Question relating to Schrodinger's Cat

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Question relating to Schrodinger's Cat

#1  Postby Panderos » Jan 27, 2011 7:13 pm

Ok so, until I look in the box, the cat might be in the alive state, it might be in the dead state, or it might be in the superposition of dead and alive states.

Then I look and the wavefunction collapses and it will be either dead or alive.

But that implies theres something special about humans. That we have the power to make it so just by observing. But I've also heard, in reference to quantum computing, that 'even a passing electron can 'look' and collapse the wavefunction' of some delicate system. I think I've heard this anyway.

So surely, if electrons can do it, then a passing electron in the cat box will make the wavefunction collapse and I'll have nothing to do with it. So whats the answer?

Thanks.
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Re: Question relating to Schrodinger's Cat

#2  Postby Thommo » Jan 27, 2011 7:22 pm

The cat is a thought experiment, it wouldn't work in reality, because as you say information would leak out of the box in the form of heat, light, electrons etc. so the superposition wouldn't be preserved.

QM observation doesn't make any distinction between a human observer an animal or even a single photon.
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Re: Question relating to Schrodinger's Cat

#3  Postby Darkchilde » Feb 02, 2011 9:29 am

The cat will be in a superposition of states until the box is opened. This thought experiment was a way by Schroedinger to show his malcontent with the Copenhagen interpretation of QM. However the thought experiment has remained as a way to explain the Copenhagen interpretation.

Now, the major point of the Copenhagen interpretation is measurement. What measurement is, is not defined in this interpretation, and could be anything from a simple observer (like a photon) to measuring equipment. In another thread, I had posted a concise summary of the Copenhagen interpretation, which I am repeating here:

The Copenhagen interpretation was put forth by people like Niels Bohr, Werner Heisenberg, etc. and it is the mainstream one, if I could call it that. It has been named the Copenhagen interpretation because of the location of its main proponents, like Niels Bohr between 1924 and 1927. In the Copenhagen interpretation, the wavefunction describes the state of a quantum system. The solutions to the Schrodinger equation for a specific quantum system are all wavefunctions, and each describes one of the probable states of the quantum system. Each wavefunction has a probability associated with it; until we measure one of the observables (measurable properties of a quantum system), the system does not have any quantum state associated with it. When we take a measurement, the system “decides” its quantum state, and the solution of the Schrodinger equation collapses to the specific wavefunction associated with the measurement. According to the Copenhagen interpretation, only the measurement of observables has any meaning, and this measurement “decides” the state of the quantum system.
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Re: Question relating to Schrodinger's Cat

#4  Postby twistor59 » Feb 02, 2011 11:44 am

Darkchilde wrote:The cat will be in a superposition of states until the box is opened. This thought experiment was a way by Schroedinger to show his malcontent with the Copenhagen interpretation of QM. However the thought experiment has remained as a way to explain the Copenhagen interpretation.

Now, the major point of the Copenhagen interpretation is measurement. What measurement is, is not defined in this interpretation, and could be anything from a simple observer (like a photon) to measuring equipment. In another thread, I had posted a concise summary of the Copenhagen interpretation, which I am repeating here:

The Copenhagen interpretation was put forth by people like Niels Bohr, Werner Heisenberg, etc. and it is the mainstream one, if I could call it that. It has been named the Copenhagen interpretation because of the location of its main proponents, like Niels Bohr between 1924 and 1927. In the Copenhagen interpretation, the wavefunction describes the state of a quantum system. The solutions to the Schrodinger equation for a specific quantum system are all wavefunctions, and each describes one of the probable states of the quantum system. Each wavefunction has a probability associated with it; until we measure one of the observables (measurable properties of a quantum system), the system does not have any quantum state associated with it.


Not quite. The system does still have a quantum state, as described by the wavefunction. It's just that, until the act of measurement, this state may not be an eigenstate of the operator representing the variable you're about to measure. So the variable doesn't "have" a definite value.

