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Phymath
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What is quantum entanglement? why is it "spooky"
Its been a very long time since I've thought about these things so I'll try to recall what I can - Consider a system of two particles. Measurements on the system effects the entire system, not just part of the system, i.e. not just one particle. Thus, for example, if you have a system of two particles which is in a quantum state for which the spins must always be in opposite states when you measure them then the spin of one particle must be measured to be the opposite of the spin of the other particle and hence the spin of the other particle is determined by the measurement of the spin of the first particle. Since the particles were not in a particluar state before the measurement then eacb particle acquired the particular spin upon measurement. Thus if two particles are separated by a finite distance and you measure the spin of one then instantaneously the spin of the otherone is determined, i.e. the spin of the other particle falls into a particular, measureable, state. This requires the cause to travel instantaneously and thus faster than the speed of light, contrary to what one would predict from relativity. This means that one can choose a frame of reference in which one measurement occurred before the other and you can also choose a frame of reference in which the opposite is true - thus causality gets all messed up.Phymath said:What is quantum entanglement? why is it "spooky"
Yes.Phymath said:so ur saying that the other particle takes the opposite spin, when measured, but because the uncertianty principle the spin has not already been determined until u measure it?
You missed the point. I was talking about two particles. Not one. If you were to flip the light switch on in your room to turn the light bulb on and at the exact same time a light came on at the exact same time in a room 20 light years away as a directy result of you tossing that switch then would you think that was odd?.. see i don't understand why this is odd, if i were to spin a ball in space (no external forces) and leave when i come back why would it be odd for me to look a the ball as still spinning? like why is measuring it odd?
pmb_phy said:This requires the cause to travel instantaneously and thus faster than the speed of light, contrary to what one would predict from relativity. This means that one can choose a frame of reference in which one measurement occurred before the other and you can also choose a frame of reference in which the opposite is true - thus causality gets all messed up.
Pete
marlon said:Hi,
This is a misconception.
Suppose you have two ensembles each provided with an entangeled state that you describe. Both ensembles are described by precisely the same density matrix. Thus, there is no conceivable measurement that one obersver can do that will distinguish the two ensembles. Also, there is no way the observer 1 can determin what measurement observer 2 performed. The message is unreadable. For example the outcome will be 50% chance of spin UP and 50% change on spin down...
regards
marlon
Phymath said:What is quantum entanglement? why is it "spooky"
caribou said:What isn't controversial is "nonseperability" and that we can't talk about the properties of one particle which is entangled without mentioning the properties of any other particles it is entangled with.
"Entanglement" is just another way of saying "correlated".
Phymath said:Or are you trying to show me that when its made its both spinning up and down but measuring it directly forces the other one to be the opposite in an instant.
Quantum entanglement is a phenomenon in quantum mechanics where two or more particles become connected in such a way that the state of one particle is dependent on the state of the other, regardless of the distance between them.
Quantum entanglement occurs when two particles are created or interact in such a way that their properties become linked. This link between the particles remains even if they are separated by large distances, meaning that any change in one particle will cause a corresponding change in the other.
Quantum entanglement is a fundamental property of quantum mechanics and is caused by the superposition principle, which states that particles can exist in multiple states at once. When two particles become entangled, their states become linked and cannot be described independently.
Quantum entanglement is significant because it allows for instantaneous communication between particles, regardless of the distance between them. This has important implications for quantum computing, encryption, and teleportation.
Quantum entanglement is being used in technologies such as quantum cryptography, quantum computing, and quantum teleportation. These technologies take advantage of the instantaneous communication between entangled particles to create secure communication channels and powerful computing systems.