Entanglement Definition and 882 Threads

  1. T

    Trying to understand Quantum Entanglement, String Theory, and the BB

    Consider me physics illiterate since my last class was advanced placement physics in high school (over 20 years ago). I am trying to understand what the title says, How does quantum entanglement, string theory, and the BB fit together? Skipping to the meat of the subject, everything revolves...
  2. DrChinese

    Entanglement Between Photons that have Never Coexisted

    I have posted many times that entanglement between photons that have never existed at the same time is theoretically possible under QM. Now an experiment has been performed that demonstrates this. The technique uses entanglement swapping. Photons 1 and 2 are created as an entangled pair...
  3. G

    How Can the Bell Experiment Be Performed with a Guaranteed Polarization?

    Say you have two cards: an ace of spade and a king of spades. You put one in your hand without looking at it, then you travel 10 km away. You look at the card, it's an ace of spades and you know instantaneously that the other card 10 km away is a king of spades. Information has just traveled...
  4. L

    Quantum Entanglement at the Big Bang

    Because the universe started as a point of almost infinite density, wouldn't that mean that every particle in the universe interacted with one another while in that state, crammed together, thereby causing all the particles in the universe to be entangled, including those particles that created...
  5. S

    Is single particle interference explainable via entanglement?

    Do you think that: Single particle interference is explainable via entanglement? For example: in the single particle double slit experiment
  6. Ookke

    About quantum entanglement and relativity of simultaneity

    This looks more like a relativity question, so let's post it here. I try to keep it short. Alice and Bob approach each other, synchronize their clocks when they meet, then drift away from each other with relative speed 0.8c. No acceleration involved here. There is an entangled particle, Alice...
  7. StevieTNZ

    Exploring Quantum Entanglement at a Beam Splitter

    Okay, I have the following scenerio (attached picture). The inputs for path b and c are two photons. both photons aren't entangled with each other - they're entangled to other photons. Before the beam splitter there is a wave plate that converts the photon into the 45/135 basis. So what we...
  8. Physics Monkey

    Entanglement, classical correlation, and questions about superluminal signalling

    The quantum physics forum is full of questions about why entanglement can't be used to signal superluminally. My question is this: do these questions usually still make sense if we replace entanglement by classical correlation? For example, I can send Alice and Bob each a random bit but with...
  9. B

    Entanglement happens at what speed?

    when one entangled particle is measured and its state known the other particle of the entangled pair is described instantaneously collapsing into the same state. What exactly does this mean? does this mean zero time for the pair to take on the same state? I thought the minimum amount of time you...
  10. S

    Quantum Entanglement: The Spooky Connection Between Particles

    Q1: If every atom has to adjust their energy levels according to every other atom in the universe, does that mean that any given single atom has its interior invaded by a catalog of energy states from every other atom in the universe? And only after accounting for all the energy states that...
  11. S

    Why is coherence and entanglement complementary?

    Why is coherence and entanglement complementary? Lets take the case of a pair of entangled photon. there is very little coherence between the entangled photons. when we try to improve the coherence; the (degree of) entanglement starts to reduce. why does that happen? Does it have...
  12. S

    Does Relativity Affect Quantum Entanglement?

    Let's say there's a ship that's traveling at a sufficient velocity from the earth, such that the time is dilated for the ship by an arbitrary factor 10,000. If the ship has an entangled particle connected to another entangled particle on earth, and the entanglement is broken by observation, is...
  13. S

    Can Quantum Entanglement Help Achieve Light Speed?

    I am not a physicist and really do not have any formulas or basis, it is merely a concept that occurred to me and I was curious if it had been thought of or if it was even possible? Conceptual question: Could quantum entanglement be used in conjunction with a photon, to be able to move...
  14. Q

    Is the wave function a relative wave (entanglement)

    Is the wave function a "relative" wave (entanglement) Alice and Bob build a quantum entanglement experiment with the help of a lab technician. The experiment runs and a quantum entangled pair is created but unbeknown to Alice & Bob the technician puts his own measuring device in the...
  15. S

    Is quantum entanglement unaffected by fields/forces?

    Is quantum entanglement unaffected by fields/forces? Forces = the, yet known, four fundamental forces i.e. Is quantum entanglement "friction-less"? Assumption: Anything that is effected by fields and forces can, at the most, interact/move at the speed of light. Quantum entanglement...
  16. P

    Question for understanding photon entanglement

    Photon Entanglement Question Polarize a string of photons vertically. Make the polarized photons into two streams of vertically polarized entangled photon pares. One photon of each pare will go to point A and the other will go to point B. All photons that arrive at point A will encounter a...
  17. R

    How Does Quantum Entanglement Create Spooky Action at a Distance?

    Hi, Lately I've been reading up on quantum entanglement, Bell's inequality, and EPR experiments. My question is fundamental, but I'm asking it here because I haven't yet read an explanation that answers this question (that I recall). Take this typical description of what goes on in an EPR...
  18. E

    Quantum Entanglement and Observation: How Does It Work?

