The mature mathematics or algorithms needed to describe this interaction process is yet to be written.

I think the apparently strange conclusions here originate not from my interpretation but from strange premises in the question given. One usually takes examples, such as a CAT insted of an electron, just so that the conclusion should seem faulty. But let's realize how hard not to say practically impossible it would be to construct a real cat in a quantum mechanical superposition? It is not theoretically impossible, but practically impossible. So no wonder the conclusion does not comply to common sense. But note that the premise is not common in the first place.

IF you want a conceptual analogy for humans, consider how even classical rumours and reputation on the stock market, that are widely spread creates an stable illusion of value, indistiguishable from the real thing. Similarly, rumours can decrease value by same mechanism. But similarly the bigger "lie" you try to market, the less likely is it to survive.

IF you want everyday examples that give insights to this "thinking", better than picturing cats in the box, is to look at rational player game theory and economic and social interactions. They are full of these things! Now try to understand how that works - shave off the irrelevant parts and take the abstraction - then apply it to physics, and this is where my interpretation stands. The big difference is that traditional thinking in physics is that particle zoo and laws are immutable. This is NOT how things work in social of ecnomical systes. The laws and the plays are subject to evolution and negotiation. And just like smoling also argued in his evolution of law - this must be the case also for the most fundamental laws we know of, the laws of physics. They are not mathematical eternal truth, as that attitude seems untenable. For arguments for THAT check out Time reborn.

So does mean i mean electrons do probabilistic estimates? No - particles don't to calculus and stuff liek that, instead there "computation" is simply in my view shifting and morphing its of its own microstructure. This is why "computational power" is reduces as we reach unification scale, and why the interactions rules are necessarily simpler.

So in summary, this is an "interpration" but which implicitly has a ambition of reconstruction of QM in mind. In sensse i suppose other interpretations like Bohmian mechanics also hides such an ambition. And interestingly there is a conection point i see between the information coded in the internal structrure and what Demystifiers calls "solipsist HV". In a way, this idea and Bohmian mechanics are on first sight as perpendicular as you can possible imagine, this is why i really find this worth mentioning again.
See https://www.physicsforums.com/threa...e-orthodox-quantum-mechanics-comments.924068/
and https://arxiv.org/abs/1112.2034

/Fredrik

So this an interpretation you have developed? What is it that makes an expectation? How is there an expectation in the absence of life? Sounds like natural selection for QM?

 

[Fra]

How is there an expectation in the absence of life? Sounds like natural selection for QM?

Yes you can say that. Its a kind of natural selection for fundamental physical interactions. But mixed with some conjectures. But the formalism is not yet fully worked out which us why all i can claim atm is an interpretation.

An expectation is implicit in the coded microstructure in the sense that the "computation" or the observers "rational choices" about howto act against the noisy environment is pictuted as a random process. The key is that what is random and what is not is observerdependent. So what is a random process from the point of view of the imside obsever is seen as anything but random from the outside.

/Fredrik

 

[nnope]

Yes you can say that. Its a kind of natural selection for fundamental physical interactions. But mixed with some conjectures. But the formalism is not yet fully worked out which us why all i can claim atm is an interpretation.

An expectation is implicit in the coded microstructure in the sense that the "computation" or the observers "rational choices" about howto act against the noisy environment is pictuted as a random process. The key is that what is random and what is not is observerdependent. So what is a random process from the point of view of the imside obsever is seen as anything but random from the outside.

/Fredrik

So basically the observer that's causing the expectation or 'selection process' is sonething random. This doesn't require a consciousness observer. But how do you explain the lack of artefacts from previous random manifestations?

 

[Fra]

We are starting to get off topic here but to comment shortly.

So basically the observer that's causing the expectation or 'selection process' is sonething random. This doesn't require a consciousness observer. But how do you explain the lack of artefacts from previous random manifestations?

Not sure what you mean? which artefacts?

What i envision as random walks is time evolution. But its not a memoryless randommness like markov chains, the observers microstructure coded a memory of histtory, and time evolution follows from randomness guided by a non-random prior structure. So an arrow of time is implicit in this structure as well.

