What do you think of this?:

http://physicsworld.com/cws/article/multimedia/2013/mar/07/is-schrodingers-cat-dead-or-alive

I thought that the current accepted thinking would recognise that not only is the cat an observer, the flask of poison is also an observer.

(I also thought that illustrating the absurdity of giving special status to human observations was the point that Schrodinger wanted to make, rather than arguing that the cat was “really” dead and alive at the same time).

http://en.wikipedia.org/wiki/Schr%C3%B6dinger’s_cat

Wikipedia confirms my second supposition, but not the first.

I still don’t see why a Geiger counter triggering an electrical switch does not constitute an “observation”.

The Rev Dodgson said:

http://en.wikipedia.org/wiki/Schr%C3%B6dinger’s_cat

Wikipedia confirms my second supposition, but not the first.

I still don’t see why a Geiger counter triggering an electrical switch does not constitute an “observation”.

The Geiger counter is included to provide the random element. I suppose without a better understanding of decay the nature of the observation is obscure. I expect there would also be a more elegant explanation on offer.

Riff-in-Thyme said:

The Rev Dodgson said:

http://en.wikipedia.org/wiki/Schr%C3%B6dinger’s_cat

Wikipedia confirms my second supposition, but not the first.

I still don’t see why a Geiger counter triggering an electrical switch does not constitute an “observation”.

The Geiger counter is included to provide the random element. I suppose without a better understanding of decay the nature of the observation is obscure. I expect there would also be a more elegant explanation on offer.

I’d say it was the radioactive material that was providing the random element. The Geiger counter creates an electrical signal when it detects that a decay event has occurred. I don’t understand why this doesn’t count as an “observation” (but I don’t understand a lot about QM).

I should probably read this:

http://www.eng.fsu.edu/~dommelen/quantum/style_a/index.html

If only because of the title:

“Quantum Mechanics for Engineers”

The Rev Dodgson said:

What do you think of this?:

http://physicsworld.com/cws/article/multimedia/2013/mar/07/is-schrodingers-cat-dead-or-alive

I thought that the current accepted thinking would recognise that not only is the cat an observer, the flask of poison is also an observer.

(I also thought that illustrating the absurdity of giving special status to human observations was the point that Schrodinger wanted to make, rather than arguing that the cat was “really” dead and alive at the same time).

As it is a thought experiment, why not ask the cat? does it think it is dead or alive?

bob(from black rock) said:

The Rev Dodgson said:

What do you think of this?:

http://physicsworld.com/cws/article/multimedia/2013/mar/07/is-schrodingers-cat-dead-or-alive

I thought that the current accepted thinking would recognise that not only is the cat an observer, the flask of poison is also an observer.

(I also thought that illustrating the absurdity of giving special status to human observations was the point that Schrodinger wanted to make, rather than arguing that the cat was “really” dead and alive at the same time).

As it is a thought experiment, why not ask the cat? does it think it is dead or alive?

Kingy said:

bob(from black rock) said:

The Rev Dodgson said:

What do you think of this?:

http://physicsworld.com/cws/article/multimedia/2013/mar/07/is-schrodingers-cat-dead-or-alive

I thought that the current accepted thinking would recognise that not only is the cat an observer, the flask of poison is also an observer.

(I also thought that illustrating the absurdity of giving special status to human observations was the point that Schrodinger wanted to make, rather than arguing that the cat was “really” dead and alive at the same time).

As it is a thought experiment, why not ask the cat? does it think it is dead or alive?

LOLZ

bob(from black rock) said:

The Rev Dodgson said:

What do you think of this?:

http://physicsworld.com/cws/article/multimedia/2013/mar/07/is-schrodingers-cat-dead-or-alive

I thought that the current accepted thinking would recognise that not only is the cat an observer, the flask of poison is also an observer.

(I also thought that illustrating the absurdity of giving special status to human observations was the point that Schrodinger wanted to make, rather than arguing that the cat was “really” dead and alive at the same time).

As it is a thought experiment, why not ask the cat? does it think it is dead or alive?

“What have you done to the cat?! It looks half dead!”

-Schrodinger’s wife.

The Rev Dodgson said:

What do you think of this?:

http://physicsworld.com/cws/article/multimedia/2013/mar/07/is-schrodingers-cat-dead-or-alive

Not much.

The Rev Dodgson said:

I thought that the current accepted thinking would recognise that not only is the cat an observer, the flask of poison is also an observer.

I think of the flask of poison as being the output indicator of the Geiger counter rather than as an “observer” in its own right.

The Rev Dodgson said:

(I also thought that illustrating the absurdity of giving special status to human observations was the point that Schrodinger wanted to make, rather than arguing that the cat was “really” dead and alive at the same time).

I think his point was that mixed states at the classical level seem absurd, but that the quantum formalism doesn’t seem to have a way of preventing them from occuring.

The Rev Dodgson said:

I still don’t see why a Geiger counter triggering an electrical switch does not constitute an “observation”.

It does. FWIW, many physicists prefer to use the term “measurement” rather than “observation”, since “observation” tends to imply some kind of conscious observer. OTOH, there are still some physicists that claim that consciousness is somehow required for wavefunction collapse, but they are certainly in the minority.

