Testing Quantum Entanglement...

Discussion in 'Physics & Math' started by Seattle, May 30, 2017.

  1. Nacho Registered Senior Member

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    I don't think they even have a "2 or 3 qubit" operational FULLY quantum computer. I'm certainly not aware of it.
     
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  3. arfa brane call me arf Valued Senior Member

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    IBM has their QX chip, and it's public domain--you can write your own programs on a 5-qubit computer.

    https://quantumexperience.ng.bluemix.net/qx/user-guide
     
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  5. danshawen Valued Senior Member

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    You have made me realize that it is going to be impossible to take entanglement completely apart and put it back together again without picking up 100 years of pieces of the wrong puzzle that have been crammed into some crazoid picture of quantum entanglement.

    So far, I haven't said anything about the EPR paradox, which basically seems to be the same issue of misunderstanding entanglement, so what about those wormholes?

    Here's the answer: NO wormholes. This is fantasy. There is no reason for wormholes to explain entanglement that could either be viewed as faster than light, OR ALTERNATIVELY, a part of a quantum field that is already entangled everywhere and shares the instant of time refered to as "now" everywhere in the known universe SIMULTANEOUSLY in every sense of that word.

    Let's start with an atom. A spin flip of a quantum entangled pair of electrons requires no transfer of bulk energy. If it helps you to visualize, go ahead and eliminate the requirement that fermions are not able to occupy the same 'space' at the same time. For all intents and purposes, THEY DO occupy identically the same space at the same time in the electron cloud of atomic structure.

    Now imagine a spin flip of such a superposed pair of entangled electrons that have probability density waveforms that are on top of each other, not in orbitals. That wasn't so hard to imagine, was it? Oh, yes, they can still both flip, and when one flips the other also flips instantly. It is the simultaneous pair of events that Minkowski could not allow because the speed of light was the basis of time for him, you see?

    This pair of quantum entangled electrons can likewise produce a pair of quantum entangled photons, and change energy state so that the photon is emitted and goes through a beam splitter which retains the quantum entanglement. Now we have a pair of quantum entangled electrons engaged in producing a pair of quantum entangled photons which have begun propagating as unbound energy.

    For the moment, forget about the laws of physics which govern the wavelength of the photon and pretend that the wavelength of this particular photon is going to be about 13 billion light years long. Got that? The photon is red shifted much further the longest wavelength possible to produce within atomic stucture, but forget about that too for the moment. There are other ways to make such a photon if necessary. It won't carry very much information in the channel, but here we are ONLY INTERESTED IN COMMUNICATING A SINGLE BIT.

    What happens, exactly, when the wave function of this system (2 entangled electrons, 2 entangled photons) undergoes a "collapse of its wave function? Let's say one of the two entangled photons is observed 13 billion light years from where it started its journey, one second after the Big Bang or whatever. No matter where in the universe you observe a photon, once it is observed, you may never observe it again, right? But its entangled twin will change state when you do that, no matter whether it is a few light femtoseconds from the atom that produced it, or 13 billion light years away. Why does it do that? BECAUSE THE WHOLE SYSTEM IS THE WAVE FUNCTION THAT COLLAPSED. Space in terms of light travel time doesn't matter once the photon reaches whereever it is observed, across the room or across the universe makes no difference. An electron or a photon has no concept of how big or small it is. To make a photon with a wavelength that long, perhaps all an electron needs to do is to expand to the size of the known universe. Ridiculous? NO, because I have just described the mechanics of an electron that is, for all intents and purposes, stationary. Now do you understand what is going on?

    It would make no difference to this thought experiment if the photons produced were in the visible, x-ray, or gamma portion of the electromagnetic spectrum. The number of cycles of whatever wavelength is irrelevant BECAUSE TIME IS NOT PROPORTIONAL TO THE SPEED OF LIGHT, and space is an artifact of time, not the other way around. Time is independent of space. The instant of "now" is independent of the rate at which time progresses, and time is also different for energy that is bound as opposed to a photon.

    I don't have the rest of the answers about quantum entanglement yet. I have only removed a few of the conceptual stumbling blocks. The entire theory needs to be recast to throw out Minkowsi's proportional division by zero to shoehorn time into a geometrical nightmare involving space.

    Now I can begin to answer some of your questions about quantum computing.

    Obviously, an extreme red shifted entangled photon will not be of very much use to the purposes of quantum computing. Are quantum entangled particles capable of carrying more than 1 qubit of information? How much information is 1 qubit, exactly?

    https://physics.stackexchange.com/q...f-states-and-required-info-for-bits-vs-qubits
     
    Last edited: Jun 2, 2017
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  7. arfa brane call me arf Valued Senior Member

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    In which case, nothing can be known about this "spin flip", right?
    Well, it was a little bit hard. I don't know what the distinction between being in orbitals and "on top of each other" means, for instance.
     
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  8. Nacho Registered Senior Member

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    I'll be darn! I wouldn't have believed they would get this far. I was worried that they were just over-hyping a simulator, but I can't find any articles challenging that the Q-experience really achieves true quantum computations.

