"You have no responsibility to live up to what other people think you ought to accomplish. I have no responsibility to be like they expect me to be: it's their mistake, not my failing."
I have no illusions about the state of my knowledge of physics. Unfortunately, the same cannot be said of others. Like my friend, who emailed me today with the following question - "Can you explain this to me?"
Umm...
My fault to be sure, for having mentioned quantum physics in conjunction with what I was working on, to the chagrin of actual physicists everywhere. But I love a challenge, and I'm feeling feisty. (Just yesterday I learned how to read a basic space-time diagram of particle interactions. Not to be confused with a Feynman diagram, apparently, though I'm not entirely sure why.) Relatively speaking, I've got a better chance of being able to explain this article than most people, so why not...
Naturally, the preferred method for explaining such things is to refer the questioner to someone who has already explained it better than you could. (Preferably with pictures.) But where's the fun in that?
The first thing to do is to understand Hardy's paradox. In the absence of an article from our usual source - the almighty Wikipedia - we are forced to stray into press releases and blog postings to get our bearings. Hardy's paradox comes from a thought experiment that applies the fundamental tenet of quantum theory - an unobserved particle existing in a superposition of all possible positions - to a particle-antiparticle collision. Hardy reasoned that the attempts to create such a collision (see picture) might result in the particle and antiparticle disturbing each other without actually annihilating each other (as they are required to do by definition) due to their respective half-in half-out quantum states of being. (Curious minds stop to ponder what 'disturb but not annihilate' looks like...)
Hardy's design was previously thought to be untestable, as attempting to measure this 'disturbance' was itself a disturbance. That is, until the advent of interaction-free measurement or weak measurement, which itself violates a basic tenet of quantum physics - that the measurement of quantum systems (systems in a superposition of possible states) fundamentally alters those systems causing them to collapse "back to some kind of normality" (a single state). This kind of 'weak' measurement utilizes a measurement interval which is smaller than the inherent level of uncertainty about the properties of the particle. This means that you don't really know what you've got for any single measurement, but in theory you are able to deduce things from the average of such measurements repeated many times.
Your article reports on a modified test of Hardy's paradox, which used photons instead of particles and antiparticles. (Photons are their own antiparticles.) The claim is that physicists were able measure the system without really measuring it, and can therefore draw conclusions about the real (quantum) state of reality. Actually, this same experiment has been done twice by different groups/labs using the same techniques. And the weirdness is that they found regions which had fewer than zero particles in them. "Fewer than zero particles being present usually means that you have antiparticles instead." But photons are their own antiparticle, so what's going on? The analogy is made to Hardy's improbable hypothetical outcome of particle and antiparticles which disturb but fail to annihilate one another. But other than a shared sense of weirdness - "It looks impossible. But then I realised it was the only way to see it. It's beautiful." (here) - I'm not sure how the analogy applies.
Mind you, I don't have the source articles, so there's a good chance I'm missing something. But as far as I can tell, the point is basically that "there is a way to carry out experiments on the counter-intuitive predictions of quantum theory without destroying all the interesting results" and that "there are extraordinary things within ordinary quantum mechanics."
(That was actually fun! Bring it on!)
Now if you were asking if I can explain what it means, or how it fits with my idea... (sigh)
Tuesday, March 10, 2009
Friday, March 6, 2009
The Age of Entanglement
I am but a tool of the Wikiether. (That will be in a science fiction book one day. Watch for it. ;)
It takes a lot for me to fire up the computer on a Friday night, especially when I had other plans.
Don't get excited. This is probably complete and utter crap. But when something clicks (or appears to click), you listen. And then you write it down.
It has occurred to me that eventually observations of entangled behavior would have to be accounted for by the 5-dimensional model. (I'm skipping words as I type. This is not a good sign.) Tonight it occurred to me that the answer might really be simple after all.
What if observed entanglement behavior is nothing more than a reflection of the transfer or replication of the bias for state selection from the representation of one object to the representation of another?