Darkchilde wrote:
When we take a measurement, the system “decides” its quantum state, and the solution of the Schrodinger equation collapses to the specific wavefunction associated with the measurement. According to the Copenhagen interpretation, only the measurement of observables has any meaning, and this measurement “decides” the state of the quantum system.


Yes, immediately after the measurement the system is in an appropriate eigenstate. The choice of this eignestate is where the randomness comes in.
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Re: Question relating to Schrodinger's Cat

#5  Postby Rilx » Feb 02, 2011 11:55 am

"Observation" means that the observer detects the observed by "touching" it with some system which changes its energy state. If the observed itself radiates some detectable energy, you don't need to "touch" it, but the radiation itself changes it's energy state.

Thought experiments have their pitfalls, always.
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Re: Question relating to Schrodinger's Cat

#6  Postby Darkchilde » Feb 02, 2011 12:06 pm

Rilx wrote:"Observation" means that the observer detects the observed by "touching" it with some system which changes its energy state. If the observed itself radiates some detectable energy, you don't need to "touch" it, but the radiation itself changes it's energy state.

Thought experiments have their pitfalls, always.


No, until a measurement is performed, according to the Copenhagen interpretation, we do not know to which probability the wavefunction will collapse to. There is no meaning in saying that the energy state will change, because we may not know what that state is accurately, as we have the Heisenberg Uncertainty Principle and one of the pairs of variables is energy/time.

So, we may measure the energy of a quantum system accurately, but we will not know when that measurement applies to!

As I said, the Copenhagen interpretation talks about measurement, but it does not define what that measurement is. There is no definite energy or other state associated with a quantum system, only probabilities, until the measurement is performed.

Twistor, other than energy/time and position/momentum, are there any other pairs of variables that we cannot measure both accurately, as per the Heisenberg Uncertainty Principle?
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Re: Question relating to Schrodinger's Cat

#7  Postby Rilx » Feb 02, 2011 12:30 pm

You are right concerning the CI, Darkchilde, but my post was addressed to OP. "Observation" is prone to confuse people to think that it (especially human "seeing") doesn't have any physical effect to the observed.

But that implies theres something special about humans. That we have the power to make it so just by observing.
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Re: Question relating to Schrodinger's Cat

#8  Postby twistor59 » Feb 02, 2011 12:38 pm

Rilx wrote:You are right concerning the CI, Darkchilde, but my post was addressed to OP. "Observation" is prone to confuse people to think that it (especially human "seeing") doesn't have any physical effect to the observed.

But that implies theres something special about humans. That we have the power to make it so just by observing.


Absolutely, the measurement process is described by an interaction Hamiltonian, so there is a physical effect on the system being observed.
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Re: Question relating to Schrodinger's Cat

#9  Postby eric8476 » Sep 11, 2011 11:32 pm

isn't the entire thought experiment flawed? the variable is the decaying matter, it either decays or not then therefore the cat would be dead or alive, not in limbo.
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Re: Question relating to Schrodinger's Cat

#10  Postby hackenslash » Sep 12, 2011 12:09 am

Let's try a slightly different approach:

First, it's important to outline the precise details of the thought experiment, because that's where the devil resides.

In the experiment, the cat is placed in a box with a vial of poison, which is triggered to release by the decay of a single atom of some suitably radioactive element. Now, the exact moment of decay is an entirely statistically independent event, which cannot be predicted with any accuracy. It may decay as soon as you close the box, or it may not decay for millions of years. Indeed, only when you have sufficient atoms of said element for the law of large numbers to appply can you make any sort of prediction, and that will be a probabilistic one. To simplify this concept, if you have two atoms, then the half-life predicts that one of them will decay in x amount of time, but you can't predict which of the two atoms or when in that time the decay will occur. This is very much an oversimplification, and in reality, it requires far greater numbers of atoms to present enough for statistical applications to have any predictive value.

Under the Copenhagen interpretation, the atom exists in both the decayed and un-decayed states simultaneously, and observations collapses the wavefunction, defining the eigenstate of the atom. Thus, in the thought experiment, the cat is both alive and dead at the same time, because the atom is both decayed and un-decayed, and therefore the poison is both released and unreleased at the same time.