There is currently no definitive resolution of the measurement problem , which is why there are a variety of interpretations of quantum mechanics .

However, we can look at the Schrodinger’s Cat problem as a nested hierarchy of measurements. The scientist measures whether the cat is alive or dead; the cat measures whether the Geiger counter has clicked or not clicked; the Geiger counter measures whether the atom has decayed or not.

Each sub-system has its own wavefunction, so they don’t all need to collapse simultaneously. So until the atom is measured, it’s in a state of
(undecayed atom + decayed atom).

When the Geiger counter measures it, we now have the (Geiger counter + atom) system in a mixed state of
((undecayed atom + unclicked counter) + (decayed atom + clicked counter))

When the cat measures the output of the Geiger counter we have
((undecayed atom + unclicked counter + live cat) + (decayed atom + clicked counter + dead cat))

And when the scientist opens the box and looks at the cat we have
((undecayed atom + unclicked counter + live cat + scientist sees live cat) + (decayed atom + clicked counter + dead cat + scientist sees dead cat))

Et cetera.

Also see Wigner’s friend

The Rev Dodgson said:

What do you think of this?:

http://physicsworld.com/cws/article/multimedia/2013/mar/07/is-schrodingers-cat-dead-or-alive

I thought that the current accepted thinking would recognise that not only is the cat an observer, the flask of poison is also an observer.

(I also thought that illustrating the absurdity of giving special status to human observations was the point that Schrodinger wanted to make, rather than arguing that the cat was “really” dead and alive at the same time).

The Rev Dodgson said:

I still don’t see why a Geiger counter triggering an electrical switch does not constitute an “observation”.

I haven’t read the article, but the many-worlds interpretation provides the best explanation of Schrodinger’s cat. All this talk about what constitutes a measurement that collapses the wavefunction is meaningless in the many-worlds interpretation because there is no collapse of the wavefunction. The cat remains alive in one set of universes and dead in another set of universes, and these remain in quantum superposition in the multiverse. But in the multiverse, there is also a superposition of the observer: in one set of universes, the observer becomes quantum entangled with the live cat, and in the other set of universes, the observer becomes quantum entangled with the dead cat. The observer is the one who opens the box because while the cat is also an observer, the cat’s observations are irrelevant to the experimenter’s knowledge of whether the cat is dead or alive.

The many-worlds interpretation, in particular quantum decoherence, makes it clear what an observation is, and makes it clear that the questions put forward by the Schrodinger cat experiment represent an incorrect view of the nature of observations.

The point where the objectively true measurement occurs is the point where the microscopic becomes macroscopic – the detection of the radioactive decay by the Geiger-counter. But it isn’t until the experimenter opens the box that (s)he becomes aware of which possibility (s)he is entangled with.

PM 2Ring said:

There is currently no definitive resolution of the measurement problem

It is my view that quantum decoherence within the correct version of the many-worlds interpretation does resolve the measurement problem. The key point is to understand that the different classical states within the multiverse are orthogonal components of the universal quantum state. Orthogonal components do not interfere with each other, which is why the different classical states cannot observe each other. Interference occurs when two non-orthogonal components are combined, and it is within the microscopic realm that one has significantly non-orthogonal components. In the classical realm, the dimension of the multi-particle quantum state is so large that the probability of two randomly chosen quantum states differing significantly from orthogonality becomes negligible. This is why classical states are orthogonal.

KJW said:

The many-worlds interpretation, in particular quantum decoherence, makes it clear what an observation is, and makes it clear that the questions put forward by the Schrodinger cat experiment represent an incorrect view of the nature of observations.

Yes, but the many-worlds interpretation is not the only interpretation. I can think of three other interpretations that I prefer to it:
the Copenhagen interpretation, the Ensemble interpretation and the Transactional interpretation.

mollwollfumble said:

KJW said:

The many-worlds interpretation, in particular quantum decoherence, makes it clear what an observation is, and makes it clear that the questions put forward by the Schrodinger cat experiment represent an incorrect view of the nature of observations.

Yes, but the many-worlds interpretation is not the only interpretation. I can think of three other interpretations that I prefer to it:
the Copenhagen interpretation, the Ensemble interpretation and the Transactional interpretation.

If it is to be an interpretation fight, I will Sunday night Interpretation Fight YOU,,, to the death!!!!!

cue spanish guitar

mollwollfumble said:

Yes, but the many-worlds interpretation is not the only interpretation.

Of course it’s not the only interpretation. It (or at least some variant of it) is the most natural and complete interpretation.

mollwollfumble said:

I can think of three other interpretations that I prefer to it:
the Copenhagen interpretation, the Ensemble interpretation and the Transactional interpretation.

Why are these preferable? For example, doesn’t the transactional interpretation require new physics to explain wavefunction collapse?

I’m going to read this:

http://cds.cern.ch/record/142461/files/198009299.pdf Bertlemann’s Socks and the Nature of Reality

before discussing this further.

