Quantum Superposition & Philosophy

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Quantum physics suggests that unobserved particles exist as wave functions with infinite possibilities, collapsing into a definite state only upon observation. This leads to philosophical questions, such as George Berkeley's idea that unperceived objects, like trees, may not exist in a traditional sense. Experiments with larger particles, like bucky-balls, show they can also exhibit interference, challenging the notion of existence without observation. The discussion highlights the complexities of superposition and the impact of environmental interactions on larger objects, suggesting that superposition states are difficult to maintain due to constant information leakage. Ultimately, the conversation navigates the intersection of quantum mechanics and philosophical implications regarding existence and perception.
Elvin12
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According to Quantum Physics (or at least my understanding of it), when a particle is not observed it doesn't exist in the way one imagines is to be. Instead, it is a wave function with infinite possibilities (sum-over histories by Feynman), and only when observed it takes on a definite state. This what I got from books that I've read, but its still quite hard to understand as how a particle interferes with itself while traveling through a double-slit and why exactly is it the observer that chooses the fate of Scholidinger's cat in the box?
One other thing I'm wondering has more to do with philosophy but can be tied in here also. Geroge Berkeley said that if no one looks at a tree, it doesn't exist, in other words "esse est percipi" or "to be is to be perceived". Scientists have found that even particles large enough to be observed by microscopes (bucky-balls) also interfere. So I'm wondering whether George Berkley is right, and a tree doesn't exist if not perceived, but rather a wave function with infinite different possibilities?
If what I said makes no sense, I apologize, but please correct me so I have a better understanding.
 
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Elvin12 said:
According to Quantum Physics (or at least my understanding of it), when a particle is not observed it doesn't exist in the way one imagines is to be. Instead, it is a wave function with infinite possibilities (sum-over histories by Feynman), and only when observed it takes on a definite state. This what I got from books that I've read, but its still quite hard to understand as how a particle interferes with itself while traveling through a double-slit and why exactly is it the observer that chooses the fate of Scholidinger's cat in the box?
One other thing I'm wondering has more to do with philosophy but can be tied in here also. Geroge Berkeley said that if no one looks at a tree, it doesn't exist, in other words "esse est percipi" or "to be is to be perceived". Scientists have found that even particles large enough to be observed by microscopes (bucky-balls) also interfere. So I'm wondering whether George Berkley is right, and a tree doesn't exist if not perceived, but rather a wave function with infinite different possibilities?
If what I said makes no sense, I apologize, but please correct me so I have a better understanding.

not on nonlinear quantum mechanics (unlike standard quantum mechanics).
 
StevieTNZ said:
There was an interesting article published by Nature earlier this year entitled 'No Moon There'. You can read it here: http://www.engr.ucr.edu/~korotkov/news/2010-NatPhys.pdf

i read it time ago.
i waiting the result on more big object like:

http://www.fqxi.org/community/articles/display/103

Tejinder Singh
http://arxiv.org/abs/0711.3773

argues that quantum theory is intrinsically nonlinear, and goes to the standard linear limit for microscopic objects. THe nonlinear theory goes to the classical limit for large objects, but departs from linear quantum mechanics for mesoscopic objects.

Because of the nonlinearity, the lifetime of two superposed states is no longer infinite. It decreases as the number of atoms in the object under study increases, going from an astronomically large value for microsystems, to extremely small values for macrosystems. Thus somewhere in between, the superposition lifetime ought to be measureable in the laboratory.


----------------------
in any case the final theory have to be nonlinear.
read:
https://www.physicsforums.com/showthread.php?t=374854

-----------------
http://arstechnica.com/science/news/2009/10/quantum-gravity-theories-meet-a-gamma-ray-burst.ars

...A value this close to the Planck length means that quantum gravity models in which there's a linear relationship between photon energy and speed are "highly implausible" That leaves other quantum gravity options open, including those in which the the relationship is non-linear. Hopefully, theoreticians will be able to devise real-world tests for some of these...
 
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What is the difference between linear and nonlinear quantum mechanics (perferably without all the mathematics).
 
StevieTNZ said:
What is the difference between linear and nonlinear quantum mechanics (perferably without all the mathematics).

the linearity refers to the fact that there is no change (superposition stay forever, there is no collapse) is "LINEAR" (linear schrodinger equation).
in nonlinear model things change, there is breakdown of superposition, there is a collapse (nonlinear schrodinger equation).


...suppose you make a quantum measurement of an observable of a quantum system which is in a superposition of two states. The way nonlinearity destroys superposition is as follows : when a measurement begins, one of the two states starts to grow exponentially, while the other starts to decay exponentially......
 
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yoda jedi said:
...suppose you make a quantum measurement of an observable of a quantum system which is in a superposition of two states. The way nonlinearity destroys superposition is as follows : when a measurement begins, one of the two states starts to grow exponentially, while the other starts to decay exponentially......
I wouldn't call that "destroying" the superposition. What you're describing is just a superposition that leads to predictions that are practically indistinguishable from the predictions derived from an eigenstate. This wouldn't get rid of the philosophical problems associated with the (IMO misguided) assumption that the wavefunction describes a single reality.
 