/Fredrik

 

[Lord Jestocost]

When Schrodinger introduced his thought experiment he was not seriously suggesting that the cat would end up in a superposition of dead and alive. He was pointing out that the then-current understanding of the mathematical formalism of QM didn't explain why the cat didn't end up in such a state; this unreasonable result suggested that something was wrong with that understanding. It took a few decades to resolve this problem, and during that time the simultaneously dead/alive cat leaked into the popular imagination as a sort of urban legend. This makes

David Lindley's "Where does the weirdness go" is a good layman-friendly book on the modern understanding of the cat, which includes a called "quantum decoherence".

“Decoherence” doesn’t convert a superposition state into a proper mixed state. A superposition state remains a superposition state in course of time, even in case it is “decohered” as heavy as possible. What one seems to get by means of decoherence in course of time is sometimes labeled an “improper mixed state” (maybe, that's the reason for all that confusion), but this label merely obscures that it is still a pure superposition state.

Consider a superposition and its evolution in course of time according to the appropriate time dependent Schroedinger equation. There is no physical process - how irreversible it might be - which is capable to reduce interference terms exactly to zero**. The whole information which the observer had at the beginning of the measuring process remains physically unchanged during the measuring act, that's what follows from quantum theory. Thus, no increase in entropy takes place and, consequently, no conversion of a pure state into a mixed state can take place. Quantum theory doesn't allow in such cases definite outcomes to be realized, whereas at the level of our human consciousness it seems a matter of direct experience that such outcomes occur. Quantum theory is straightforward, what’s hard to understand is classical physics. And trying to think about quantum phenomena in terms of classical notions and conception leads always to fundamental confusion.

Does anyone really believe that Schroedinger wasn’t aware of the decoherence stuff. Schroedinger wanted exactly to point out with his cat fable - a little bit ironically – that no unitary treatment of the time dependence can explain why only one of the dynamically independent components is finally experienced: "There is a difference between a 'shaky or out-of-focus photograph' and a 'snapshot of clouds and fog banks'." When the quantum mechanical formalism is consequently applied, the quantum ignorance “where the desired information simply doesn’t exist” (snapshot of clouds and fog banks) cannot be replaced by the classical ignorance “where the desired information exists but is hidden” (shaky or out-of-focus photograph). The conceptual transition from quantum to classical ignorance – from potentiality to actuality - has to be put in “by hand”. To say that - at the moment when you open the box - you will observe the “cat” to be either “dead” or “alive” or “bloody furious”, is nothing but utterly trivial; but quantum theory cannot tell you how a single potentiality (the desired information simply doesn’t exist) becomes either this or that actuality.

The forum is entitled: „Physics Forums - The Fusion of Science and Community“. The honest answer to all these questions regarding the quantum enigma and the meaning of observations is that given by @StevieTNZ in comment#4: “We have no solution to the measurement problem for standard quantum mechanics (versus Bohmian Mechanics), so anything that deals with answering about observations to make a potentiality become an actuality (e.g. from superposition of states to one state) is, at this time, a guess.” Thus, to my mind, the community can expect that questions are answered on the base of physics (and not on the base of "interpretational preferences“ which some respondents adhere to regarding quantum theory).

** “Let us go back however to less elevated questions. I did not yet mention that decoherence is a dynamical effect that is never perfectly exact. Entangled states of a measured quantum object and a measuring device are disentangled, but a tiny amount of entanglement (or superposition) always survives. The probability for observing a macroscopic interference effect between a dead and a live cat is never exactly zero, but extremely small and becoming exponentially smaller with larger values of time.” (Roland Omnes, in “Decoherence And Ontology“, Ontology Studies 8, 2008 55)

 

[anothergol]

This depends on the interpretation of quantum mechanics you ascribe to. If you believe in the many worlds interpretation, then in some worlds the cat is alive and in other worlds the cat is dead. If you believe in collapse, then it depends on what causes a collapse.

Why is the many worlds interpretation a lesser adopted/liked one btw?
I mean, ok, seems like that interpretation is vague, but it looks like it's disliked enough for most not to bother going deeper. While to me, it sounds like the simplest theory. I read about the others, and most seem to try to get rid of the "other possibilities" as soon as possible. But I don't understand the problem of having, and keeping an infinity of parallel universes.