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Entanglement thoughts

  1. Sep 14, 2010 #1
    Hello, I'm new to the community here at Physics Forums. I am an undergrad double majoring in mathematics/computer science. I will soon be enrolled in a double masters for both math and comp sci...and eventually would like to enroll in a physics PhD program. Well then, enough about me...here are my thoughts.

    From what ive researched on quantum entanglement it seems that the pair of electrons or particles entangled will be instantly changing spin according to its entangled partner. Now, the idea of sending information by the entangled particles has been refuted it seems by much of the academic community. It seems as though people suggest that no information is sent, rather the communication between the particles is instant...few suggest that IF there is information being sent, it must be traveling over 10,000 times faster than light.

    Now, to the point...does it even matter if quantum entanglement is sending information or not? Let me give an example:

    Lets say two photons are entangled. One is in New York and the other in LA. Now, regardless if any information is being sent between the particles, could we not just utilize the 'spin' of the electrons to communicate with servers? For instance, a spin will be 'up' or 'down'. Well, in binary (machine language) the options that a computer understands is either 0 or 1. So could we not just find arbitrary points in time and say one electron spin is up while its entangle partner's spin is down...and have the computer understand this? Thus, sending information instantly or perhaps to some, 10,000 times faster than light. One could write an operating system that understood this, thus revolutionizing information being sent by large distances, and more efficiently. Please, give me your thoughts.
     
  2. jcsd
  3. Sep 14, 2010 #2
    Oh, one last thing, to make it more practical of an idea, one could control the spins using magnetism no? Thus, when changing the spin of one, you have changed the spin of the other, and when this happens, you have successfully communicated from New York to LA, assuming there is a way to make a computer understand the spins.
     
  4. Sep 15, 2010 #3

    DrChinese

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    Welcome to PhysicsForums, NetMage!

    My I ask how you intend to set the bit as up or down?

    The point being that changing one does NOT change the other instantaneously. OBSERVING one tells you the value of the other instantly, but that is simply redundant information.
     
  5. Sep 15, 2010 #4
    Well, I have not gotten that far yet :) However, it simply seems as though this idea is feasible, and I will continue to put thoughts toward it as I further myself into my academic endeavors. I think we will find that this can and will be done.
     
  6. Sep 16, 2010 #5
    It's pretty established that information does not travel faster than light.
     
  7. Sep 16, 2010 #6

    JK423

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    Here you dont care about "information sending" via entanglement, but below your idea is based on information sending
    This idea is all about information sending and this is shown to be impossible. Check other similar threads for the *why*
     
  8. Sep 16, 2010 #7
    Hm, I think you may be misreading what I was trying to say. What I'm trying to convey here is that regardless of there actually being any signal or 'information being sent from one entangled particle to the next', we can know one thing about each particle. If one is spin up, then the other is spin down. That seems like all the information WE need in order to establish communications. Dr.Chinese raised the best question, how will we organize the bit for the computers that are to interact with the spins. I am by no means claiming to be an expert here, it just seems as though we are overlooking perhaps a few things when deriving meaning from quantum entanglement (ive only read a book and a few lecture series over it). An interesting question is, if we observe the spin of an entangled particle, we know the sping of its counterpart...as Dr.Chinese stated, redundant information. However, perhaps what we need to be working on first in order to begin thinking of organizing the bit or other methods of communication, we must first find if there perhaps is a way to control spins in entangled particles. It is a relatively new phenomena that we poorly understand.
     
  9. Sep 16, 2010 #8
    I just want to be sure here: you understand that without classical means (read: lightspeed or less) you can't communicate INFORMATION that the other party will understand? You are still limited to light or sub-light communication with this method, even if the spin-flip occurs at 10,000x or more c?
     
  10. Sep 16, 2010 #9

    DrChinese

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    The phenomena of entanglement was named as such circa 1935. So if you call 75 years old "new", then I would agree with you. It is true that the technology to readily entangle particles is only about 20 years old - that being Parametric Down Conversion. However, there is a lot of theory going back further than that.

    The theoretical issues surrounding entanglement are better understood than you may have been led to believe. There have been perhaps 20,000 papers written on the subject including probably 5000+ different experiments.

    In general, there are 2 elements needed for entanglement: a) some kind of conserved system (such as total spin or momentum); and b) 2 or more particles in some kind of superposition of states. Using quantum mechanics, it is possible to predict and test a variety of exotic effects. To date, nothing has been seen which is not consistent with the predictions of QM. That includes delayed choice experiments, quantum erasers, as well as the kinds of seemingly non-local behavior you cite.

    There is absolutely nothing in all of this that has ever given a hint that superluminal (FTL) communication is possible. You may as well speculate that warp drives are possible too. Not meaning to sound sarcastic, I am simply pointing out that there is no science behind your idea. I encourage you to ask questions and read more about this fascinating subject. :smile:
     
    Last edited: Sep 16, 2010
  11. Sep 16, 2010 #10
    Well, before I got on, help me better understand this, as I stated, I'm no expert, just an undergrad about to go to grad school. I just have extraordinary interests in subjects such as these, hence why I plan to extend my grad studies after my math and CS dual masters program, into a physics grad program. Now, if there are two entangled particles, and we know the spin of one, that tells us information about the other as I understand. If we KNOW (which we would not have to, because you could just pick and arbitrary point and time and call it up or down) the spin of one particle, we KNOW things about the entangled partner. In an abstract way, information has already been sent. Maybe not through the particles themselves, but information through us. Because we know one, we know the other, so not necessarily sending information, but hopefully you understand what I'm getting at. Now as far as communicating information faster than light, you are misunderstanding my intentions. In my first post I stated that for reasons I'm trying to get across, there doesnt have to be any information being sent. Let me reinvent my scenario and try to better explain myself and you may critique it as necessary.

