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Quantum entanglement in time

  1. Jan 9, 2008 #1
    Hi everybody...I am new to the forum and I hope I am posting this to the right area.
    I am not a physicts but it is one of my favorites and I have been reading -particularly quantum mechanics - for over ten years from various sources. Anyhow, I am curious what you guys think regarding below thought exercise...appreciate if you let me know whether my logic has flow in it or not.

    I was thinking about quantum entanglement. What bothers me is that if everything has started/produced from a single source (i.e.big bang) then everything has to be connected to each other to some degree. But we do not see any evidence for such connection. If every particle is entangled with the rest then every experience I have must be connected to your experience. But this is not happening.

    So, what about this:
    Right after the creation, all particles distributed along the space time geometry - not only in space but in time as well. In that case, particles might be entgangled in time but not in space. Put it this way: The book I am reading at time T is entangled with the book at time T+1. But the key point is, the book at T+1 is not the same book at time T. Yes, they look similiar in every aspect but not even one single atom in it is the same. The reason that book(T) does exactly look like the book(T+1) is because the particles in book(T) are entangled with the ones in book(T+1). This idea resembles discrete time view.
    The space and everything in it at this moment is at its collapsed form. And future has all the particles which are still at their superposition but entangled with the particles in this very moment and eventually they will collapse and in that case they will turn into the particles that they were connected to.

    According to this thought, space is construct that includes collapsed particles and time is the construct that includes entangled particles at their superposition. But due to entanglement, decoherence will take place and time will turn into space (when all these particles collapse).

    Note that entanglement takes place instantenously. Therefore, particles at time T will cause their entangled particles collapse at T+1 instantenously, and T+1 will cause collapse at T+2, and so on so forth. In that case, everything has already collapsed so all we have is an already built construct. Our experience of time flow is a different issue tho. My argument is: we are flowing in this construct with speed of light (after the collapse things become governed by classical mechanics) and therefore we are not moving in the construct instantenously but at a lower speed (speed of light)...this lag is the reason for the time flow perception.


    If every particles in space at the begining are entangled with the ones in time then why do we have any "change" or variation or different things at all?
    If everything is entangled the way I described above then there must be one steady picture all the way in spacetime and there shouldn't be any variations in time?

    Simply put it this way, why this second is not exactly the same as next second? Meteors are moving, matters depreciate etc...

    Don't want to go any further but the change is due to (i) radioactive decay (ii) variation in forces due to their different position/coordinates in their time-space reference (iii) freewill (I know that sounds cozy but without this, there is a huge gap...)

    Please go easy on me...I am just curious and respect your knowledge and profession. Only you guys can help me out...

    Thanks in advance...
     
  2. jcsd
  3. Jan 9, 2008 #2

    olgranpappy

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    what is your support for those previous four statements?

     
  4. Jan 9, 2008 #3
    No support...I don't think there is any experiments done regarding time entanglement. So this is more like a philosophical discussion. But here is what I seek here.
    There is no way someone can prove this thought experiment but if there is a big flaw in my logic then you can certainly disprove it. Basically, I am asking your wisdom to take this idea down with solid- already proven- facts!
     
  5. Jan 9, 2008 #4
    "The book I am reading at time T is entangled with the book at time T+1."

    By this logic of everything being connected at the very beginning, why wouldn't book at time T not be connected with everything -- not just book at T+1, but your loose shoelace at T+2 as well as the shoelace at T? Seriously, this is not a joke.
     
  6. Jan 9, 2008 #5
    How do you know it's not happening? The wave function describing every possible state of the universe would naturally include every particle in the universe. So everything IS entangled with everything else. But the entanglement is so weak because the universe is so big that it is undetectable. Nevertheless, I suspect that one could prove that if you could somehow determine the wave function of every particle throughout its entire history from the moment of the big bang, you'd find the state of some particle in the Andromeda galaxy at this moment has an infinitessimally small correlation to the state of a particle on Earth. The eigenvalue would be something on the order of 1 divided by the number of quanta in the universe, but it would not be zero.

    It's similar to how we are breathing molecules that were once in the body of Julius Caesar. We might not perceive it but statistically we know it must be true.

    I wonder if there is a formal paper on this. I'd love to read it if so.

    As for the rest of your post, I don't know what time entanglement means. All the experiments I know of entangle either momentum, spin, or position. You could also entangle charge, mass, or anything else that has to be "conserved."

    There are plenty of theories and interpretations as to what "time" actually "is" but I don't think anyone really knows why we are moving in it or why the state of things is changing.

