L&FP, 65f: It’s all tangled up — quantum entanglement (vs how we tend to talk loosely)

6 Replies to “L&FP, 65f: It’s all tangled up — quantum entanglement (vs how we tend to talk loosely)”

1. 1
   kairosfocus says:

   February 14, 2023 at 2:44 am

   L&FP, 65f: It’s all tangled up — quantum entanglement (vs how we tend to talk loosely)
2. 2
   kairosfocus says:

   February 14, 2023 at 2:47 am

   F/N: Wikipedia is interesting:

   Quantum entanglement is the phenomenon that occurs when a group of particles are generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the group cannot be described independently of the state of the others, including when the particles are separated by a large distance. The topic of quantum entanglement is at the heart of the disparity between classical and quantum physics: entanglement is a primary feature of quantum mechanics not present in classical mechanics.[1]

   Measurements of physical properties such as position, momentum, spin, and polarization performed on entangled particles can, in some cases, be found to be perfectly correlated. For example, if a pair of entangled particles is generated such that their total spin is known to be zero, and one particle is found to have clockwise spin on a first axis, then the spin of the other particle, measured on the same axis, is found to be anticlockwise. However, this behavior gives rise to seemingly paradoxical effects: any measurement of a particle’s properties results in an irreversible wave function collapse of that particle and changes the original quantum state. With entangled particles, such measurements affect the entangled system as a whole.

   Such phenomena were the subject of a 1935 paper by Albert Einstein, Boris Podolsky, and Nathan Rosen,[2] and several papers by Erwin Schrödinger shortly thereafter,[3][4] describing what came to be known as the EPR paradox. Einstein and others considered such behavior impossible, as it violated the local realism view of causality (Einstein referring to it as “spooky action at a distance”)[5] and argued that the accepted formulation of quantum mechanics must therefore be incomplete.

   Later, however, the counterintuitive predictions of quantum mechanics were verified[6][7][8] in tests where polarization or spin of entangled particles was measured at separate locations, statistically violating Bell’s inequality. In earlier tests, it could not be ruled out that the result at one point could have been subtly transmitted to the remote point, affecting the outcome at the second location.[8] However, so-called “loophole-free” Bell tests have been performed where the locations were sufficiently separated that communications at the speed of light would have taken longer—in one case, 10,000 times longer—than the interval between the measurements.[7][6]

   According to some interpretations of quantum mechanics, the effect of one measurement occurs instantly. Other interpretations which do not recognize wavefunction collapse dispute that there is any “effect” at all. However, all interpretations agree that entanglement produces correlation between the measurements, and that the mutual information between the entangled particles can be exploited, but that any transmission of information at faster-than-light speeds is impossible.[9][10]

   Quantum entanglement has been demonstrated experimentally with photons,[11][12] electrons,[13][14] and even small diamonds.[15]

   KF
3. 3
   relatd says:

   February 14, 2023 at 11:10 am

   No big deal. Watch the following to learn how entanglement has been dealt with in quantum computers.

   https://www.youtube.com/watch?v=-UlxHPIEVqA
4. 4
   kairosfocus says:

   February 14, 2023 at 2:31 pm

   Relatd, that’s for later. The concept itself needs clarification. KF
5. 5
   JVL says:

   February 16, 2023 at 2:16 pm

   Just read a very good (I think) article explaining the three (3!) major ways of interpreting (or not) quantum mechanics.

   https://arstechnica.com/science/2023/02/a-guide-to-not-understanding-quantum-mechanics/

   I tend to be a real Copenhagen person myself but that third interpretation . . . sounds interesting.
6. 6
   kairosfocus says:

   February 17, 2023 at 5:38 am

   JVL, an interesting article, especially I liked:

   take the familiar concept of a quantum jump. An electron in an atom changes energy levels and thus either absorbs or emits energy in the form of one photon of radiation. No big deal, right? But how does the electron “jump” from one energy level to another? If it moves smoothly, like literally everything else in the Universe, we would see the energy involved change smoothly as well. But we don’t.

   So does the electron magically disappear from one energy level and magically reappear in another? If it does, name one other physical object in the Universe that acts like that. While you’re at it, please give me a physical description of the unfolding of this magic act. I’ll wait.

   Quantum mechanics is completely silent on how the electron changes orbitals; it just blandly states that it does and tells us what outcomes to expect when that happens.

   The “[a]ccording to some estimates, roughly a quarter of our world’s GDP relies on quantum mechanics” gives pause, though in the end it implies that electronics and related technologies are baked into just about everything.

   I think Copenhagen and shut up and calculate are usually seen as different, but there is a point.

   Pilot waves, though, are a hidden variable theory and are dead. Save, maybe you can imagine that a probability wave is some sort of guidance.

   We always come back to that low intensity particle beam with each particle interfering with itself in a double slit experiment.

   KF