    Ok, So we have two entangled particles, one lets say in New York, and one lets say in LA. Now, ASSUMING (and here is where it is all hypothetical and the main point of this thread) *we can figure out how to control the spins on the electrons*, for my elementary brains purpose, I will say magnetism. Using magnetism, the servers only have to know when the magnets change to communicate. Spin up = 0 lets say, and spin down = 1. you could design around this idea. And yes, I understand this is hypothetical and was hoping maybe someone could fill me in if i am misrepresenting the phenomena of entanglement.
     
  12. Sep 16, 2010 #11
    Thank you Dr.Chinese for your hospitality :)
     
  13. Sep 16, 2010 #12

    JK423

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    That's the point! We cant control their spins. When you make a measurement on your electron's spin, the outcome is random! If we could control the outcome, then yes we would be able to send information instantly. The fact that we cant makes it impossible.
    For example, say that '1' is spin up and '0' spin down. In order to send the message 100111101 etc you should be able to control which value the spin would take, and that's determinism. Quantum mechanics do not allow this. So, you would send something like 100111010101, but i wouldn't mean anything because it would be just random bits with no meaning.
     
  14. Sep 16, 2010 #13

    DevilsAvocado

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    I don’t wanna tear down any "newborn interest", but there is one crucial fact about entanglement that you’ve seems to have missed. Yes, if we arrange the measuring equipment in a certain way (aligned parallel) then a "YES" (or 1) at one site will certainly be "NO" (or 0) at the other site.

    But there is no way to force one of two states out of a QM system with a 50% probability! If it was, there would not be any QM probability, which is the very basis of QM. Most of today’s technology with computers and cell phones and other cool gadgets all build on the fact that QM is correct.

    Let’s say you want to send the letter "A" from New York to LA with entanglement. Letter "A" in binary (computer) format is:
    100 0001​

    How are you going to control this so this is the sequence that is measured in LA? There are 128 combinations in 7 binary digits, and the receiver in LA might just get any random binary value:
    101 0101​

    This is translated to the letter "U". Sure, in LA they will know that New York now will have:
    010 1010​

    But this is translated to the character "*", and this is not much of a meaningful 'conversation', right? :wink:

    This just doesn’t work...


    EDIT: Oops, JK423 is basically saying the same thing... :smile:
     
    Last edited: Sep 16, 2010
  15. Sep 16, 2010 #14
    I see, interesting indeed
     
  16. Sep 16, 2010 #15
    Now, see there...we have already made some progress. We went from quantum entanglement not being able to send information...to sending meaningless information...just because it hasnt been done, does not mean it cannot. I'm no physicist yet, however I do believe there is so much we dont know. And in the span of a few comments on a thread we have figured 1 thing out.
     
  17. Sep 16, 2010 #16
    No one has "figured" anything out in this thread, what we have are people explaining the basics of QM probability distributions and the need for classical means of verification using entangled pairs. Lets get be grandiose about this... there are at least half a dozen threads like this which you could read and have your questions answered.

    To be brief: the speed of light in vacuum (c) is the limit for communication... when you start to suggest that people establish codes ahead of time, we'll point out that as "Alice" and "Bob" have to travel sub-c, then communicate, you're just changing the order of when the classical means are inserted.

    I could go on...
     
  18. Sep 17, 2010 #17
    Would someone go into more depth as to WHY we cannot control the spins on the particles? As I am understanding this, we CAN infact know the spin of a particle and thus determine the spin of the other...? Or am I once again misunderstanding? It seems to me if one had several entangled particles, enough to ALREADY set up the bit, then there would be no problem with this, regardless of changing spin. For instance, say we have enough entangled particles in a system that essentially codes for binary. I understand this will be millions or more different combinations. But SAY we have this established (Once again I understand this is not very practical, more about the principal), would this not allow for communication? To repeat myself: Say we have millions of, or whatever arbitrary number it would take, entangled particles to set up the combinations for lets say...basic text...the binary...without even having to change spins, is this still not feasible. From everything that has been explained and that I have researched...this does not violate any QM.
     
  19. Sep 17, 2010 #18
    You CAN communicate information using quantum methods, you just can't do it faster than c. The principle you've articulated is behind the hopes for a quantum computer in many ways, without the emphasis on speed at least. Once you say, "we have this established", you require that two or more people be in CLASSICAL communication (face to face, radio, or other) to set the ground rules for each change of state. You're not really using the entangled pairs to send the information then, but rather as a way of securing information over great distances, or a means of signaling... still the information itself propagates at c or slower.
     
  20. Sep 17, 2010 #19
    nismaratwork, I am not simply asking a question. I am getting to know the scientific community better, learning, and hopefully if not now, soon be contributing to it. This just so happens to be a topic of interest, and that as I learn more about it, may perhaps do research in it and write my dissertation on. I'm 20 years old, and far ahead of most of my peers. Cut me some slack ;)
     
  21. Sep 17, 2010 #20
    Right, I understand this. I just wanted to establish whether or not entanglement communications is a feasible method. thats all haha.
     
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