This idea would have to be supported by massive parallels between the neurophysics of knowledge representation and the known observations of entanglement creation and destruction. We established in our last post that the creation of entanglement is a bizarre process, one which is apparently not as cut-and-dry as I previously believed it to be. When I search for information on the destruction of entanglement, I am delighted to find that there is data on this phenomenon. 'Entanglement Sudden Death' or ESD "can arise when two sources of environmental 'noise' act to disrupt an entangled state. Each source would individually induce a more gradual asymptotic decay, but in tandem they can trigger ESD." (here)
Several minutes elapse while I pursue the 2007 Almeida et al source article. (Via.) And therein I meet the concept of decoherence (again). "[Q]uantum decoherence is the mechanism by which quantum systems interact with their environments to exhibit probabilistically additive behavior... [and] gives the appearance of wave function collapse." (W) (Things click. I feel slightly wiser.) So decoherence is how we avoid the need for an actual wave function collapse, yes? More study is required on my part, I know, but for now it is enough to know that decoherence is a 'theoretical concept' and Almeida's attributed explanation for ESD - "The presence of decoherence in communication channels and computing devices, which stems from the unavoidable interaction between these systems and the environment, degrades the entanglement when the particles propagate or the computation evolves. Decoherence leads to local dynamics, associated with single-particle dissipation, diffusion, and decay, as well as to global dynamics, which may provoke the disappearance of entanglement at a finite time."
The question remains - Can the observed dynamics of entanglement and decoherence be mapped on to the dynamics of knowledge representation? Especially those dynamics which deal with the creation of associations and overlapping representations? This would require a detailed examination of the neural substrates of associative memory, though perhaps on a level that is not currently possible.
Now that I'm rolling on this line of thought... The stability of entanglement (or not) would be a reflection of the stability of the expectation/bias that the two entangled particles would behave as such. The cumulative state of the information about such an entanglement would be spread across multiple observers, and the displayed behavior between the particles would change in response to the shifting bias for state selection (of a particular observation) as anchored by the relevant set of observers.
What would falsify this idea? (The question you should always ask, even if you don't have a ready answer...) Hell if I know, as I barely have even the framework of this idea, let alone the data to support it. But I bet I'm going to lose sleep thinking about it... Damn.
(I warned you that this wasn't going to be pretty. ;)
It takes a lot for me to fire up the computer on a Friday night, especially when I had other plans.
Don't get excited. This is probably complete and utter crap. But when something clicks (or appears to click), you listen. And then you write it down.
It has occurred to me that eventually observations of entangled behavior would have to be accounted for by the 5-dimensional model. (I'm skipping words as I type. This is not a good sign.) Tonight it occurred to me that the answer might really be simple after all.
What if observed entanglement behavior is nothing more than a reflection of the transfer or replication of the bias for state selection from the representation of one object to the representation of another?
This idea would have to be supported by massive parallels between the neurophysics of knowledge representation and the known observations of entanglement creation and destruction. We established in our last post that the creation of entanglement is a bizarre process, one which is apparently not as cut-and-dry as I previously believed it to be. When I search for information on the destruction of entanglement, I am delighted to find that there is data on this phenomenon. 'Entanglement Sudden Death' or ESD "can arise when two sources of environmental 'noise' act to disrupt an entangled state. Each source would individually induce a more gradual asymptotic decay, but in tandem they can trigger ESD." (here)
Several minutes elapse while I pursue the 2007 Almeida et al source article. (Via.) And therein I meet the concept of decoherence (again). "[Q]uantum decoherence is the mechanism by which quantum systems interact with their environments to exhibit probabilistically additive behavior... [and] gives the appearance of wave function collapse." (W) (Things click. I feel slightly wiser.) So decoherence is how we avoid the need for an actual wave function collapse, yes? More study is required on my part, I know, but for now it is enough to know that decoherence is a 'theoretical concept' and Almeida's attributed explanation for ESD - "The presence of decoherence in communication channels and computing devices, which stems from the unavoidable interaction between these systems and the environment, degrades the entanglement when the particles propagate or the computation evolves. Decoherence leads to local dynamics, associated with single-particle dissipation, diffusion, and decay, as well as to global dynamics, which may provoke the disappearance of entanglement at a finite time."
The question remains - Can the observed dynamics of entanglement and decoherence be mapped on to the dynamics of knowledge representation? Especially those dynamics which deal with the creation of associations and overlapping representations? This would require a detailed examination of the neural substrates of associative memory, though perhaps on a level that is not currently possible.
Now that I'm rolling on this line of thought... The stability of entanglement (or not) would be a reflection of the stability of the expectation/bias that the two entangled particles would behave as such. The cumulative state of the information about such an entanglement would be spread across multiple observers, and the displayed behavior between the particles would change in response to the shifting bias for state selection (of a particular observation) as anchored by the relevant set of observers.
What would falsify this idea? (The question you should always ask, even if you don't have a ready answer...) Hell if I know, as I barely have even the framework of this idea, let alone the data to support it. But I bet I'm going to lose sleep thinking about it... Damn.
(I warned you that this wasn't going to be pretty. ;)
Thursday, March 5, 2009
Like A Circus
"I write as a mathematician uses a sheet of paper for doing calculations: because I think better that way."
(Alright, the feedback on this is killing me. Relax.)