Panderos wrote:Ok so, until I look in the box, the cat might be in the alive state, it might be in the dead state, or it might be in the superposition of dead and alive states.


No. It's always in a superposition of both alive and dead. The reason for this is that the poison is both released and unreleased at the same time.

Then I look and the wavefunction collapses and it will be either dead or alive.


Yep.

But that implies theres something special about humans. That we have the power to make it so just by observing. But I've also heard, in reference to quantum computing, that 'even a passing electron can 'look' and collapse the wavefunction' of some delicate system. I think I've heard this anyway.


Well, this is the nub of the misunderstanding. Anything can constitute an observer, including an electron, a photon, or whatever. In no way does an observer have to be conscious to collapse the wavefunction.

So surely, if electrons can do it, then a passing electron in the cat box will make the wavefunction collapse and I'll have nothing to do with it. So whats the answer?


Well, Darkchilde has given the answer, namely that this thought experiment was erected by Schrödinger to argue against the Copenhagen interpretation, and shouldn't be thought of beyond that. It's somewhat unfortunate that this is employed as an analogy for what actually occurs for this reason. The problem is that it's such a beautiful analogy, and it works.

In reality, the probability of a cat existing in a state of superposition is so extremely low that it has been calculated that it would take longer than the existence of the universe (past and future) before such an event is likely to occur. However, thinking that this means it can't happen commits several fallacies, one of which is elucidated by Cali's exposition of the serial trials fallacy, but can be taken further. What the serial trials fallacy, as demonstrated in Cali's wonderful treatise, doesn't actually tell you is that, even in the presence of a small number of participants, even the most improbable events can happen first time out of the gate, and indeed even in the presence of one try. It may look from his essay that it requires many participants to be involved in order to achieve the goal on the first attempt, but that isn't true, and to assume it is is to commit a different, but related fallacy, namely the gambler's fallacy.

There are no barriers, probabilistically speaking, to a cat existing in a state of superposition. It's extremely unlikely, not least because every particle that comprises the cat constitutes an observer capable of collapsing the wavefunction, but it isn't impossible.

Darkchilde wrote:Twistor, other than energy/time and position/momentum, are there any other pairs of variables that we cannot measure both accurately, as per the Heisenberg Uncertainty Principle?


Field value/rate of change (which are really just expression of position/momentum).

Eric8476 wrote:isn't the entire thought experiment flawed? the variable is the decaying matter, it either decays or not then therefore the cat would be dead or alive, not in limbo.


It isn't in limbo, it's actually both alive and dead. In any event, I've covered this above. It's a thought experiment, and really only analogises the principle of quantum superposition. The decaying atom most definitely can exist in a state of superposition, and this has been experimentally verified. Indeed, the computer you are posting from employs a variation of superposition, in the form of quantum tunnelling, for its operation.
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Re: Question relating to Schrodinger's Cat

#11  Postby eric8476 » Sep 12, 2011 12:29 am

hackenslash wrote:Under the Copenhagen interpretation, the atom exists in both the decayed and un-decayed states simultaneously, and observations collapses the wavefunction, defining the eigenstate of the atom. Thus, in the thought experiment, the cat is both alive and dead at the same time, because the atom is both decayed and un-decayed, and therefore the poison is both released and unreleased at the same time.


hackenslash wrote:It isn't in limbo, it's actually both alive and dead. In any event, I've covered this above. It's a thought experiment, and really only analogises the principle of quantum superposition. The decaying atom most definitely can exist in a state of superposition, and this has been experimentally verified. Indeed, the computer you are posting from employs a variation of superposition, in the form of quantum tunnelling, for its operation.


if the decaying matter can be both decayed and undecayed then schrodinger disproves quantum mechanics. his linear approach is not consistant with measuring waves, am i right?

isn't it how to measure wavefunction that collapses the wavefunction, not obsevations?

the geiger measuring instrument for detecting decay would detect the matter's decayed position in time if the decaying matter is both decayed and not decayed, that would render that cat dead.

if we can observe without collapsing the wavefunction then we would not have any problems. we don't have the technology to observe these things. if we do have the technology then the copenhagen interpretation would be obsolite.
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Re: Question relating to Schrodinger's Cat

#12  Postby hackenslash » Sep 12, 2011 5:22 am

eric8476 wrote:if the decaying matter can be both decayed and undecayed then schrodinger disproves quantum mechanics.