From http://en.wikipedia.org/wiki/Many-worlds_interpretation#Probability

A consequence of removing wavefunction collapse from the quantum formalism is that the Born rule requires derivation, since many-worlds claims to derive its interpretation from the formalism. Attempts have been made, by many-world advocates and others, over the years to derive the Born rule, rather than just conventionally assume it, so as to reproduce all the required statistical behaviour associated with quantum mechanics. There is no consensus on whether this has been successful.

Everett, Gleason and Hartle

Everett (1957) briefly derived the Born rule by showing that the Born rule was the only possible rule, and that its derivation was as justified as the procedure for defining probability in classical mechanics. Everett stopped doing research in theoretical physics shortly after obtaining his Ph.D., but his work on probability has been extended by a number of people. Andrew Gleason (1957) and James Hartle (1965) independently reproduced Everett’s work, known as Gleason’s theorem which was later extended.

De Witt and Graham

Bryce De Witt and his doctoral student R. Neill Graham later provided alternative (and longer) derivations to Everett’s derivation of the Born rule. They demonstrated that the norm of the worlds where the usual statistical rules of quantum theory broke down vanished, in the limit where the number of measurements went to infinity.

Deutsch et al.

An information-theoretic derivation of the Born rule from Everettarian assumptions, was produced by David Deutsch (1999) and refined by Wallace (2002–2009) and Saunders (2004). Deutsch’s derivation is a two-stage proof: first he shows that the number of orthonormal Everett-worlds after a branching is proportional to the conventional probability density. Then he uses game theory to show that these are all equally likely to be observed. The last step in particular has been criticised for circularity. Some other reviews have been positive, although the status of these arguments remains highly controversial; some theoretical physicists have taken them as supporting the case for parallel universes. In the New Scientist article, reviewing their presentation at a September 2007 conference, Andy Albrecht, a physicist at the University of California at Davis, is quoted as saying “This work will go down as one of the most important developments in the history of science.”

Wojciech H. Zurek (2005) has produced a derivation of the Born rule, where decoherence has replaced Deutsch’s informatic assumptions. Lutz Polley (2000) has produced Born rule derivations where the informatic assumptions are replaced by symmetry arguments.

The Born rule and the collapse of the wave function have been obtained in the framework of the relative-state formulation of quantum mechanics by Armando V.D.B. Assis. He has proved that the Born rule and the collapse of the wave function follow from a game-theoretical strategy, namely the Nash equilibrium within a von Neumann zero-sum game between nature and observer.

is there enough room inside this box to swing this cat?

is there enough room inside this box to swing this cat?

I see the Copenhagen interpretation as a mere description of quantum mechanical behaviour as seen from the experimenter’s point of view. Thus, it is correct (presumably), but not an explanation.

KJW said:

It is my view that quantum decoherence within the correct version of the many-worlds interpretation does resolve the measurement problem. The key point is to understand that the different classical states within the multiverse are orthogonal components of the universal quantum state. Orthogonal components do not interfere with each other, which is why the different classical states cannot observe each other. Interference occurs when two non-orthogonal components are combined, and it is within the microscopic realm that one has significantly non-orthogonal components. In the classical realm, the dimension of the multi-particle quantum state is so large that the probability of two randomly chosen quantum states differing significantly from orthogonality becomes negligible. This is why classical states are orthogonal.

If one views the Born rule as a mathematical abstraction of the description what a measurement ultimately does (disregarding the particular details of the measurement process), i.e. the decomposition of a quantum state into its orthogonal components in the observable-dependent basis, then the above is in a way an explanation of the Born rule.

KJW said:

KJW said:

It is my view that quantum decoherence within the correct version of the many-worlds interpretation does resolve the measurement problem. The key point is to understand that the different classical states within the multiverse are orthogonal components of the universal quantum state. Orthogonal components do not interfere with each other, which is why the different classical states cannot observe each other. Interference occurs when two non-orthogonal components are combined, and it is within the microscopic realm that one has significantly non-orthogonal components. In the classical realm, the dimension of the multi-particle quantum state is so large that the probability of two randomly chosen quantum states differing significantly from orthogonality becomes negligible. This is why classical states are orthogonal.

If one views the Born rule as a mathematical abstraction of the description what a measurement ultimately does (disregarding the particular details of the measurement process), i.e. the decomposition of a quantum state into its orthogonal components in the observable-dependent basis, then the above is in a way an explanation of the Born rule.

That sounds reasonable.

OTOH, “the probability of two randomly chosen quantum states differing significantly from orthogonality becomes negligible” but not zero. So there are still a non-zero number of worlds where the probabilities don’t satisfy the Born rule. And I can’t see a way to rule out such worlds, apart from invoking new physics that somehow inhibits such branches.

PM 2Ring said:

OTOH, “the probability of two randomly chosen quantum states differing significantly from orthogonality becomes negligible” but not zero. So there are still a non-zero number of worlds where the probabilities don’t satisfy the Born rule. And I can’t see a way to rule out such worlds, apart from invoking new physics that somehow inhibits such branches.