    However, I do believe that solving the mystery of entanglement will open up a dramatic new branch of understanding just as the discovery of quanta itself did 100 years ago.
     
  7. Jan 9, 2008 #6
    If the value is not zero, then there would be a theoretical connection (although infintesimally small) to particle A on Earth and particle B in Andromeda. Perhaps even with atomic computers it would simply take more processing power than there are atoms in the universe to compute this.
     
  8. Jan 10, 2008 #7

    ZapperZ

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    The flaw here is that you did not understand the property of quantum entanglement.

    What is entangled is the observable of the system. An observable in QM is represented typically by a Hermitian operator, and the system being entangled typically will produce an eigenvalue of the system. This may not mean much to you, but those are the mathematical rules that govern this phenomena, and in QM, the mathematics came first before the "words" and interpretation.

    So in your scenario, what is the "observable" that is being entangled? "Time", in QM, doesn't quite qualify as an "observable". When you start with a faulty premise, there's very little rational explanation one can produce to account for the "outcome", since the starting point isn't valid.

    Zz.
     
  9. Jan 11, 2008 #8

    Hi ZapperZ...

    Thank you very much for your feedback...

    First I must say, I agree that mathematics is the key. Therefore, my lack of mathematics in quantum mechanics is a serious limitation. That is why I am seeking professional help here.

    You are refering to "observable system"... There should be a measurement in the system so that collapse can happen. To my knowledge there are 3 ways to collapse wave form (i) measurement - as you suggested (ii) environmental entanglement (iii) Self-collapse -due to quantum gravity (Penrose and Hameroff).

    See, what I am suggesting doesn't require a continous measurement in time. Once a quantum wave is collapsed due to any one of the 3 items above at time T then it would collapse the rest of the system (T+1,T+2, T+3, etc...) instantenously. They are entangled.
    Again, any wave that takes a certain position will instantenously collapse its entangled particles in time. So you do not need to observe the system in every moment -only one time observation at any moment in time (or self collapse at any moment in time) is sufficient.
    In short, there is still an observer and observed (in particular moment)- sorry but I don't see any violation here...

    So please let me know what you think...
     
  10. Jan 11, 2008 #9
    Hi Peter,

    I was expecting this question...Thanks for giving me the chance to explain.

    The one thing that really bothers me is this: I understand the whole universe is full of so many particles (who knows may be it is not - may be everything is just one electron but lets assume it is) and this make us think that the entanglement is weak but it is still there.

    I disagree with this. If everything is entangled then there should be no particles at their superposition, don't you think so? Yes, the perfect correlation between entangled particle A and B is not as clear because of the amount of particles entangled but everything should at least assume a certain state (or collapsed). Since at least one of them is observed then the rest should assume some form of certainity and there should be no such thing as superposition. But it is there. That suggests me there is no entanglement in space (unless we create it in lab artificially).

    But think for a second that entangled particles are distributed along the time dimension. Then the entanglement is evident. Everything in this second looks alike the next second.

    So allow me explain further:
    Assume at time T, you are observing a wave particles at its superposition. You sent photons by looking at the wave form particle and you cause it collapse. From photons perspective, there is no time passed and the collapse happen instantenously. From your point of reference you cannot stay at time T EVER. So you have already come to T+1. When you look at the collapsed particle at T+1 you will see the particle but this process happened at T and you are already at T+1. How come, you can observe something that has happened in the past - you cannot because - correct me if I am wrong - collapsed particles (say electron) cannot travel in time so information is kept at time T and cannot move to T+1. So you and the electron observed are at two different coordinates.

    Now, what I am suggesting is this: You never see the same electron that is collapsed at T but you see it entangled electron at T+1. When you collapsed the original electron at T, this instantenously collapsed its entangled particle at T+1. You think you see the same electron, but you do not.

    That is how I imagine quantum entanglement in time...

    Looking forward to your counter argument...
     
  11. Jan 11, 2008 #10
    Hi Bullwinkle, please see my response to Peter...
     
  12. Jan 11, 2008 #11

    ZapperZ

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    This doesn't make much sense. What is "collapsing", and what observable is being measured? That is something you have not clarified.

    In the standard EPR-type experiment, for a bipartite system, it is the spin state that is the "observable" that is being measured. 2 particles are entangled via the spin state, i.e.

    [tex]|\Psi> = |Up_1, Down_2> + |Down_2, Up_1>[/itex]

    The two spin states are said to be "entangled" based on that mathematics. And the spin (or the spin projection) is the observable.