Really? You might want to have a word with your computer about that.

his linear approach is not consistant with measuring waves, am i right?


No. Indeed the function we use for these waves is the Schrödinger equation, also known as the Schrödinger wave equation.

isn't it how to measure wavefunction that collapses the wavefunction, not obsevations?


Huh? That doesn't parse correctly in English. If it's what I think you're trying to say, then no. It's observation that collapses the wavefunction, but you have to be careful how you define 'observe' and 'observer', because those terms don't necessarily mean what you think they mean.

the geiger measuring instrument for detecting decay would detect the matter's decayed position in time if the decaying matter is both decayed and not decayed, that would render that cat dead.


Indeed. That would constitute an observation of the system, thereby collapsing the wavefunction.

if we can observe without collapsing the wavefunction then we would not have any problems.


Well, observation is collapse of the wavefunction, and we don't actually have a problem.

we don't have the technology to observe these things. if we do have the technology then the copenhagen interpretation would be obsolite.


No, because this is nothing to do with technology. We can't possess the technology to observe without collapsing the wavefunction, because observation and collapse are one and the same. There exists no such technology.
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Re: Question relating to Schrodinger's Cat

#13  Postby lucek » Sep 12, 2011 6:37 am

OK first I'm going to echo the others. Schrodinger's Cat is actually a straw man that has sense been adopted to describe effects inconceivable to most 100 level physics students. Others like this include the big bang, the lader of evolution etc.

Now there is a grain of truth to it. An object that would be an observer can in fact be in a superposition. An experiment took a macroscopic rotor applied an QM object in to it that was currently in a superposition, and the rotor went into a superposition of vibrating/not vibrating. However in order to increase the chance of this working it was lowered in temperature to almost absolute 0 to reduce noise.
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Re: Question relating to Schrodinger's Cat

#14  Postby eric8476 » Sep 12, 2011 6:55 am

hackenslash wrote:Really? You might want to have a word with your computer about that.


computers use 1 and 0? schrodinger's thought experiment uses the variable of the decaying matter. the cat's status is the result not the variable. copenhagen states that the matter can be decaying and not at the same time then the conclusions of schrodinger is disproving this statement. how is this not debunking?

hackenslash wrote:No. Indeed the function we use for these waves is the Schrödinger equation, also known as the Schrödinger wave equation.


is it the only equation used to measure the wavefunction?

hackenslash wrote:Huh? That doesn't parse correctly in English. If it's what I think you're trying to say, then no. It's observation that collapses the wavefunction, but you have to be careful how you define 'observe' and 'observer', because those terms don't necessarily mean what you think they mean.


measuring and observing are different things. we don't have the technology to observe particles in areas as of yet without collapsing the wavefunction

hackenslash wrote:Indeed. That would constitute an observation of the system, thereby collapsing the wavefunction.


that is a result, observation or not. check this link here: http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics and scroll down the the conclusion area, there is a chart that shows different interpretations and some do not suggest collapsing of the wavefunction?

hackenslash wrote:Well, observation is collapse of the wavefunction, and we don't actually have a problem.

take the quantum state measuring electrons that are around a nucleus, for instance. with advanced technology, the electrons can be observed in the electron cloud of the atom. thus the wavefunction collapsing or not would be a moot point.

hackenslash wrote:No, because this is nothing to do with technology. We can't possess the technology to observe without collapsing the wavefunction, because observation and collapse are one and the same. There exists no such technology.


we can possess the advanced technology for observing without collapsing the wavefunction. it is possible. it doesn't exist yet, but it can exist. our grandchildren could be using them and not us but it's possible none the less.