A classical state is an idealisation anyway, just as Newton’s gravitation is an idealisation of GR or the ideal gas law is an idealisation of real gas behaviour. A real macroscopic state will exhibit interference but the effect is at the same order of magnitude as the interference of microscopic states which is negligible relative to the macroscopic scale. There is no sharp boundary between the quantum and the classical, just that the quantum becomes relatively smaller as the scale is increased.

The thing to note is that a measuring device that measures position (for example) is specifically designed to interact with the position eigenstates of a particle in such a way that each position eigenstate leads to a distinct macroscopic configuration of the measuring device (if it didn’t do this, it wouldn’t be a position measuring device). This means that the microscopic components of the measuring device need to be strongly correlated into a state that resembles the measured position result. But there will still be quantum superpositions within the microscopic components so that the one classical state cannot really be regarded as a single state, but as a quantum superposition of the microscopic variations within the measuring device.

KJW said:

A classical state is an idealisation anyway, just as Newton’s gravitation is an idealisation of GR or the ideal gas law is an idealisation of real gas behaviour.

… or the second law of thermodynamics is an idealisation. (A much closer comparison)

KJW said:

There is no sharp boundary between the quantum and the classical, just that the quantum becomes relatively smaller as the scale is increased.

This is a strength of the many-worlds interpretation – it makes no qualitative distinction between the classical realm and the quantum realm. The action of any system is scaled in terms of the Planck constant, giving a dimensionless value that determines the degree of classicality of the system, with the system being truly classical only in the limit of infinite action. Interpretations that involve wavefunction collapse imply a qualitative distinction between the quantum realm and the classical realm by assuming that a measurement causes a conversion from the quantum realm to the classical realm. By contrast, in the many-worlds interpretation, a measurement merely entangles the superposition components of a microscopic state to the corresponding superposition components of a macroscopic state, with each component of the observer state observing only one component of the microscopic state because that is the component they are entangled with.

Note that the peculiarities of quantum entanglement are best explained by the many-worlds interpretation because quantum entanglement is itself a natural part of the many-worlds interpretation. It is also worth noting that the multi-particle quantum state is better understood in the context of the many-worlds interpretation than in any interpretation that tries to enforce a single reality.

The Rev Dodgson said:

I also thought that illustrating the absurdity of giving special status to human observations was the point that Schrodinger wanted to make

From an objective perspective, there is nothing special about the human observer. But the human observer does provide the first-person perspective that should not be overlooked. Thus, interpretations such as the many-minds interpretation are worthy of consideration, and even in the many-worlds interpretation, the first-person perspective seems crucial to its full understanding. However, because it is the first-person nature of the observer rather than consciousness that is important, the role of the cat as the observer is irrelevant.

The cat either knows it’s alive (if cats actually know such things) or is not in a position to care.

Although I suppose a “many-minds” cat would still be alive, come what may. If we identify the many-minds critters as individuals, which seems highly debatable.

Bubblecar said:

The cat either knows it’s alive (if cats actually know such things) or is not in a position to care.

Well the cat can hardly know that it’s dead. But the point is that what the cat knows is irrelevant to the human observer or the outcome of the experiment.

Bubblecar said:

Although I suppose a “many-minds” cat would still be alive, come what may. If we identify the many-minds critters as individuals, which seems highly debatable.

In the quantum suicide thought experiment, one considers the cat’s point of view.

KJW said:

Bubblecar said:

Although I suppose a “many-minds” cat would still be alive, come what may. If we identify the many-minds critters as individuals, which seems highly debatable.

In the quantum suicide thought experiment, one considers the cat’s point of view.

But is it really the same cat?

Bubblecar said:

KJW said:

Bubblecar said:

Although I suppose a “many-minds” cat would still be alive, come what may. If we identify the many-minds critters as individuals, which seems highly debatable.

In the quantum suicide thought experiment, one considers the cat’s point of view.

But is it really the same cat?

there is only one (borg)cat

Bubblecar said:

But is it really the same cat?

It’s actually a modified experiment whereby the life-terminating decision occurs every 10 seconds.

>In response to questions about “subjective immortality”, Max Tegmark made some brief comments: He acknowledged the argument that “everyone will be immortal” should follow if a survivor outcome is possible for all life-threatening events. The flaw in that argument, he suggests, is that dying is rarely a binary event; it is a progressive process. The quantum suicide thought experiment attempts to isolate all possible outcomes for the duration of the thought experiment. That isolation delays decoherence in such a way that the subjective experience of the superposition is illustrated. It is only within the confines of such an abstract quantum scenario that an observer finds they defy all odds.<

Makes sense. If you’re dying of old age, you can’t keep carving time up tinier and tinier to never die of old age.

KJW said:

Bubblecar said:

The cat either knows it’s alive (if cats actually know such things) or is not in a position to care.

Well the cat can hardly know that it’s dead. But the point is that what the cat knows is irrelevant to the human observer or the outcome of the experiment.

That depends on what you consider to be the outcome of the experiment.

What do you consider to be the outcome of the experiment?

The Rev Dodgson said:

KJW said:

Bubblecar said:

The cat either knows it’s alive (if cats actually know such things) or is not in a position to care.

Well the cat can hardly know that it’s dead. But the point is that what the cat knows is irrelevant to the human observer or the outcome of the experiment.