Fredrik said:
I wouldn't call that "destroying" the superposition. What you're describing is just a superposition that leads to predictions that are practically indistinguishable from the predictions derived from an eigenstate. This wouldn't get rid of the philosophical problems associated with the (IMO misguided) assumption that the wavefunction describes a single reality.

collapse=no superposition
 
  • #10
yoda jedi said:
collapse=no superposition
Yes, but "exponentially decaying magnitude of the coefficients of all but one term in a superposition" ≠ collapse.
 
  • #11
Fredrik said:
Yes, but "exponentially decaying magnitude of the coefficients of all but one term in a superposition" ≠ collapse.

and

Fredrik said:
to predictions that are practically indistinguishable from the predictions derived

double answer:

...The growth/decay process can be said to be `complete' over some calculable time scale tau. Now suppose we were to suddenly take away the measuring apparatus `during' the measurement, [i.e. after a time less than tau since the start of measurement] the state we will be left with is a certain superposition of the two states of the kind that is not seen in ordinary quantum mechanics. It is a sum of an exponentially grown state and an exponentially decayed state - this prediction is different from quantum mechanics. If we feed such a state into a second measuring apparatus, `quickly' after the first partial measurement, the outcome will be different from that predicted by quantum mechanics......
 
  • #12
In answer to the OP:

There is a large difference between a Tree and the bucky-balls of that experiment, and that is that the tree is interacting with it's environment. It may not have any human observing it, but there are still many other things that "observe" it, in the form of being in contact with it, such as the air, and the ground it stands on etc. The significance of these things is that information about the trees existence constantly leaks into the rest of the world, making it impossible to remain in a superposition state.

You will find that for all the experiments that are being done with large quantum objects, the single most difficult things to accomplish experimentally, is to be able to create enough isolation of the object from the rest of the world, and even "from itself" because even the objects own different internal degrees of freedom can destroy superposition states. The latter usually means that you have to cool the object down to it's motional ground state, which rapidly becomes harder and harder to do with increasing object size.
 
  • #13
So what you're saying, Zargon, is that the object perceives itself or is perceived by its environment, so that there is no real superposition or it's only momentary which would collapse the MWI.
 
  • #14
SprocketPower said:
So what you're saying, Zargon, is that the object perceives itself or is perceived by its environment, so that there is no real superposition or it's only momentary which would collapse the MWI.

there are no collapses on MWI.
the objectification is due to a process called "Environment Induced Superselection"
and the other branches (superpositions) goes according the MWI.
 
  • #15
By "would collapse the MWI" I meant that the theory would not hold. I take it from your answer it still would.
 
  • #16
No, I did not mix MWI or any other interpretation into my statement. What I said is true regardless of beliefs, beucase all interpretations agree (as far as we know today) on measurement outcomes, and in this case the probability amplitude for the tree being there is always 1. I was just saying that the reason that such a large object as a tree won't be in a superposition state is because of all it's near-infinite number of degrees of freedom (for example vibrational and rotational modes between the molecules), and because all of the connections that it has to other objects. The wavefunction will never be isolated enough that you could get to a point where no information leaks out, destroying the superposition.


Also, the tree being there or not suffers from additional problems, such as violating energy conservation. If you look at the quantum experiments that deals with superpositions, you will see that they conserve all properties. An typical example is a single ion being in a superposition of either "being excited" or "being in ground state + there being an extra photon equal to the energy difference between the states". In the tree case you would first have to define a state that has the matching energy/momentum etc. as the tree without there actually being a tree, before one could even begin to talk about superpositions of the states.
 
  • #17
"Any modification of the apparatus that can determine which slit a photon passes through destroys the interference pattern,[5] illustrating the complementarity principle: that light (and electrons, etc.) can behave as either particles or waves, but not both at the same time.[8][9][10] However, an experiment performed in 1987[11] produced results that demonstrated 'which-path' information could be obtained without destroying the possibility of interference. This showed the effect of measurements that disturbed the particles in transit to a lesser degree and thereby influenced the interference pattern only to a comparable extent"
This is from wikipedia page:
http://en.wikipedia.org/wiki/Double-slit_experiment

So what does this mean, that the particle can in fact be observed, but there is a certain limit on how much? wouldn't that prove Objective collapse theory true?
 
  • #18
Elvin12,

Objective collapse is indetermistic, but what about SD? How would that explain superposition?
 
  • #19
an answer to the OP:

I think it depends on the interpretation of quantum physics you prefer. If you would agree with the Copenhagen interpretation you would say it doesn't matter because you could never know anyway. I, with my limited knowledge of the subject, think that the tree is in a constant superposition throughout space, and that we just perceive it to be at a particular place at a certain point in time for whatever reason.

PS. could anyone recommend a book on quantum physics without all the math, something more suitable for someone in high school or pregrad college? i'd appreciate it.
 