lucek wrote:OK first I'm going to echo the others. Schrodinger's Cat is actually a straw man that has sense been adopted to describe effects inconceivable to most 100 level physics students. Others like this include the big bang, the lader of evolution etc.


is it to separate classical mechanics from quantum mechanics concepts (like wave-particle duality)?
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Re: Question relating to Schrodinger's Cat

#15  Postby twistor59 » Sep 12, 2011 7:42 am

eric8476 wrote:
hackenslash wrote:Really? You might want to have a word with your computer about that.


computers use 1 and 0? schrodinger's thought experiment uses the variable of the decaying matter. the cat's status is the result not the variable. copenhagen states that the matter can be decaying and not at the same time then the conclusions of schrodinger is disproving this statement. how is this not debunking?

[/quote]

By "conclusions of schrodinger", you presumably mean Schroedinger's cat experiment, not the conclusions of Schroedinger himself. If so, then I wouldn't say "disproving", but rather "highlighting a problem with":

The atom is in a quantum superposition (decayed+not decayed). There would then be a long causal chain of interactions leading to the eventual state of the cat. The atom in the gamma ray detector would be in a superpostion of detected+not detected. The electric current would be in a superposition of generated+not generated. The motor would be in a superposition of in motion + not in motion etc. All the time along the chain the items are getting bigger -- less microscopic and more macroscopic.

We know that we never see cats in a superposition of states. The question is therefore - "where along the causal chain do the rules of quantum mechanics break down and superposition gets lost" ?. This is the "Measurement Problem".

There have been many proposed answers to this over the years, and if you want an animated physics coffee table discussion, this is one topic guaranteed to bring it about.
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Re: Question relating to Schrodinger's Cat

#16  Postby hackenslash » Sep 12, 2011 5:18 pm

eric8476 wrote:computers use 1 and 0?


Computers, or more specifically the semiconductors in computers, employ devices known as Esaki diodes, which operate on the basis of quantum tunnelling. Of course, I already addressed this in the previous post of mine you quoted.

schrodinger's thought experiment uses the variable of the decaying matter. the cat's status is the result not the variable. copenhagen states that the matter can be decaying and not at the same time then the conclusions of schrodinger is disproving this statement. how is this not debunking?


I see that Twistor has covered this in more depth than I would have done.

is it the only equation used to measure the wavefunction?


It isn't used to measure the wavefunction, but to describe the probability amplitude of one of a pair of conjugate variables.

measuring and observing are different things.


Care to highlight the distinction, or to point out how one can measure something without observation?

we don't have the technology to observe particles in areas as of yet without collapsing the wavefunction


It isn't a matter of technology, and your continued reassertion that it is doesn't actually move us forward. Indeed, there's good reason to think that those conjugate variables don't actually possess any definite values until observed.

that is a result, observation or not.


What?

check this link here: http://en.wikipedia.org/wiki/Interpretations_of_quantum_mechanics and scroll down the the conclusion area, there is a chart that shows different interpretations and some do not suggest collapsing of the wavefunction?


I'm aware of them, thanks. There are problems with those that don't include the collapse of the wavefunction. Not insurmountable by any means, but suggestive of problems. For example, the Many-Worlds interpretation is horribly unparsimonious. Not that parsimony is indicative of veracity, but as a heuristic in hypothesis selection, it's proved extremely useful, so not to be dismissed lightly. the de Broglie-Bohm intepretation runs into difficulties with the observation of superposition (indeed, and as Darkchilde pointed out above, it has been observed in macroscopic objects), because superposition removes the need for the 'pilot-wave'.

I tend to favour the path integral formulation, but not with any huge conviction. Since they are pretty much inseperable in terms of prediction of observations, there's no reason to choose between them at this point, but those without wavefunction collapse are the easiest to lay aside until some unique predictions arise from one of them. The Copenhagen interpretation has brought us a very long way, and those hypotheses haven't actually brought us any further (apart from the path integral).

In any event, none of this supports your assertion that measurement and observation are different things.

take the quantum state measuring electrons that are around a nucleus, for instance. with advanced technology, the electrons can be observed in the electron cloud of the atom. thus the wavefunction collapsing or not would be a moot point.