That depends on what you consider to be the outcome of the experiment.

What do you consider to be the outcome of the experiment?

Ongoing speculation?

Riff-in-Thyme said:

The Rev Dodgson said:

KJW said:

Well the cat can hardly know that it’s dead. But the point is that what the cat knows is irrelevant to the human observer or the outcome of the experiment.

That depends on what you consider to be the outcome of the experiment.

What do you consider to be the outcome of the experiment?

Ongoing speculation?

To demonstrate uncertainty, ie quantum effects?

The Rev Dodgson said:

KJW said:

Bubblecar said:

The cat either knows it’s alive (if cats actually know such things) or is not in a position to care.

Well the cat can hardly know that it’s dead. But the point is that what the cat knows is irrelevant to the human observer or the outcome of the experiment.

That depends on what you consider to be the outcome of the experiment.

What do you consider to be the outcome of the experiment?

Objectively, half the universes in the multiverse where the experiment occurs will have a live cat and the other half a dead cat. But from the perspective of the human experimenter, the cat will either be alive or dead with a 50% probability either way. The point is that there is one special observer who has the first-person perspective.

KJW said:

The Rev Dodgson said:

KJW said:

Well the cat can hardly know that it’s dead. But the point is that what the cat knows is irrelevant to the human observer or the outcome of the experiment.

That depends on what you consider to be the outcome of the experiment.

What do you consider to be the outcome of the experiment?

Objectively, half the universes in the multiverse where the experiment occurs will have a live cat and the other half a dead cat. But from the perspective of the human experimenter, the cat will either be alive or dead with a 50% probability either way. The point is that there is one special observer who has the first-person perspective.

There seem to be some large assumptions in that conclusion.

The Rev Dodgson said:

KJW said:

Objectively, half the universes in the multiverse where the experiment occurs will have a live cat and the other half a dead cat. But from the perspective of the human experimenter, the cat will either be alive or dead with a 50% probability either way. The point is that there is one special observer who has the first-person perspective.

There seem to be some large assumptions in that conclusion.

The second and third sentences seem uncontroversial to me, so I guess you’re referring to the first. The fact of the matter is that quantum mechanics has produced experimental results that fly in the face of common sense and intuition. Reality is quite simply not what it seems to be. Furthermore, a mathematical formalism has been developed to describe the results of quantum mechanics and this formalism has passed a wide variety of experimental testing. Considering these two together, the many-worlds interpretation is the simplest explanation that naturally follows from the formalism. It is even simpler than the Copenhagen interpretation because it doesn’t have the collapse of the wavefunction and treats the process of measurement in a natural way (ok, the nature of multi-particle quantum states is mathematically abstract, but this is part of the mathematical formalism of quantum mechanics rather than its interpretation). So the “large assumptions” you mention are really based on the results of experiments that investigate the nature of quantum mechanics, and are not merely “invisible pink unicorns”.

KJW said:

The Rev Dodgson said:

KJW said:

Objectively, half the universes in the multiverse where the experiment occurs will have a live cat and the other half a dead cat. But from the perspective of the human experimenter, the cat will either be alive or dead with a 50% probability either way. The point is that there is one special observer who has the first-person perspective.

There seem to be some large assumptions in that conclusion.

The second and third sentences seem uncontroversial to me, so I guess you’re referring to the first. The fact of the matter is that quantum mechanics has produced experimental results that fly in the face of common sense and intuition. Reality is quite simply not what it seems to be. Furthermore, a mathematical formalism has been developed to describe the results of quantum mechanics and this formalism has passed a wide variety of experimental testing. Considering these two together, the many-worlds interpretation is the simplest explanation that naturally follows from the formalism. It is even simpler than the Copenhagen interpretation because it doesn’t have the collapse of the wavefunction and treats the process of measurement in a natural way (ok, the nature of multi-particle quantum states is mathematically abstract, but this is part of the mathematical formalism of quantum mechanics rather than its interpretation). So the “large assumptions” you mention are really based on the results of experiments that investigate the nature of quantum mechanics, and are not merely “invisible pink unicorns”.

Through comprehending your take on multiverse I think there are definitely points that can be argued regarding things like “the eternal soul”, if one regards “eternal” as the sum of all possible outcomes.

A problem people seem to have with the many-worlds interpretation is the notion of splitting of universes at each decision point. I think this is the wrong way to view it, and it’s not clear to me that this is really part of the standard many-worlds interpretation or a misrepresentation of it. The true reality in which we exist isn’t spacetime at all, but the entire multiverse. However, as we progressively become entangled to particular past eigenstates, the reality we experience becomes smaller and more like spacetime, and the quantum states become the quantum analogue of conditional probabilities relative to those past eigenstates.

>The true reality in which we exist isn’t spacetime at all, but the entire multiverse.

Do you think you could demonstrate that to Einstein’s satisfaction?

KJW said:

A problem people seem to have with the many-worlds interpretation is the notion of splitting of universes at each decision point. I think this is the wrong way to view it, and it’s not clear to me that this is really part of the standard many-worlds interpretation or a misrepresentation of it. The true reality in which we exist isn’t spacetime at all, but the entire multiverse. However, as we progressively become entangled to particular past eigenstates, the reality we experience becomes smaller and more like spacetime, and the quantum states become the quantum analogue of conditional probabilities relative to those past eigenstates.

