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Quantum Theory Experiment Said to Prove ‘Spooky’ Interactions
- biswaroop 11y agoI wish they used a better title. Entanglement is not a kind of interaction, and I wonder what a "quantum theory experiment" is.
- greeneggs 11y agoIt isn't just the title, the whole article is poorly written. It gives the impression that faster-than-light communication is possible. From the first sentence: "[Scientists] conducted an experiment they say proves one of the most fundamental claims of quantum theory — that objects separated by great distance can instantaneously affect each other’s behavior." Emphasis mine. This is totally wrong. The second sentence: "The finding is another blow to one of the bedrock principles of standard physics known as “locality,” which states that an object is directly influenced only by its immediate surroundings." Again, this is wrong. Quantum physics is entirely consistent with locality. It contradicts "local hidden variable models." Despite the similar name, this is different from locality. (Local hidden variable models are local, classical models.)
- tbabb 11y agoTo add to that, Bell's theorem says that either locality or hidden variables may be true, but not both. We could construct a formulation of quantum mechanics that includes hidden variables, but must account for the state of the universe at arbitrarily distant locations.
- finnh 11y agoI posted this b/c I was hoping someone would dive into these quotes: The Delft researchers were able to entangle two electrons separated by a distance of 1.3 kilometers, slightly less than a mile, and then share information between them. ... Researchers like Dr. Hanson envision a quantum communications network formed from a chain of entangled particles girdling the entire globe. Such a network would make it possible to securely share encryption keys, and know of eavesdropping attempts with absolute certainty. This implies that entanglement allows faster-than-light communication (transmitting arbitrary information across the entangled link). I thought that was a no-no, and that entanglement still didn't allow FTL communication despite FTL-like properties. Can somebody help out here?
- zardo 11y agoIt doesn't allow (non-random) FTL communication. You can use it to generate the same random number in two locations.
- fizx 11y agoWhile everything you said is true, I feel its worth pointing out entanglement is stronger than simply being able to generate the same number in two locations, a feat easily accomplished via classical means. Edit: Entanglement is akin to the following... Assume Alice and Bob are distantly separated. Alice has an arbitrary float variable called x. Alice and Bob both have a function rand() generating floats between zero and one, with a shared seed so that they can both generate the same random numbers. Classical correlation is that they both can call rand() with their identical seeds to get the same random numbers. Entanglement is that Bob's rand() is actually ((x + rand()) % 1), where Bob instantly and magically has access to Alice's variable x. No information can be transmitted, because the distribution of random numbers hasn't changed, and Bob doesn't have direct access to x. But something is different, and if Bob is clever, he might be able to do some fun stuff. This isn't a perfect analogy, but perhaps it helps.
- duaneb 11y ago> While everything you said is true, I feel its worth pointing out entanglement is stronger than simply being able to generate the same number in two locations, a feat easily accomplished via classical means. Really? That's not random, that's pseudo-random, so the secret is still just the seed distributed before hand. True randomness would be entirely uninvolved from other state, including location or time. This is really just combining the sharing and the generating into one process so you CAN share true randomness without sharing other state.
- tgflynn 11y agoI'm not an expert but quantum entanglement definitely does not allow FTL communication. I believe quantum key sharing requires a classical channel in addition to the quantum channel, hence no information is transmitted faster than light.
- MPSimmons 11y agoCan someone convince me that there aren't hidden variables? Because my puny monkey brain hears "a variable can be one of two states, but in the beginning, it's in a super-position of them. When measured, the state is determined." and it's a relative easy thing to get. But.... "There are two particles entangled together such that when one becomes up or down, the other becomes the opposite, and measuring either will determine both, instantaneously, regardless of distance" is a much harder thing to swallow. Occam's Razor says that there are hidden variables that are pre-selecting state, and we just don't know about them until we measure. ESPECIALLY when one of the requirements for the system is that we can only measure, not influence the outcome of the measurement. So please, someone who knows more than I do - why can't there be hidden variables being set at entanglement that pre-determine the measurement outcome?
- weinzierl 11y agoBell's theorem is the keyword you should look up[1]. If you are more a CS type than a physicist understanding the CHSH game might help. "Lecture 20: Bell inequalities and nonlocality" from John Watrous of the University of Calgary [2] is a short and accessible introduction to the CHSH game. fizx mentioned Scott Aaronson's "Bell inequality violation finally done right" [3] which is about the same recent experiment as the NYT article but much better. It contains a concise description of the CHSH game. [1] https://en.wikipedia.org/wiki/Bell's_theorem https://en.wikipedia.org/wiki/Bell's_theorem [2] https://cs.uwaterloo.ca/~watrous/CPSC519/LectureNotes/20.pdf https://cs.uwaterloo.ca/~watrous/CPSC519/LectureNotes/20.pdf [3] http://www.scottaaronson.com/blog/?cat=33 http://www.scottaaronson.com/blog/?cat=33
- jahnu 11y agoAs with many of these types of things I recommend checking if there is a simple English version too. https://simple.wikipedia.org/wiki/Bell's_theorem https://simple.wikipedia.org/wiki/Bell's_theorem
- deleted 11y ago[deleted]
- dang 11y agoAlso the experimenters' page on this: https://news.ycombinator.com/item?id=10428397 https://news.ycombinator.com/item?id=10428397.
- imglorp 11y ago> particles do not take on formal properties until they are measured or observed in some way This sounds like lazy evaluation.