The habits of 16 years die hard. The mind asks a question. The question does not go away. If the question does go away, another takes its place. (sigh)
Not too long after the Really Big Idea decided that NOW - right as I was about to become Dr. N, with a career trajectory that went nowhere near physics - was a good time to emerge, I read a book on entanglement. (At this point I was still optimistic that the answer to creating a 5-dimensional model was simple, and that all I had to do was find it.) I won't mention which book, because after finishing it I still didn't understand what entanglement was. I was mildly aggravated that someone could write an entire book on entanglement and still not give a satisfactory explanation of what it was.
'Satisfactory' meaning that I now knew what creates entanglement, as well as how entanglement is destroyed, if/how multiple entanglements are sustained, etc. etc. Since reading that book, it seems to me as though the 'E' word is increasing in popularity, and has become a default explanation for many things. I might go so far as to say that 'entanglement' seems to be the new 'quantum'...
I didn't pay much attention to entanglement while I was developing ideas about the nature of a conscious interface with the 'smear', because I couldn't see a direct link between it and the dynamics of 5-dimensional navigation. (State exclusion seemed to be a more relevant principle.) Which is not to say that there isn't one, simply that I haven't seen one yet and have therefore simply added entanglement to the long list of things that will eventually require explanation. Even certain scientists, whose books we will not name, have said "Particles that are quantum entangled do not imply that signals pass between them. Entanglement means that separated systems are correlated. Psi, on the other hand, seems to involve information transfer, like signal passing." So what does entanglement mean for a 5-dimensional model?
Let's not start with something like this - "let's assume that our bodies, minds, and brains are entangled in a holistic universe." Let's not start with this because there is a process by which particles become entangled. Or at least there was the last time I checked... "When pairs of particles are generated by the decay of other particles, naturally or through induced collision, these pairs may be termed 'entangled', in that such pairs often necessarily have linked and opposite qualities, i.e. of spin or charge." (W)
Which begs the following questions... 1) Do these particles remain entangled forever? 2) What would destroy the entanglement between these two particles? 3) Can a single particle sustain multiple entanglements created at different times with several other particles? (Are particles polygamous or monogamous?) and 4) What about particle threesomes, where a third particle joins a pre-existing entanglement? How has this new addition changed the entanglement relationship between the original two particles? (Why do all these questions bring to mind sexual relationships?) And what's up with this - "The doubly mysterious part of entanglement swapping is that the entangling photons never interact; in normal entanglement, particles must interact and then separate before demonstrating correlative behavior."? I'm getting confused. Are we expanding the ways in which particles can become entangled?
And if one particle is continuously becoming newly-entangled, while retaining all of its previous entanglements unaltered, then is a particle simply the sum total of all of its previous partners? (This opens a new set of questions about the qualitative differences between a particle with few versus many entanglements...) If one particle is continuously becoming newly-entangled, and this causes its previous entanglement obligations to be destroyed or modified in some way, then attempting to use entanglement as an explanation for anything becomes exceedingly difficult, as there is no telling when that entanglement might be/has been destroyed. (Someone out there probably knows which option is correct, and it would be ever so helpful if you would just drop a comment with your explanation. I have the feeling that I'm spinning wheels that don't need to be spun...)
My interest in entanglement is renewed when I read papers like this, which uses entanglement to explain memory (for reasons I'm missing), or articles like this, which talks about the history of the idea of entanglement more so than the properties and limits of entanglement. My interest is further stoked by the notion that entropy provides a measure of entanglement, and a 'connection between quantum information theory and thermodynamics' - a concept which I don't completely understand, but which I nevertheless now fantasize might be the missing link in this 5-dimensional model.
My questions are like a program that is always running in the background, consuming whatever spare resources can be found. They're not going away anytime soon. I know, I know - I should go study physics.
Until that happens though, you'll have the pleasure of listening to a cognitive psychologist butcher, twist, and mangle all of your cherished physics concepts. And it's not going to be pretty. If you're not tired of it already, you'll get there. I promise. :)
(Alright, the feedback on this is killing me. Relax.)
The habits of 16 years die hard. The mind asks a question. The question does not go away. If the question does go away, another takes its place. (sigh)
Not too long after the Really Big Idea decided that NOW - right as I was about to become Dr. N, with a career trajectory that went nowhere near physics - was a good time to emerge, I read a book on entanglement. (At this point I was still optimistic that the answer to creating a 5-dimensional model was simple, and that all I had to do was find it.) I won't mention which book, because after finishing it I still didn't understand what entanglement was. I was mildly aggravated that someone could write an entire book on entanglement and still not give a satisfactory explanation of what it was.