The interpretation I last referred to would not include the splitting of universes at decision points. The practical intention of “making a choice” is to narrow the possibilities of the result and so relies on the mechanism you describe here. Without a divergence of superposition, might it not be possible to start with a result and experience all possible choices?

Bubblecar said:

>The true reality in which we exist isn’t spacetime at all, but the entire multiverse.

Do you think you could demonstrate that to Einstein’s satisfaction?

I think it is quite possible

Riff-in-Thyme said:

Bubblecar said:

>The true reality in which we exist isn’t spacetime at all, but the entire multiverse.

Do you think you could demonstrate that to Einstein’s satisfaction?

I think it is quite possible

Short of the fact that there would be little way to actually check on Einsteins level of satisfaction.

Riff-in-Thyme said:

KJW said:

A problem people seem to have with the many-worlds interpretation is the notion of splitting of universes at each decision point. I think this is the wrong way to view it, and it’s not clear to me that this is really part of the standard many-worlds interpretation or a misrepresentation of it. The true reality in which we exist isn’t spacetime at all, but the entire multiverse. However, as we progressively become entangled to particular past eigenstates, the reality we experience becomes smaller and more like spacetime, and the quantum states become the quantum analogue of conditional probabilities relative to those past eigenstates.

The interpretation I last referred to would not include the splitting of universes at decision points. The practical intention of “making a choice” is to narrow the possibilities of the result and so relies on the mechanism you describe here. Without a divergence of superposition, might it not be possible to start with a result and experience all possible choices?

The last question is one example of a way to explore the multiverse question. I might need a little more time to illustrate the various scenarios that have begun to occur to me through examining your explanations KJW.

Bubblecar said:

Do you think you could demonstrate that to Einstein’s satisfaction?

I see the multiverse as a configuration space of every possible spacetime (or similar notion), a space in which entire spacetimes are points. But instead of considering reality as a single point in this space, I consider it as a distribution over this space. So for example, a photon passes through both slits in the double-slit experiment. But it can’t do that in a single spacetime. It requires two distinct spacetimes. However, it is occurring in a single reality, and therefore reality must include at least those two distinct spacetimes. A key aspect is that an observer can both be a single component of a superposition as well as observe a superposition.

Riff-in-Thyme said:

The interpretation I last referred to would not include the splitting of universes at decision points. The practical intention of “making a choice” is to narrow the possibilities of the result and so relies on the mechanism you describe here. Without a divergence of superposition, might it not be possible to start with a result and experience all possible choices?

I should point out that the randomness of quantum mechanics occurs because the superposition component that I identify as “me” can become entangled with any of the eigenstates of a given measurement, but there is a one-to-one deterministic correspondence between the eigenstates of a measurement and the components of the superposition of observers who identify as “me”. In technical language, quantum states evolve unitarily.

Riff-in-Thyme said:

The last question is one example of a way to explore the multiverse question.

The entire multiverse cannot be explored because we cannot observe the parts of the multiverse that we are not entangled with. Instead we consider quantum states that we can observe, for example, in the double-slit experiment. It has been said that the double-slit experiment contains essentially all the strangeness of quantum mechanics.

KJW said:

Riff-in-Thyme said:

The last question is one example of a way to explore the multiverse question.

The entire multiverse cannot be explored because we cannot observe the parts of the multiverse that we are not entangled with. Instead we consider quantum states that we can observe, for example, in the double-slit experiment. It has been said that the double-slit experiment contains essentially all the strangeness of quantum mechanics.

But isn’t this only a particular condition of the observer we must accept while we are attached to reality? The observer we identify may not be the only possible variation of the observer quantity?

Riff-in-Thyme said:

Riff-in-Thyme said:

KJW said:

A problem people seem to have with the many-worlds interpretation is the notion of splitting of universes at each decision point. I think this is the wrong way to view it, and it’s not clear to me that this is really part of the standard many-worlds interpretation or a misrepresentation of it. The true reality in which we exist isn’t spacetime at all, but the entire multiverse. However, as we progressively become entangled to particular past eigenstates, the reality we experience becomes smaller and more like spacetime, and the quantum states become the quantum analogue of conditional probabilities relative to those past eigenstates.

When the eigenstate taken is chosen through critical selection, the result can be considered a refining of the reality of the observer. You state that the reality subsequently becomes “smaller and more like spacetime” but this seems to be open to interpretation, as the nature of such a refined reality may provide that the observer has greater access to the overall system.

Riff-in-Thyme said:

KJW said:

A problem people seem to have with the many-worlds interpretation is the notion of splitting of universes at each decision point. I think this is the wrong way to view it, and it’s not clear to me that this is really part of the standard many-worlds interpretation or a misrepresentation of it. The true reality in which we exist isn’t spacetime at all, but the entire multiverse. However, as we progressively become entangled to particular past eigenstates, the reality we experience becomes smaller and more like spacetime, and the quantum states become the quantum analogue of conditional probabilities relative to those past eigenstates.

