susskind described entanglement in a bit different way than I'd heard - "that entanglement allows one to know everything there is to know about a system of particles (the whole), while knowing nothing about it's parts."<p>In the classical version of an information experiment, if i randomize placement of objects A and B into 2 boxes, and send one of those boxes to someone else - upon opening my box I instantly know whether the other box contains object A or B. The Quantum Mechanical version of the above experiment is very similar, except there could be several different degreees of freedom to measure on upon opening my box (what angle of spin measure on, etc..)<p>So to me, that doesn't suggest that something "traveled" to the other box, just like in the Classical version.<p>Rather, somehow I only "knew" the system at the beginning without knowing "any of it's parts" (due to entanglement & superposition).<p>Then, just observing a degree of freedom in one the parts finally reveals what the corresponding degree of freedom in the other part was.<p>This (intuitively) makes more sense to me than saying "information traveled" and "action at a distance"
Why does this not describe the "entanglement" phenomenon:<p>1) Alice, Bob, and Charlie are in a room.<p>2) Alice has only an apple and a pear, seen by Charlie.<p>3) Charlie leaves the room.<p>4) Alice gives one of the two fruits to Bob.<p>5) Bob leaves the room to meet up with Charlie and starts eating the pear.<p>6) Charlie instantly knows that Alice has the apple, no matter where she has ended up in the universe (which is not spooky at all).
Oh cool! This experiment is very fun, not just from the results side. I was able to get a tour with the photonic side of this set-up (not the atomic side, as this paper elucidates). The photons are made entangled, then split and sent into some fiber-optic cables that run about in the tracts in the hallways. The rooms used to measure the entanglements are sufficiently far apart, but due to budgets, are at right angles from the source. We only went to one of the rooms, but the measurement devices are housed in marijuana grow pods you can buy, as they tend to keep the temperature stable, have access for the wires and cryogenic tubes, will keep out/in EM noise, and are pretty cheap. There was a line on the floor of that room, off in the corner, that had where the 'light speed' signal from the other measurement room stopped when the measurement (in the room we were in) was made, proving that the measurements could not interact. If you ever get a chance, get a tour at NIST, it is well worth whatever strings you have to pull. Getting to see <i>The</i> United States Second (where the US measures all of out time from) was a real highlight of my scientific career.
One think I've been wondering about spooky action is if entanglement reactions are bound to the speed of light. As in, if one particle of the entangled pair is manipulated, is there a "signal" that is "transmitted" at some speed? Or is it "instant" in the sense that it transcends lightspeed? Or does this question even make sense in this context? Quantum stuff gets weird fast since we have very little basis in which to intuit it.
One of the more head exploding experiments I've seen regarding entanglement is this one:<p><a href="https://youtu.be/u9bXolOFAB8" rel="nofollow">https://youtu.be/u9bXolOFAB8</a><p>By all apparences, it seems to violate causality. It's one of those things that make you suddenly stop and bemusedly wonder if maybe we've finally found a kludge in the Universe's code.<p><i>edit</i> BTW, if you'd like to know more about this experiment and why it has ridiculous implications, check this PBS clip: <a href="https://youtu.be/8ORLN_KwAgs" rel="nofollow">https://youtu.be/8ORLN_KwAgs</a>