'Satisfactory' meaning that I now knew what creates entanglement, as well as how entanglement is destroyed, if/how multiple entanglements are sustained, etc. etc. Since reading that book, it seems to me as though the 'E' word is increasing in popularity, and has become a default explanation for many things. I might go so far as to say that 'entanglement' seems to be the new 'quantum'...
I didn't pay much attention to entanglement while I was developing ideas about the nature of a conscious interface with the 'smear', because I couldn't see a direct link between it and the dynamics of 5-dimensional navigation. (State exclusion seemed to be a more relevant principle.) Which is not to say that there isn't one, simply that I haven't seen one yet and have therefore simply added entanglement to the long list of things that will eventually require explanation. Even certain scientists, whose books we will not name, have said "Particles that are quantum entangled do not imply that signals pass between them. Entanglement means that separated systems are correlated. Psi, on the other hand, seems to involve information transfer, like signal passing." So what does entanglement mean for a 5-dimensional model?
Let's not start with something like this - "let's assume that our bodies, minds, and brains are entangled in a holistic universe." Let's not start with this because there is a process by which particles become entangled. Or at least there was the last time I checked... "When pairs of particles are generated by the decay of other particles, naturally or through induced collision, these pairs may be termed 'entangled', in that such pairs often necessarily have linked and opposite qualities, i.e. of spin or charge." (W)
Which begs the following questions... 1) Do these particles remain entangled forever? 2) What would destroy the entanglement between these two particles? 3) Can a single particle sustain multiple entanglements created at different times with several other particles? (Are particles polygamous or monogamous?) and 4) What about particle threesomes, where a third particle joins a pre-existing entanglement? How has this new addition changed the entanglement relationship between the original two particles? (Why do all these questions bring to mind sexual relationships?) And what's up with this - "The doubly mysterious part of entanglement swapping is that the entangling photons never interact; in normal entanglement, particles must interact and then separate before demonstrating correlative behavior."? I'm getting confused. Are we expanding the ways in which particles can become entangled?
And if one particle is continuously becoming newly-entangled, while retaining all of its previous entanglements unaltered, then is a particle simply the sum total of all of its previous partners? (This opens a new set of questions about the qualitative differences between a particle with few versus many entanglements...) If one particle is continuously becoming newly-entangled, and this causes its previous entanglement obligations to be destroyed or modified in some way, then attempting to use entanglement as an explanation for anything becomes exceedingly difficult, as there is no telling when that entanglement might be/has been destroyed. (Someone out there probably knows which option is correct, and it would be ever so helpful if you would just drop a comment with your explanation. I have the feeling that I'm spinning wheels that don't need to be spun...)
My interest in entanglement is renewed when I read papers like this, which uses entanglement to explain memory (for reasons I'm missing), or articles like this, which talks about the history of the idea of entanglement more so than the properties and limits of entanglement. My interest is further stoked by the notion that entropy provides a measure of entanglement, and a 'connection between quantum information theory and thermodynamics' - a concept which I don't completely understand, but which I nevertheless now fantasize might be the missing link in this 5-dimensional model.
My questions are like a program that is always running in the background, consuming whatever spare resources can be found. They're not going away anytime soon. I know, I know - I should go study physics.
Until that happens though, you'll have the pleasure of listening to a cognitive psychologist butcher, twist, and mangle all of your cherished physics concepts. And it's not going to be pretty. If you're not tired of it already, you'll get there. I promise. :)
Sunday, March 1, 2009
Journal Club #7
"So, if we watch a recording of a soccer match played a long time ago, the outcome is undetermined, not just if we are watching the match for the first time and never read about the outcome, but perhaps also if we've seen the match before and forgot about the outcome." - S. Mitra, from arxiv version of an essay called Changing the Past by Forgetting submitted to FQXi The Nature of Time essay contest.
Alas, not the winning entry, or I would have been kicking myself... But Mitra did win the February arxiv.org quant-ph article-for-discussion contest that goes on in my head. (Congratulations.)
It was tough decision this month. Diosi's paper, titled Does wave function collapse cause gravity?, was a strong second, and lost out only due to the gaping coffee and math deficits in my tiny sector of the multiverse. (Sorry.) Inhabitants of other sectors of the multiverse are highly encouraged to read this paper, as wave function collapse (which establishes the definite state of an object - one might even say it is the state that corresponds to an object bearing a distinct identity) is linked to gravity, which I have previously speculated might have something to do with the neurophysics of economically seaming the represenations of distinct objects together.
But back to Mitra's essay...