  • #20
GodPlaysDice,

I can recommend Quantum World by Ken Ford and Introducing Quantum Theory by McEvoy and Zarate, which I have, but also Understanding Quantum Mechanics by Roland Omnès, Quantum World and Quantum Theory by J.C. Polkinghorne, and Quantum: a Guide for the Perplexed by Jim Al-Khalili, which look to be very good, too, and which I'll probably get also (I have already ordered Quantum Theory by J.C. Polkinghorne).

These are not mathematical and are fairly short but very substantial so are not heavy going. You can get them through Bookfinder.
 
  • #21
SprocketPower,

Thank you, I am looking forward to reading them. I recently read Quantum: A Guide for the Perplexed. I suggest you get it; it explains alternate interpretations of QP well, and also has a great chapter on the history of QP. It is a good book to read if you are a visual learner (it has lots of pictures).
 
  • #22
What you guys fail to include in your theories is the mind and consciousness. You have a broad knowledge of quantum physics yet you don't see the truth held within the facts. You say that the tree isn't in superposition because its information leaks etc. What you fail to recognise is that the tree doesn't even exist. There isn't a single pre-existing feature of reality that is independent of our minds. Our minds are all powerful tools of creation. Therefore instead of discovering the universe we are actually creating the universe around us.
 
  • #23
Another excellent book and movie is 'what the bleep do we know?' . Really life changing. The movie is excellent but the book goes much deeper into QP.
 
  • #24
Silentshado said:
What you guys fail to include in your theories is the mind and consciousness. You have a broad knowledge of quantum physics yet you don't see the truth held within the facts.
And I suppose the fact that you don't understand quantum physics is what helps you see the truth?

Silentshado said:
What you fail to recognise is that the tree doesn't even exist. There isn't a single pre-existing feature of reality that is independent of our minds. Our minds are all powerful tools of creation. Therefore instead of discovering the universe we are actually creating the universe around us.
What predictions does this "theory" make that are different from the predictions made by other theories? What experiments have confirmed that your "theory" makes better predictions than other theories?

The fact that a brain is creating a model of (some aspects of) the world around it, using information about the actual world obtained through the sensory organs, doesn't mean that there isn't an actual world out there.

Silentshado said:
Another excellent book and movie is 'what the bleep do we know?' . Really life changing. The movie is excellent but the book goes much deeper into QP.
I'm sorry, but that movie is complete crackpot nonsense. The people who made it know almost nothing about physics, and they don't understand what science is.
 
  • #25
GodPlaysDice said:
PS. could anyone recommend a book on quantum physics without all the math, something more suitable for someone in high school or pregrad college? i'd appreciate it.
"QED: The strange theory of light and matter", by Richard Feynman.
 
  • #26
Silentshado said:
Another excellent book and movie is 'what the bleep do we know?' . Really life changing. The movie is excellent but the book goes much deeper into QP.

This is a banned topic, see forum rules.
 
  • #27
Silentshado said:
What you guys fail to include in your theories is the mind and consciousness. You have a broad knowledge of quantum physics yet you don't see the truth held within the facts. You say that the tree isn't in superposition because its information leaks etc. What you fail to recognise is that the tree doesn't even exist. There isn't a single pre-existing feature of reality that is independent of our minds. Our minds are all powerful tools of creation. Therefore instead of discovering the universe we are actually creating the universe around us.

If everything in the universe is created by our minds, where did our minds come from? How could something that is (supposedly) not real (our minds) create something else, may it be real or not?
 
  • #28
GodPlaysDice,

Great, I'll certainly buy the Al-Khalili book.
 
  • #29
GodPlaysDice said:
If everything in the universe is created by our minds, where did our minds come from?


Does the opposite approach answer in any way the deep questions? If everything in the universe is not created by our minds, where did the universe come from?


How could something that is (supposedly) not real (our minds) create something else, may it be real or not?

I wonder that too. But how can something supposedly non-existent(universe) create itself, may it be real or not?

How far can we really go by staying totally rational and reasonable, i.e. dismissing anything that doesn't fit our worldview? I am willing to argue that the biggest hinderance towards future progress in science is its past success in building models based on classical-like approximations.
 
  • #30
Maui said:
How far can we really go by staying totally rational and reasonable, i.e. dismissing anything that doesn't fit our worldview? I am willing to argue that the biggest hinderance towards future progress in science is its past success in building models based on classical-like approximations.

I'd go a bit further than merely the success of past approximations in physics and say the problem is as much cultural and innate:

P Merel said:
Ritual
Well established hierarchies are not easily uprooted;
Closely held beliefs are not easily released;
So ritual enthralls generation after generation.
Harmony does not care for harmony, and so is naturally attained;
But ritual is intent upon harmony, and so can not attain it.
Harmony neither acts nor reasons;
Love acts, but without reason;
Justice acts to serve reason;
But ritual acts to enforce reason.
When the Way is lost, there remains harmony;
When harmony is lost, there remains love;
When love is lost, there remains justice;
But when justice is lost, there remains ritual.
Ritual is the end of compassion and honesty,
The beginning of confusion;
Belief is a colourful hope or fear,
The beginning of folly.
The sage goes by harmony, not by hope;
He dwells in the fruit, not the flower;
He accepts substance, and ignores abstraction.
 

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