They can certainly be observed, but they can only be observed with a given position or a given momentum, not both. The very best we can do is a kind of weak measurement that can give a vague average of both, to the tolerance of the wavelength of the photon used for observation, but accuracy is impossible, because the uncertainty principle cannot be violated with pairs of conjugate variables. The more accurately we know one, the less accurately we can know the other.

we can possess the advanced technology for observing without collapsing the wavefunction. it is possible. it doesn't exist yet, but it can exist. our grandchildren could be using them and not us but it's possible none the less.


And the evidence in support of this contention is...?

Since there is good reason to suppose that pairs of conjugate variables don't actually possess values until they are observed, I'd love to see how you're going to manage this.
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Re: Question relating to Schrodinger's Cat

#17  Postby Darkchilde » Sep 14, 2011 11:27 am

eric8476 wrote:
we can possess the advanced technology for observing without collapsing the wavefunction. it is possible. it doesn't exist yet, but it can exist. our grandchildren could be using them and not us but it's possible none the less.


There is a problem here. Once the wavefunction is observed, by anything, even by a photon or by an electron, or a device, then the wavefunction collapses to one of the associated probabilities. A device that observes that does not collapse the wavefunction, would be one that does not do any observation. The mere act of the device's observation is the one that will collapse the wavefunction.
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Re: Question relating to Schrodinger's Cat

#18  Postby cavarka9 » Sep 14, 2011 11:49 am

shoot the damn cat, all questions will go away on their own
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Re: Question relating to Schrodinger's Cat

#19  Postby zaybu » Sep 14, 2011 12:32 pm

There's one problem with these explanations: the wave function is NEVER observed. Observables in QM are operators, such as position, momentum, energy, spin. The wavefunction is just a mathematical tool that allows calculation of expectation values of these observables. Any other interpretation of the wavefunction is just pure speculation, unsupported by any evidence.
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Re: Question relating to Schrodinger's Cat

#20  Postby eric8476 » Sep 14, 2011 7:19 pm

twistor59 wrote:By "conclusions of schrodinger", you presumably mean Schroedinger's cat experiment, not the conclusions of Schroedinger himself. If so, then I wouldn't say "disproving", but rather "highlighting a problem with":

The atom is in a quantum superposition (decayed+not decayed). There would then be a long causal chain of interactions leading to the eventual state of the cat. The atom in the gamma ray detector would be in a superpostion of detected+not detected. The electric current would be in a superposition of generated+not generated. The motor would be in a superposition of in motion + not in motion etc. All the time along the chain the items are getting bigger -- less microscopic and more macroscopic.

We know that we never see cats in a superposition of states. The question is therefore - "where along the causal chain do the rules of quantum mechanics break down and superposition gets lost" ?. This is the "Measurement Problem".

There have been many proposed answers to this over the years, and if you want an animated physics coffee table discussion, this is one topic guaranteed to bring it about.


the activity of the atom does not put the other functions of the experiment in superposition. the gamma ray detector detects what is given. when of if the atom goes into superposition the point in time the atom demonstrates a decayed point would be detected or else the atom does not go into superposition (i.e. it is not both decayed or not decayed because it would not have demonstrated the decayed status).

hackenslash wrote:Computers, or more specifically the semiconductors in computers, employ devices known as Esaki diodes, which operate on the basis of quantum tunnelling. Of course, I already addressed this in the previous post of mine you quoted.


do the elctrons permiate through the barrior? do the electrons change their shape to slip past the solid barrior? whoever reads this make sure you credit me when you present your nobel prize presentation. hehehe

hackenslash wrote:I see that Twistor has covered this in more depth than I would have done.


get into it, come on, use the thought experiment to exercise your mind. :grin:

hackenslash wrote:It isn't used to measure the wavefunction, but to describe the probability amplitude of one of a pair of conjugate variables.


hhhhmmmm, thanks.

hackenslash wrote:Care to highlight the distinction, or to point out how one can measure something without observation?