    Now please forgive the question, and thank you in advance for your patience... I am a little confused by the wavefunction collapse upon observation thing (yes, thing is a technical term :-)... So, is it the same as, say I have a 'penny splitter', i.e. 'beam splitter'...I shoot my penny...
  19. LarryS

    How Do Photons Entangle Electrons?

    Say we have a system consisting of two electrons, traveling freely, that are not initially entangled, either in spin or in position-momentum. Then, because of their electric fields, a photon is emitted and absorbed between the two electrons. Are the electrons now guaranteed to be at least...
  20. S

    How stable/fragile is Quantum Entanglement?

    How stable/fragile is Quantum Entanglement? with respect to time, space and various events.Space - We know that experiments have validated QE working across say 150 kms and it is generally believed that they can work across very large distances. Does gravity effect QE over large distances? Time...
  21. M

    Why is quantum entanglement special?

    Clearly, I am a newb at this. However: I was reading a bit on qubits and quantum entanglement and -- though I know that QM has no analog to classical mechanics -- the general concept seems to be: two particles interact and become quantum entangled, and then have non-local ties to each other. To...
  22. S

    How does LHV explain quantum entanglement swapping?

    how does/would LHV (local hidden variables) theory explain the phenomena of: 1. quantum entanglement swapping (where Alice and Bob never meet, and Charlie/Victor is still able to entangle their photons) 2. two-photon interference without the photons ever meeting at the same time-space/place
  23. StevieTNZ

    How to Measure Entangled Photons in the 45/135 Basis with Wave Plates and PBS?

    In regards to measuring two photons in the 45/135 basis using 22.5 wave plates and PBS orientated in the H/V basis: Is it with the entanglement |H>|V> - |V>|H>, with the wave plates: H -> 45 V -> 135 so |45>|135> - |135>|45> And back again using a PBS: |H>|V> - |V>|H> So getting |H>...
  24. S

    Understanding loopholes: what are the loopholes in entanglement swapping?

    what are the loopholes in entanglement swapping (that would say you cannot say for sure quantum entanglement happens/happened)?
  25. LarryS

    Entanglement in QFT: Free Particle Decay

    All definitions of entanglement, that I have encountered, were expressed in the language of non-relativistic QM. Suppose a free, massive particle decays into 2 other massive particles. The 2 new particles would be entangled in linear momentum. Can QFT define that type of entanglement? Any...
  26. K

    Entanglement, Entropy and Energy

    I suppose the meta-question is: Where do I read about this? Engineering major, not physics. Worked through Penrose's book until the tensor calculus on manifolds chapter and then sank without a trace. The popularized descriptions of quantum physics are hopelessly incomplete and as Feynman...
  27. StevieTNZ

    Are Input Photons #2 and #3 Still Entangled After Going Through a Beam Splitter?

    In regards to the attached image; If the input photons were, for input b = photon #2, and for input c = photon #3, where: photon #1 and #2, and #3 and #4 are entangled as |H>|V> + |V>|H>, for the outputs:|H>(b’)|H>(b’) - |V>(b’)|V>(b’) + |H>(c’)|H>(c’) - |V>(c’)|V>(c’) + H(b’)|V>(c’) -...
  28. C

    Quantum entanglement and Bose-Einstein condensation.

    Good afternoon. I am wondering if quantum entanglement could be created between two thermodynamically isolated Bose-Einstein condensates of the same atom produced at the same time in close proximity. Due to the similarity of the systems' mathematics regarding their quantum states (wave...
  29. S

    Proving Entanglement - Do we need Bells Theorem?

    Question: Do we really need to spend too much time on Bell's theorem/test when there are numerous/easier proofs of quantum entanglement? The numerous/easier proofs are: - Almost all experiments in which two photons are generated via a) SPDC (Delayed Choice Quantum Eraser, Mach–Zehnder...
  30. StevieTNZ

    What is entanglement purification and how does it work?

    I was hoping if someone could briefly explain entanglement purification. I’ve read http://www.lsr.ph.ic.ac.uk/~plenio/cp394311998.pdf , but because I’m not mathematically inclined most of it isn’t sinking in. What I gather is in the beginning you share two entangled states, and one of the...
  31. I

    Quantum entanglement communication

    Hi, I've been reading some stuff about quantum entanglement and I stumbled upon an article talking about a delayed choice quantum eraser experiment using parametric down conversion. I was wondering if it was possible to communicate a signal through to the other side faster than light...
  32. A

    Why is quantum entanglement difficult to realize?

    When I read about entanglement it is described as the singlet state two particles (or eventually even molecules) are in after interaction with each others or due to a decay. Put in that way it does not sound difficult to do. Just let two particles scatter with each others and we should have an...
  33. C

    Is Quantum Entanglement a Means of Evil Communication Across the Galaxy?

    Physicist say "Quantum Entanglement is when you place 2 electrons together. They Vibrate in Unison. When you take them across the galaxy if you "jiggle" one, The other also "jiggles" Physicist say" however it does not transfer any meaningful information"This is a EVIL way of speaking. Why...
  34. N

    Does entanglement describe continuity at the micro level?