    What is the observable of your "time entanglement"?

    Zz.
     
    Last edited: Jan 11, 2008
  13. Jan 11, 2008 #12
    The very act of observing it destroys it. "Observing" an electron means it gets absorbed and manhandled by the atoms in the detector. It immediately becomes indistinguishable from the others. So it's impossible to "observe" an electron at T=0 and then observe "the same one" at T=1. You can't simply observe it's path through time.

    Similar with photons. You can "observe" the photon strike a detector. It's then gone. There's a _record_ of it in the fact that a current is generated in a detector that eventually travels to a coincidence circuit which uses a computer to record the data.

    Do you want to ask whether the physical manifestation of the information, i.e., an atom in the detector or in the coincidence circuit, is subsequently "entangled" with the original photon?

    Take a laser beam through a double slit (S0 and S1) followed by two "which-slit" detectors D0 and D1.

    |Psi> = 1/sqrt(2)*[|S0,D0>+|S1,D1>]

    Your argument is that the photon is entangled with the two detectors, right?

    I can see the temptation to say this. The detectors carry information about what the photon did, and observing either detector tells you which slit the photon passed through, just as surely as observing one entangled particle tells you something about the other.

    BUT the difference with normal entanglement is that the connection goes only one way - into the past. I can only observe D0 or D1 to learn about what happened at S0 or S1; I cannot observe the photon to learn which detector it will hit without _influencing_ which detector it will hit. In normal entanglement, I could observe either end to get info about the other; here I cannot do that. The reason for that is the uncertainty principle.

    So I would argue that the uncertainty principle prohibits you from saying that something that happens at T=0 is _entangled_ with something that happens at T=1 because you can't know what happened before T=1 without influencing what happens at T=1. It turns out that this same principle applies to truly entangled particles! Meaning I can't observe one member of an entangled pair without influencing what the other will do! Hence, if I detect which slit one member of a pair passes through, I never see the interference pattern in the other, and therefore I can't predict the future behavior of the other because I just influenced it.

    The other half, I think, of what you're arguing is more applicable to the macro world. Say I see a car going by me at 10 m/s. If I observe the car at t=0, x=0, and then again at t=1, x=10, I am pretty certain I'll see it at t=2, x=20. But that is not entanglement. There are *so* many variables going on all around me, that it is utterly impossible to analyze the situation with a wavefunction. Countless things influence the probability of seeing the car at t=2,x=20 (it's by no means guaranteed) such that the probability distribution would always be normal, witt x=2,x=20 obviously having the highest probability. But, the correlation would actually be much stronger if there were really entanglement occurring. I don't know if anyone's tested the Bell inequalities on macro objects (or if one could) but I am certain they would not be violated.

    It's when we isolate the system down to individual particles where the external influences become negligible enough that we can see the effects of true quantum phenomena. Unfortunately, that's exactly where the uncertainty principle starts to prohibit us from learning enough information about the present to make predictions about the future!

    Sometimes it feels like nature is conpsiring against us to preserve the order of time.
     
    Last edited: Jan 11, 2008
  14. Jan 11, 2008 #13
    Hi Peter...I enjoy reading your post and I agree with all the points you made...The thing is quantum entanglement in time doesn't contradict with any of the arguments you made- as far as I can tell. So let me comment:


    What I am saying is that you cannot observe the same particles at T=0 and T=1. So that doesn't contradict with your argument, in fact it gives another explanation.
    The electron you observe at T=0 influence the other entangled pair electron at T=1 and you can only see the entangled one at T=1. You are measuring the electron T0 which instantenously impact the one at T1 and you can only observe the entangled T1 electron. The one that you originally measure was left at T0. So I am not observing T0 electron's path I am observing another electron entangled with T0 electron..

    Okey so here is the most important part. I think I wasn't doing a good job explaining this.


    You are saying: "something that happens at T=0 is _entangled_ with something that happens at T=1 "

    Exactly...

    But I wasn't suggesting that something happens at T0 is entangled with SOMETHING that happens at T1. It is not important if 2 things happening at different times. What matters is the initial event-measurement- at certain moment in time,T0. When I observe any quanta particle at T=0 then that is it. Its entangled pairs will immediately assume the same form and when I observe the entangled pairs going forward at T1, T2, T3,....TN, it doesn't matter anymore.