    They show that they just put up a 15 (or was it 16) qubit processor to be tested out.

    Thanks for the link.
     
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  9. danshawen Valued Senior Member

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    Oh, it gets better. Dirac evidently came closest to describing the situation (electrons behaving like photons).

    http://www.spinograph.org/blog/what-heck-dirac-electron

    Dirac of course predicted the existence of the positron before one was observed experimentally (always impresses me).

    He also had a theory that every electron in the universe was really the same one because they all appeared identical in a quantum sense. Of course, electrons don't all have the same momentum or else an electron microscope wouldn't work the way it manifestly does. They are all identical in the quantum sense because the Higgs field is entangled, and provides electrons and quarks with their inertial mass, of course.

    Other charges can only increase the inertial mass of electrons (by accelerating them) in a single direction, rather like increasing the energy of a photon. Which is why electron microscopes work so well. Still believe that particle physicists understand what inertia really is, and that I don't? What kind of inertia could the Higgs mechanism impart to an electron that another electron or charge cannot?

    What kinds of problems could we solve if we could get data into our D-Wave qubits using an electron microscope? That idea sounds like a really easy way to superpose all sorts of intricate and complex data in a hurry. From, say, a diamond or something with a really regular structure like pure silicon.

    Materials science is a ready made market for quantum computing. Invest NOW.
     
    Last edited: Jun 2, 2017
  10. arfa brane call me arf Valued Senior Member

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    I like the way they describe a quantum algorithm as a score, and how the qubits are like notes, it's consistent with Einstein's idea that particles are like vibrating strings.
     
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  11. danshawen Valued Senior Member

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    Yes, that definitely fits the description.
     
  12. arfa brane call me arf Valued Senior Member

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    If it is a useful heuristic, then n qubits represent n different "notes". It isn't like classical strings where a single string vibrates in several harmonic modes simultaneously, n strings all do the same thing but n times.

    It's more like a set of n strings can only play one combination of notes simultaneously; n qubits as vibrating strings can "play" all possible combinations of notes simultaneously, exponentially more than any classical device.

    From the IBM site:

    "Superposition is strictly weaker than full parallelism, and strictly stronger than probabilism."

    What they mean there is that n qubits in superposition is not an actual array of parallel computations. But it is stronger than classical probabilism because of the exponentiality (over states in superposition).

    This is why quantum computers promise to be useful solving optimization kinds of problems--pattern searching, best path, etc.

    More: "Entanglement is a property of many quantum superpositions and does not have a classical analog. In an entangled state, the whole system can be described definitively, even though the parts cannot.
    Observing one of two entangled qubits causes it to behave randomly, but tells the observer exactly how the other qubit would act if observed in a similar manner. Entanglement involves a correlation between individually random behaviors of the two qubits, so it cannot be used to send a message.
    Some people call it “instantaneous action at a distance,” but this is a misnomer. There is no action, but rather correlation . . ."

    What can I say . . .
     
    Last edited: Jun 2, 2017
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  13. arfa brane call me arf Valued Senior Member

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    The operating specs and the schematic of the qx2 processor:

    Please Register or Log in to view the hidden image!


    Each qubit Q0 - Q4 has a specific frequency, and four more parameters. There's an extra Q-1 qubit, and a list of things labelled 'CR'. What does it all mean?
     
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  14. Fednis48 Registered Senior Member

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    1) There are a few techniques for verifying superposition, but at the most basic level, they essentially involve doing a simple quantum computation and verifying that you get the right output. Once you have a well-tested method for producing the initial superposition, then you don't check it at all; you just apply the method and then go straight on to your computation.

    2) Every quantum algorithm I know takes the form of: prepare some initial state -> perform unitary operations without measuring the system -> take a final measurement. So basically, the proper time to take the measurement is when the algorithm is done running.

    3)You're right that quantum computers require some classical post-processing. Some algorithms require post-processing more than others. But the total run time can still be much faster than a purely classical computer; think a few minutes of quantum processing followed by a few seconds of classical analysis to solve a problem that would take centuries on a modern supercomputer.
     
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  15. Write4U Valued Senior Member

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    Question;
    Can a particle inside an atom be entangled with a particle inside another atom or can entanglement exist only between two "free" particles?
     
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  16. Seattle Valued Senior Member

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    Two atoms can be entangled.
     
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  17. danshawen Valued Senior Member

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    Yes. A superconductor Cooper pair is an example of this.
     
  18. danshawen Valued Senior Member

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    Yes. This is easier to accomplish in a Bose-Einstein condensate, but liquid Helium is another example.

    Diatomic or triatomic gasses would be another example, but these are small clusters of condensate and have few really useful applications in terms of quantum computation.
     
  19. Write4U Valued Senior Member

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    Ahhh, thank you all, perhaps that already answers my next question, but I'll do a little research first, on forms of entanglement, so that I can pose my next question coherently.
     
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  20. Nacho Registered Senior Member

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