    I'm a new poster; I hope don't violate rules or policy. Am I wrong, or is the rule essentially that a particle isn't finished interacting with the last particle on it's world path unless and until it interacts with a third? This isn't what I might have guessed about physical continuity, but it...
  35. S

    Pauli's exclusion principle and quantum entanglement

    The Pauli exclusion principle: is the quantum mechanical principle that no two identical fermions (particles with half-integer spin) may occupy the same quantum state simultaneously Quantum entanglement: the type of interaction is such that each resulting member of a pair is properly...
  36. R

    Would traveling faster than the speed of light solve the entanglement issue?

    I do not know a lot about physics, however, I was wondering if anyone would know, now that they think something can travel faster than the speed of light, would that solve the entanglement issue in quantum mechanics or at least the problem Einstein had with it? Or how two particles would be...
  37. sergiokapone

    Quantum entanglement of spin along multiple orthogonal axes

    I already asked this question on physics.stackexchange.com, but did not get the desired response. I am interested in the opinion of your community. Picture an entangled pair of spin 1/2-spin particles with total spin 0. In the diagram, particle 1 of the pair is moving to the left (-y), and...
  38. D

    HOW can entanglement be observed experimentally?

    hi all i have two questions. 1. Quantum entanglement is observed experimentally. But how can that be. Does not Quantum decoherence effect it from being observed? 2.The general notion is that M String theory if proven is theory of everything. But without explaining entanglement how does it...
  39. S

    Question on quantum entanglement mechanism

    Hello, I can understand only the basic principle behind quantum entanglement. Do you guys know of the mechanism by which it works? I understand that there is no information being transferred between particles that react under entanglement. So what then is the hypotheses as to how one particle...
  40. S

    Quantum entanglement and measurement operator

    Homework Statement A system in a state \frac{1}{\sqrt{2}}(\left<\phi\right| + \left<\psi\right|) undergoes an interaction with a second system (which is initially in \left<\alpha\right|) and ands up in an entangled state \frac{1}{\sqrt{2}}\left(\left\langle\phi\right| \otimes...
  41. StevieTNZ

    Entanglement Swapping: A and X Polarization Explained

    Hi there, If we set-up an experiment for entanglement swapping, the two entangled pairs of photons are: Group 1: A, B Group 2: X, Y Take B and Y and perform a Bell-state measurement on them. Obviously A and X are now entangled. But for this to occur, must B and Y have no definite...
  42. J

    Can Entangled Photons Be Used for Instantaneous Morse Code Communication?

    the entangled photon was sent 10 miles i believe, doesn't matter. my question is, once the polarization change is viewed on the receiving end, can the observation of the entangled photons ppolarization change be viewed more than once per entanglement? or could the two ends essentially send...
  43. F

    Unraveling the Mysteries of Quantum Entanglement: Implications and Applications

    That quote is from this article.. http://www.physorg.com/news/2011-05-vienna-physicists-quantum-twin-atoms.html I thought that's exactly what entanglement meant. Can someone please explain entanglement better then? I am miss understanding Schrodinger's cat experiential.
  44. StevieTNZ

    Understanding GHZ Entanglement

    Hi there, I was looking through Zeilinger's "Dance of the Photons" where I re-read the section of three-photon entanglement. If one photon is measured in H polarisation, the other two take on H - likewise with V polarisation. What I find interesting is if we measure one photon and its H...
  45. T

    Orchestration of Quantum Entanglement

    How and where is quantum entanglement orchestrated? Does it require a deeper, non-spacial level of existence where the distance between entangled particles is irrelevant?
  46. N

    How photon entanglement works?

    How do you get photos to become entangled? And is this even possible, or just a theory?
  47. K

    Is entanglement still considered spooky ?

    Is entanglement still considered "spooky"? Even now in 2012, you often hear the phrase "spooky action at a distance" regarding entanglement. Is this just a popular-science cliché, or do some physicists really consider EPR effects (e.g. Alice sees spin-up, therefore Bob must see spin-down)...
  48. T

    Quantum Entanglement in a Human Brain

    Hi Do the experts on this forum think that it is possible for there to be special particles scattered throughout the volume of a living human brain which together form a single permanent quantum entanglement which lasts at least as long as the lifetime of the brain? If yes, what do you think...
  49. S

    Question about quantum entanglement

    Hello everyone, I have a basic understanding of quantum entanglement. One thing I don't understand is the following: For particles to be entangled, is it necessary to produce the entanglement via whichever means, or are all particles entangled to another particle to begin with? By the latter, I...
  50. StevieTNZ

    Exploring the Role of Wave Plates in Entanglement: A Question of Measurement?

    If we produce a three-pair of entangled photons, and send two of them towards polarising beam splitters, and one towards a vertically aligned wave plate - according to QM we need to describe the photon as being in a superposition of V and H when they hit the beam splitters, but when the photon...
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