When the eigenstate taken is chosen through critical selection, the result can be considered a refining of the reality of the observer. You state that the reality subsequently becomes “smaller and more like spacetime” but this seems to be open to interpretation, as the nature of such a refined reality may provide that the observer has greater access to the overall system.

A Dr Who type character might provide a fair analogy. Putting aside the shows requirement for relevant drama, a genuine timelord would speak or act when it produced the most complete result. A complete result in this sense might be interpreted as one that retains the potentials of all its eigenstates. To clothe this concept in the guise of a timelord might create an individual who’s observable physical timeline appears essentially little different to any other, but who’s immersion within and effect upon the universal reality is far more extensive than is usual.

Riff-in-Thyme said:

When the eigenstate taken is chosen through critical selection, the result can be considered a refining of the reality of the observer.

The eigenstate isn’t “chosen”. That’s the essential part of the many-worlds interpretation. All eigenstates actually exist and have their respective effects on the corresponding realities. It is quantum entanglement between the observer and the eigenstate that makes the eigenstate appear to be chosen from the point of view of the observer.

Riff-in-Thyme said:

You state that the reality subsequently becomes “smaller and more like spacetime” but this seems to be open to interpretation, as the nature of such a refined reality may provide that the observer has greater access to the overall system.

When two systems interact, the state of one system becomes dependent on the state of the other system. This is what entanglement is about. It is a consistency between the two systems that result from the interaction. But when the two systems are each part of quantum superposition, each component of the superposition is still required to satisfy the consistency of the interaction. Thus for example, the specific nature of the present depends on the past being of a particular form and we are not going to have a past that is inconsistent with the present. But the multiverse will contain pasts that are quite different to the past we have. However, those pasts did not lead to our present and therefore do not exist as far as we are concerned. When I said that reality becomes “smaller and more like spacetime”, this was another way of saying that we have more information about our reality, and this information excludes realities where the information is different. It is more like spacetime because there is less superposition of possibilities (spacetime is an exact notion, which is why general relativity is a purely classical theory).

KJW said:

Riff-in-Thyme said:

When the eigenstate taken is chosen through critical selection, the result can be considered a refining of the reality of the observer.

The eigenstate isn’t “chosen”. That’s the essential part of the many-worlds interpretation. All eigenstates actually exist and have their respective effects on the corresponding realities. It is quantum entanglement between the observer and the eigenstate that makes the eigenstate appear to be chosen from the point of view of the observer.
<<<<<<<<<

That line would have been clearer stated as “when a path is chosen through critical selection”.

Riff-in-Thyme said:

You state that the reality subsequently becomes “smaller and more like spacetime” but this seems to be open to interpretation, as the nature of such a refined reality may provide that the observer has greater access to the overall system.

When two systems interact, the state of one system becomes dependent on the state of the other system. This is what entanglement is about. It is a consistency between the two systems that result from the interaction. But when the two systems are each part of quantum superposition, each component of the superposition is still required to satisfy the consistency of the interaction. Thus for example, the specific nature of the present depends on the past being of a particular form and we are not going to have a past that is inconsistent with the present. But the multiverse will contain pasts that are quite different to the past we have. However, those pasts did not lead to our present and therefore do not exist as far as we are concerned. When I said that reality becomes “smaller and more like spacetime”, this was another way of saying that we have more information about our reality, and this information excludes realities where the information is different. It is more like spacetime because there is less superposition of possibilities (spacetime is an exact notion, which is why general relativity is a purely classical theory).

Does this assert that two results whose observable quantities are indistinguishable from each other are not identical if the “pasts” that produced them are not also identical?

KJW said:

But when the two systems are each part of a quantum superposition, each component of the superposition is still required to satisfy the consistency of the interaction.

This is one place where quantum theory distinguishes itself from classical theory via Bell’s theorem. Consider two particles that are allowed to interact then widely separated. The state of one particle will depend on the state of the other particle. However, even if each of the particles are a superposition of states, the dependency between the two particles is still maintained so that even though the measured value for one of the particles is random, the measured value for the other particle will remain consistent with this value, even to the extent of violating the classical probabilities.

KJW said:

KJW said:

But when the two systems are each part of a quantum superposition, each component of the superposition is still required to satisfy the consistency of the interaction.

This is one place where quantum theory distinguishes itself from classical theory via Bell’s theorem. Consider two particles that are allowed to interact then widely separated. The state of one particle will depend on the state of the other particle. However, even if each of the particles are a superposition of states, the dependency between the two particles is still maintained so that even though the measured value for one of the particles is random, the measured value for the other particle will remain consistent with this value, even to the extent of violating the classical probabilities.

How does this effect the results of one particle being involved in a system that requires conforming to classical probabilities?

Riff-in-Thyme said:

Does this assert that two results whose observable quantities are indistinguishable from each other are not identical if the “pasts” that produced them are not also identical?

If the experimental setup was independent of the particular past, then no.

Riff-in-Thyme said:

How does this effect the results of one particle being involved in a system that requires conforming to classical probabilities?