    Lets forget about time entanglement for a second. So in EPR experiment, you measure one of the entangled particles, lets say particle A. So you influenced it and hence you influenced its pair B. B reacted instantenously to your observation on particle A.
    Due to the phenomenon of superposition, the measured particle has no single spin direction before being measured but once it is measured its pair in opposite direction would have the exactly correlated spin direction.

    Now, after measuring A, if I go and look at particle B this time, does it matter? No....Because you have already collapsed the system therefore A and B assumed the certain state.

    Please now reverse space with time. Instead of space, assume EPR took place in time? Remember, what I am suggesting is that wave particles are distributed not only in space but in time as well...A is one particle at T0 and B is another one at T1. If you measure A at T0 then eventually B at T1 will react instantenously. When you move to T1 and look at B, does it matter? Again, the answer should be no...

    So as you say, once you measure it, you won't see an interference pattern. Therefore, any WAVE that is being measured at any time,T0, will always stay as PARTICLE going forward, T1+.

    As I said in my initial post: "Space is the construct of collapsed particles and time is the construct of entangled particles at their superposition".

    So I don't really see the contradiction yet...With all due respect,what you explain is very consistent with this.


    -----------------

    I have always thought time as a construct that have particles in it even before I develop interest to quantum physics. I thought we are flowing within those particles. But then I always wonder, why everything this second resembles with everything the next second. I see the chair and the chair is there after one hour. So I won't be able to find an explanation. When I start reading about entanglement, I immediately make this link. They are the same because they are entangled in time.

    We are making the mistake of interpreting things only in space, yet we should interpret them in time because we can stop our motion in space but not in time. Every experiment -from our reference - takes place in time yet we constantly ignore "the time" in our interpretations.
    -----------------

    As I mentioned earlier, if you collapse a wave into a particle by observing it, then there are two things happening. One you collapse the system and second you watch the outcome.

    When you collapse the system, the outcome is not available to you because you left it in the past. But our experience tells us the opposite. I collapse the electron wave function and then I watch the particle electron. The first takes place at T0, and the second one takes place at T1. It can't be....

    Unless....

    Example:

    Space
    |
    |
    |
    |W
    |A
    |V PARTICLE PARTICLE
    |E
    |
    -----------------------------------Time
    T0 T1 T2


    Assume at T0, you measure wave electron. Electron collapsed but it cannot move to T1.
    But you move to T1 (because you cannot stop time and you are flowing in it). Since electron cannot follow you to T1, you shouldn't be able to see it at T1. But you can...
    When you are at T1, you watch the electron particle. It cannot possibly follow you, can it?
    So what is this particle that you are seeing at T1?

    It is the entangled particle....


    BEFORE THE MEASUREMENT

    Space
    | ... E
    | ... N
    | ... T
    | ... E
    | ... N
    | ... G
    | ... .
    |W ... W
    |A ... A
    .|V ... V
    |E ... E
    |
    -----------------------------------Time
    T0 ..... T1
    yourhere


    WHEN YOU MEASURE IT:
    1-YOU MEASURE IT AT T0 and WAVE -> PARTICLE
    2-BUT IT ALSO CAUSE ENTANG.WAVE-->PARTICLE (instantenously)
    3- YOU MOVE TO T1
    4- PARTICLE (i.e. electron) stays still at T0 (it cannot move thru time)
    5- YOU ONLY SEE ENTANGLED PARTICLE

    Space
    |
    |
    |
    |
    |
    |P ... P
    |A ... A
    |R ... R
    |T ... T
    |I ... I
    |C ... C
    |L ... L
    |E ... E
    -----------------------------------Time
    T0 ... T1
    ... youarehere


    Does it make sense?
     
    Last edited: Jan 11, 2008
  15. Jan 11, 2008 #14
    Oh now I see what you are asking...
    I know I am confusing you, my apologies...

    The difference between space and time in my thought experiment is , the first is the set of collapsed particles and the second is the set of entangled particles (with set 1) at their superposition.


    In the EPR experiement,particle A is entangled with particle B and when you measure A, it instantenously influence B regardless of the distance between them.
    What I am suggesting is...
    What if (there is a BIG what if here) time is a construct just like space but only full of entangled particles (entangled with the particles in the past). When you think of each moment as a slice of bread then each slice has its own particles in it. The second slice is entangled with the first, the third with the second etc.
    In that case, time is causing confusion.

    Take EPR experiment, rather than thinking particle A in USA and Particle B in Australia, assume that A is in this moment and B is in the next moment.