You got me with the first line - "As pointed out by David Deutsch, it is possible to experimentally disprove all collapse interpretations of quantum mechanics if one could make measurements in a reversible way." An idea previously discussed by this author as well. But not something about which you can simply declare "Oh, I did that" and expect to be believed. ;)
What gets me about this paper is that the erasure of memory is discussed as a 'unitary operator that disentangles the observer from the spin.' Come again? Are we talking about a complete, or a partial, disentanglement? Heck, why are we jumping straight to entanglement/disentanglement analogies for memory/forgetting in the first place? I've been really careful to avoid leaping to entanglement as an explanation for anything other than observable entanglement behavior between two particles.
The author's use of a 'machine observer' provides an opening to discuss ideal memory erasure, which is presumably not a condition that can be easily found in human observers. My predisposition is to map 'forgetting' from our existing understanding of neurochemical and/or neuroelectrical dynamics in the human observer, and see how that maps onto reports of a changed past. That work could be extended into blocking memory encoding to prevent a permanent 'entanglement' with a particular outcome state. But I digress...
If I'm reading the paper correctly, the author suggests the use of memory resetting to a backup (prior) state as an escape from a forthcoming disaster. "The observer facing disaster can thus be almost sure to escape the disaster by doing a memory resetting." Interesting... I've escaped the 'disaster' of not finding the items I was looking for while shopping by 'forgetting' that I had just witnessed the absence of the desired item. Although I've never really thought of it as 'forgetting', but rather as a 'shifting of attention' until that observation was no longer in short-term memory.
It also follows then that we would want to be careful about what type of observations we make, as they may prove to be 'unforgettable', thereby "trapp[ing] us in the wrong sector of the multiverse." Sometimes a lack of information is a good thing - think of it as 'degrees of freedom' in your ability to select an outcome state. ;)
One final note - all of the essays on The Nature of Time can be viewed here, along with the number of popular votes they received. I'd like to meet the person who actually read all of those essays before voting. I'm just saying - that's a lot of essays...
Alas, not the winning entry, or I would have been kicking myself... But Mitra did win the February arxiv.org quant-ph article-for-discussion contest that goes on in my head. (Congratulations.)
It was tough decision this month. Diosi's paper, titled Does wave function collapse cause gravity?, was a strong second, and lost out only due to the gaping coffee and math deficits in my tiny sector of the multiverse. (Sorry.) Inhabitants of other sectors of the multiverse are highly encouraged to read this paper, as wave function collapse (which establishes the definite state of an object - one might even say it is the state that corresponds to an object bearing a distinct identity) is linked to gravity, which I have previously speculated might have something to do with the neurophysics of economically seaming the represenations of distinct objects together.
But back to Mitra's essay...
You got me with the first line - "As pointed out by David Deutsch, it is possible to experimentally disprove all collapse interpretations of quantum mechanics if one could make measurements in a reversible way." An idea previously discussed by this author as well. But not something about which you can simply declare "Oh, I did that" and expect to be believed. ;)
What gets me about this paper is that the erasure of memory is discussed as a 'unitary operator that disentangles the observer from the spin.' Come again? Are we talking about a complete, or a partial, disentanglement? Heck, why are we jumping straight to entanglement/disentanglement analogies for memory/forgetting in the first place? I've been really careful to avoid leaping to entanglement as an explanation for anything other than observable entanglement behavior between two particles.
The author's use of a 'machine observer' provides an opening to discuss ideal memory erasure, which is presumably not a condition that can be easily found in human observers. My predisposition is to map 'forgetting' from our existing understanding of neurochemical and/or neuroelectrical dynamics in the human observer, and see how that maps onto reports of a changed past. That work could be extended into blocking memory encoding to prevent a permanent 'entanglement' with a particular outcome state. But I digress...
If I'm reading the paper correctly, the author suggests the use of memory resetting to a backup (prior) state as an escape from a forthcoming disaster. "The observer facing disaster can thus be almost sure to escape the disaster by doing a memory resetting." Interesting... I've escaped the 'disaster' of not finding the items I was looking for while shopping by 'forgetting' that I had just witnessed the absence of the desired item. Although I've never really thought of it as 'forgetting', but rather as a 'shifting of attention' until that observation was no longer in short-term memory.
It also follows then that we would want to be careful about what type of observations we make, as they may prove to be 'unforgettable', thereby "trapp[ing] us in the wrong sector of the multiverse." Sometimes a lack of information is a good thing - think of it as 'degrees of freedom' in your ability to select an outcome state. ;)
One final note - all of the essays on The Nature of Time can be viewed here, along with the number of popular votes they received. I'd like to meet the person who actually read all of those essays before voting. I'm just saying - that's a lot of essays...
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