Why would that be the case?

The point I was making concerned the nature of quantum superposition and entanglement and how it can’t be explained by classical physics.

KJW said:

Riff-in-Thyme said:

How does this effect the results of one particle being involved in a system that requires conforming to classical probabilities?

Why would that be the case?

Not sure any more. I got distracted by soundwaves creating photons in air bubbles they collapse and that level of coherence has dissipated from my thinking for now.

KJW said:

The point I was making concerned the nature of quantum superposition and entanglement and how it can’t be explained by classical physics.

A specific example is a pair of electrons in the singlet state. This consists of one electron with spin-up and the other electron with spin-down. It is a particular superposition of the up-down and down-up two-electron states. This quantum state is spherically symmetric, which is more symmetric than is possible by any classical view of a pair of spin directions.

KJW said:

KJW said:

The point I was making concerned the nature of quantum superposition and entanglement and how it can’t be explained by classical physics.

A specific example is a pair of electrons in the singlet state. This consists of one electron with spin-up and the other electron with spin-down. It is a particular superposition of the up-down and down-up two-electron states. This quantum state is spherically symmetric, which is more symmetric than is possible by any classical view of a pair of spin directions.

It seems easier to illustrate this area on the micro scale than macro, which is part of the direction my questions have taken.

Riff-in-Thyme said:

It seems easier to illustrate this area on the micro scale than macro

Of course. Ultimately, this topic of this thread is about the distinction between the microscopic scale and the macroscopic scale. What happens at the microscopic scale clearly can’t be explained by classical physics and requires a shift in the way we view reality. However, why should the macroscopic scale be any different, qualitatively speaking? The scale of the quantum effects will be relatively smaller, but will still be present.

the arrest only robocop could make

Schrodinger!!! Dead and alive, you’re coming with me.

“What’s the charge?”

“He’s a cat killer!”

As I see it, the many-worlds interpretation is the only interpretation in which the quantum state can be both real and not violate general relativity. Interpretations that involve the collapse of a real wavefunction violate general relativity because general relativity is a local theory and wavefunction collapse is non-local. And interpretations where the wavefunction is not real violate quantum mechanics according to this article. But the quantum state of the many-worlds interpretation is real because the multiverse is regarded as real, and doesn’t violate general relativity because it is outside the domain of general relativity.

KJW said:

KJW said:

The point I was making concerned the nature of quantum superposition and entanglement and how it can’t be explained by classical physics.

A specific example is a pair of electrons in the singlet state. This consists of one electron with spin-up and the other electron with spin-down. It is a particular superposition of the up-down and down-up two-electron states. This quantum state is spherically symmetric, which is more symmetric than is possible by any classical view of a pair of spin directions.

Can you provide more detail on the last line here please?

Riff-in-Thyme said:

KJW said:

A specific example is a pair of electrons in the singlet state. This consists of one electron with spin-up and the other electron with spin-down. It is a particular superposition of the up-down and down-up two-electron states. This quantum state is spherically symmetric, which is more symmetric than is possible by any classical view of a pair of spin directions.

Can you provide more detail on the last line here please?

Consider any pair of arrows (representing directions of the electron spin). No matter how you arrange these in space, that arrangement will not be spherically symmetric, by which is meant that rotating the arrangement will lead to a different arrangement. By contrast, rotating the electron pair singlet quantum state will always produce the same quantum state. Regardless of how this quantum state is rotated, any experiment will produce the same result.

KJW said:

Riff-in-Thyme said:

KJW said:

A specific example is a pair of electrons in the singlet state. This consists of one electron with spin-up and the other electron with spin-down. It is a particular superposition of the up-down and down-up two-electron states. This quantum state is spherically symmetric, which is more symmetric than is possible by any classical view of a pair of spin directions.

Can you provide more detail on the last line here please?

Consider any pair of arrows (representing directions of the electron spin). No matter how you arrange these in space, that arrangement will not be spherically symmetric, by which is meant that rotating the arrangement will lead to a different arrangement. By contrast, rotating the electron pair singlet quantum state will always produce the same quantum state. Regardless of how this quantum state is rotated, any experiment will produce the same result.

but how is that more symmetric than is possible in a classical view?

Riff-in-Thyme said:

but how is that more symmetric than is possible in a classical view?

Because the classical view can’t produce spherical symmetry.

The non-classical consequence of the spherical symmetry is that even though the spins of the two electrons are exactly opposite to each other, one can’t attribute any direction to the spin of either electron.

KJW said:

The non-classical consequence of the spherical symmetry is that even though the spins of the two electrons are exactly opposite to each other, one can’t attribute any direction to the spin of either electron.

gotcha

KJW said:

The non-classical consequence of the spherical symmetry is that even though the spins of the two electrons are exactly opposite to each other, one can’t attribute any direction to the spin of either electron.

That’s one example of the non-classical aspect of quantum entanglement which can occur when one has a quantum superposition of two-particle states: the two particles may have the same (or opposite) values for some quantity, yet not have a definite value for that quantity. The two particles may be very far apart, yet measuring one of the particles measures the other particle. This is what Einstein referred to as “spooky action at a distance”.