a observation is when you look at a leaf falling from a tree. a measurement is calculating the velocity of the fall.

hackenslash wrote:It isn't a matter of technology, and your continued reassertion that it is doesn't actually move us forward. Indeed, there's good reason to think that those conjugate variables don't actually possess any definite values until observed.


do you think the electrons passing through a double slit know that they are being watched? or is the measuring device interfering with the electron flow.

is it a new form of functioning life? is it a new form of functioning conciousness? does it explain conciousness we have, like wondered about in another thread? that would explain why we are looking for a "God-particle". hehehe

this could also disprove a notion of a God with proving conciousness function.

hackenslash wrote:What?


the result is what happens at the conclusion of the experiment. it could be observable, measurable, both or neither, but it is a result none the less.

hackenslash wrote:I'm aware of them, thanks. There are problems with those that don't include the collapse of the wavefunction. Not insurmountable by any means, but suggestive of problems. For example, the Many-Worlds interpretation is horribly unparsimonious. Not that parsimony is indicative of veracity, but as a heuristic in hypothesis selection, it's proved extremely useful, so not to be dismissed lightly. the de Broglie-Bohm intepretation runs into difficulties with the observation of superposition (indeed, and as Darkchilde pointed out above, it has been observed in macroscopic objects), because superposition removes the need for the 'pilot-wave'.

I tend to favour the path integral formulation, but not with any huge conviction. Since they are pretty much inseperable in terms of prediction of observations, there's no reason to choose between them at this point, but those without wavefunction collapse are the easiest to lay aside until some unique predictions arise from one of them. The Copenhagen interpretation has brought us a very long way, and those hypotheses haven't actually brought us any further (apart from the path integral).

In any event, none of this supports your assertion that measurement and observation are different things.


i think quantum mechanics needs more ways of looking at things that can be calculated and/or proven. some of the ideas now are confined to speculation too much.

http://www.thefreedictionary.com/measurement - "3. The dimension, quantity, or capacity determined by measuring". factors not needed for observing.

http://dictionary.reference.com/browse/observation - it's noticing something.

hackenslash wrote:They can certainly be observed, but they can only be observed with a given position or a given momentum, not both. The very best we can do is a kind of weak measurement that can give a vague average of both, to the tolerance of the wavelength of the photon used for observation, but accuracy is impossible, because the uncertainty principle cannot be violated with pairs of conjugate variables. The more accurately we know one, the less accurately we can know the other.


yes, the more we know about a position, the less we know the momentum and vise versa. but if a measuring device can view and record the electron cloud space and the electrons in motion without stopping the electron, the momentum can be noted and the position can be noted after viewing the pausing of a recording.

hackenslash wrote:And the evidence in support of this contention is...?

Since there is good reason to suppose that pairs of conjugate variables don't actually possess values until they are observed, I'd love to see how you're going to manage this.


if you asked an educated person in the renaissance timeperiod about eluminating a place at night that person would not have an idea about the light bulb. catch my drift?

Darkchilde wrote:There is a problem here. Once the wavefunction is observed, by anything, even by a photon or by an electron, or a device, then the wavefunction collapses to one of the associated probabilities. A device that observes that does not collapse the wavefunction, would be one that does not do any observation. The mere act of the device's observation is the one that will collapse the wavefunction.


if there is superposition, a device could be programmed to factor in the different eigenstates and filter it or factor in the eigenstates or factor in the in between of eigenstates altogether.

are you saying the use of the particle that a wavefunction is for collapses the wavefunction?

zaybu wrote:There's one problem with these explanations: the wave function is NEVER observed. Observables in QM are operators, such as position, momentum, energy, spin. The wavefunction is just a mathematical tool that allows calculation of expectation values of these observables. Any other interpretation of the wavefunction is just pure speculation, unsupported by any evidence.


if a particle can be noticed without disturbing the superposition, collasping the wavefunction is not pertinent.
Last edited by eric8476 on Sep 14, 2011 9:27 pm, edited 6 times in total.
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