    Then "observer-observable" doesn't change at all. The only thing that changes is the dimension that it took place. Basically, I am suggesting to replace space with time and also just like space is full of particles (particle form), I am suggesting time is also full of particles (superposition form). And particles in each time slice is correlated with the particles in the next time slice. But there is no change in observer-observable setup...

    Too abstract???
     
    Last edited: Jan 11, 2008
  16. Jan 12, 2008 #15

    ZapperZ

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    But you still haven't told me WHAT is being entangled!

    Notice that from the bipartite entangled wavefunction that I constructed, it doesn't restrict one from measuring the two properties either separated in space or in time. So what's the big deal here of measuring the entangled property LATER?

    You should also read our PF Guidelines, because I see this going off in an unjustified, speculative area. While we certainly welcome questions on something that people don't quite understand, after several queries from me, it appears that this is going off into a direction that is filled with vague usage of physics terminologies and speculative guesses. I think there many things that you do not understand about entanglement (and QM). You need to know that FIRST before you try to use it.

    Zz.
     
  17. Jan 13, 2008 #16
    Hi Zz...

    Thanks for your comment...I understand this discussion becomes so speculative and it defeats the purpose of the forum. I won't continue posting under this thread.

    But also letme say this: Some people like myself do not have the proper academic background in physics and we built our knowledge in a non systematic way and sometimes acquired thru uncreedible sources. Unfortunately, I do not know anyone with physics major who can help me out and forums like this are my only opportunity to get enlightened about the issues I am trying to deal with.

    But rules are rules so I respect. I would like to ask one big favor tho.
    Is there anyway that you can pass me your contact email to my private message (or any of you who is reading this and want to help)...Because I still believe I couldn't express my idea well. It is partly because it is difficult to present it in the basic test form. If I can get one of your email then I can send you a better word document with figures etc.
    If I cannot get any help from one of you then I am stuck...hope one of you can help me out.

    Thnx
     
  18. Jan 13, 2008 #17
    I enjoy reading the discussions here. I think the debate is not only good for the aspiring novice, but also the trained physicist as it may help her rethink and solidify her ideas.
     
  19. Jan 14, 2008 #18
    Feelalive, I think what you're trying to do is posit a possible interpretation of what quantized time might be. It is indeed pretty speculative. :) I for one think these discussions have value as long as people reading it aren't led to believe it's anything more than speculation. But, according to the rules here that sort of thing is frowned upon. :(

    But maybe I can put a non-speculative spin on the discussion. Are there any published papers on entanglement between time separated quanta?

    I will also add that any time you reflect a photon off of a mirror or a beam-splitter, you are creating a "new" photon at a "later" time, which has the same momentum and polarization (but different phase) as the previous one. The wavefunction of the two photons looks a heck of a lot like the wave function of two photons that were created simultaneously in an entangled state - if they didn't, it would be impossible to use beam splitters and mirrors in these experiments! Is it accurate to say that photon A is "time entangled" with photon A' which is the reflected photon? I don't know...
     
  20. Jan 15, 2008 #19
    Hi Peter...thanks very good suggestion. I have been searching for any articles written on timelike entaglement but I wasn't able to find even one. I have access to some of the physics ejournals and no results came up.

    However, I found one interesting article regarding conscioussness which is called: TGD inspired theory of consciousness by Matti Pitkänen (looks like a popular one). This article uses timelike entanglement as a big assumption to build their cases.
    It doesn't discuss much about the timelike entanglement so I am not sure how they construct it -instead they take entanglement in time as granted.

    It surprises me how they use timelike entanglement to explain physocological timeflow.
    If I understood correctly, there is an argument such that timelike entanglement explains recognition and consistency in our experiences as well as memory. And spacelike entanglement (as in EPR experiment) explains decision making and information processing within the brain...when you think about it, it makes sense...

    I read all articles written by Hameroff and Penrose re: quantum consciousness but this one is certainly more provoking. I am still researching....

    Correct me if I am wrong but once a photon A hits the surface, it is emitted by electrons and that photon A is completely gone. The bouncing photon (B) is another one that has the same wave function. That is my understanding.
    So, in a timelike entanglement, photon A still correlated with Photon B only in a different timeframe. This is actually a very good question. I am still thinking about this. But I prefer not to discuss to avoid speculation...
     
  21. Jan 16, 2008 #20

    ZapperZ

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    Please do not use such sources, or bring it up in here. Such unverified bastardization of QM is not allowed on here. Again, please review the PF Guidelines before using such sources.

    Zz.
     
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