Wow, just today I read this:
http://physics.stackexchange.com/questions/10068/on-the-natu...
and I thought it was all explained quite simply and now this?
Quantum Entanglement Drives the Arrow of Time
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Re: Quantum Entanglement Drives the Arrow of Time
#12The reasoning sounds a bit iffy as in: “Finally, we can understand why a cup of coffee equilibrates in a room,” said Tony Short, a quantum physicist at Bristol. “Entanglement builds up between the state of the coffee cup and the state of the room.” I think you can understand coffee cooling quite well without any quantum stuff - the atoms in the coffee are moving faster than those in the room. There will be a tendency…
your claim is that the quantum physicist cited is making the analogy just to sound impressive?
Re: Quantum Entanglement Drives the Arrow of Time
#13 The rate of information increases.
Information wants to be free.
Only information explains its own existence.
The order and connection of ideas is the same as the order and connection of things.
The laws of information are laws about the dimensions of proportionality, which give the arrow of time an aspect of curvature (needing to exhaust a universe for exponentially narrowing arrows, so the onion-skinning of properties of a thing "come way may" at "frozen" temporal localities — what happens when we "bend" time at certain family resemblance (physical) properties?).
Re: Quantum Entanglement Drives the Arrow of Time
#14I thought it was the second law of thermodynamics that already explained the arrow of time? Well, that and friction?
Re: Quantum Entanglement Drives the Arrow of Time
#15Do we need entanglement to explain the Arrow of Time? Even though in classical mechanics, the past and the future are both equally observable, we remember the past and not the future because the future does not contain certain information yet -- the information to be introduced into the universe in the form of quantum fluctuations. One could even argue that all information in the universe was created at some point in time due to one quantum event or other.
I may have misunderstood though (I'm not a physicist). Entanglement does however, explain why systems tend to equilibrium rather than any other type of state as it evolves forward in time.
On a related note, I found this quote interesting. It reminds me of how HN comments about quantum information theory has a tendency to get downvoted:
> The idea, presented in his 1988 doctoral thesis, fell on deaf ears. When he submitted it to a journal, he was told that there was “no physics in this paper.” Quantum information theory “was profoundly unpopular” at the time, Lloyd said, and questions about time’s arrow “were for crackpots and Nobel laureates who have gone soft in the head.” he remembers one physicist telling him.
Re: Quantum Entanglement Drives the Arrow of Time
#16Seeing this article is rather bittersweet. I came to a similar conclusion in my college years but I never pursuit it further.
Taking Quantum Physics in college was a life changing experience and it reshaped how I viewed the world. I was always obsessed by time and one afternoon it became clear.
I explained my variation not as a cup of coffee but a handful of dice. Essentially every tick of time is rolling these dice. And the variation of dice from one combination to the next is the arrow of time.
Like one of the authors in this article, I got the most amount of resistance from physics major. For most part they had a dogmatic view of anything that they had not studied yet. If it wasn't in their books then it didn't exist.
I also came to the conclusion time travel as depicted in the movies will never happen. It can happen randomly in a smaller body but for anything large the arrow of time is almost impossible to reverse.
Re: Quantum Entanglement Drives the Arrow of Time
#17This was surprisingly beautiful. As a geek in programming/computers/information/mathematics, but only a physics admirer from afar, it is very suggestive, even natural, to explain the deepest physical reality in terms of information: "It was as though particles gradually lost their individual autonomy and became pawns of the collective state. Eventually, the correlations contained all the information, and the individu…
Makes me imagine anthropomorphized variables in a program having discovered the file system and the class definitions that they're instantiated from, but are still trying to figure out what RAM is...
Re: Quantum Entanglement Drives the Arrow of Time
#18This Google Talk https://www.youtube.com/watch?v=dEaecUuEqfc uses entanglement and quantum information theory in a clear and understandable way to explain 'spooky' quantum phenomena, like the quantum eraser, de-coherence, the aspect experiment, and the measurement problem. Even if you don't know any QM, just basic algebra and calculus, it's really approachable. I used to be a fan of the Many Worlds interpretation, bu…
I'm having a difficult time following his explanation. Here are a few of my stumbling points. Maybe you can help me out.
1) What does it mean that entangled particles are supercorrelated? How can S(A|B) = 2 or -1?
2) The formula for Von Neumann entropy is S = -Tr(p log(p)), where p is the density matrix. How do you take a log of a matrix?
3) Why does the interpretation rely on the density matrix? I've always thought of the density matrix as something that gives information about our ignorance rather than the system (this is why the density matrix mixes classical probabilities in alongside quantum amplitudes/probabilities - observer uncertainty is classical). Therefore, to me, any good interpretation of quantum mechanics ought to work without density matrices.
Unfortunately his paper here (http://www.flownet.com/ron/QM.pdf) doens't seem to have significantly more information than his talk.
Thanks for any help you can offer.
Re: Quantum Entanglement Drives the Arrow of Time
#19This Google Talk https://www.youtube.com/watch?v=dEaecUuEqfc uses entanglement and quantum information theory in a clear and understandable way to explain 'spooky' quantum phenomena, like the quantum eraser, de-coherence, the aspect experiment, and the measurement problem. Even if you don't know any QM, just basic algebra and calculus, it's really approachable. I used to be a fan of the Many Worlds interpretation, bu…
I'm having a difficult time following his explanation. Here are a few of my stumbling points. Maybe you can help me out. 1) What does it mean that entangled particles are supercorrelated? How can S(A|B) = 2 or -1? 2) The formula for Von Neumann entropy is S = -Tr(p log(p)), where p is the density matrix. How do you take a log of a matrix? 3) Why does the interpretation rely on the density matrix? I've always thought…
Didn't watch but,
1. Super-correlation is entanglement.
2. Tr (ρ log_2 ρ ) = Σ_k of λ_k log2 λ_k where λ_k is the k-th eigenvalue of ρ. Sometimes the log2 is instead ln.
3. Density matrix indicates degree of entanglement. You can measure L or R polarized light but you have an entanglement of the two. Mind you that detecting a bell state without loopholes has, to my knowledge, never been done. A systems density matrix for a system can be measured statistically (Quantum tomography?).
Re: Quantum Entanglement Drives the Arrow of Time
#20This Google Talk https://www.youtube.com/watch?v=dEaecUuEqfc uses entanglement and quantum information theory in a clear and understandable way to explain 'spooky' quantum phenomena, like the quantum eraser, de-coherence, the aspect experiment, and the measurement problem. Even if you don't know any QM, just basic algebra and calculus, it's really approachable. I used to be a fan of the Many Worlds interpretation, bu…
>I used to be a fan of the Many Worlds interpretation, but after seeing this, I'm now a big fan of the Quantum Information Theory explanation.
I know that both MWI and QIT interpret entanglement differently but I am not sure if I understand why one precludes the other (Your g+ post didn't help me much). Can you please point out exactly where the conflict lies, as they still seem compatible to me (perhaps with minor adjustments)?