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Physicists Create Quantum Link Between Photons That Don't Exist at the Same Time
- dxhdr 13y agoAt the risk of being "that guy," a few thoughts popped into my head after reading this article. I couldn't help but reflect on the possibility of us just completely misunderstanding how the universe works. It wouldn't be the first time in history. What if: Our concept of time and matter is wrong, or our idea of quantum physics is interesting and useful, but ultimately wrong. Perhaps I'm just a simpleton but part of me really wants to believe we're missing something fundamental that would make all of this so much easier to accept and understand.
- breadbox 13y agoYou're only the ten millionth person to voice that desire. Sadly, the universe is not obligated to be intuitive. At this point we probably have to accept that the parts of the universe that we didn't evolve to understand are free to be as utterly weird as they want to be.
- dxhdr 13y agoSure, but what are the odds the universe fundamentally defies intuitive logic versus the odds our small brains currently can't see the full picture but in the meantime have invented insane (but cool) mathematical machinations? I guess it's unknowable.
- breadbox 13y agoBut what do you think physicists do all day? Exactly what you just described. Unfortunately we pretty much have the answer, and it's kind of a resounding NO. Look up "local hidden variable theory".
- ThomPete 13y agoLets not put pollute this discussion with that piece of wishful thinking :)
- mathewsanders 13y agoplease read Anathem http://www.amazon.com/Anathem-Neal-Stephenson/dp/0061694940/ref=sr_1_1?ie=UTF8&qid=1369336883&sr=8-1&keywords=Anathem http://www.amazon.com/Anathem-Neal-Stephenson/dp/0061694940/... (if you've not already) I think you will enjoy it :) [edit: removed wikipedia link... too many spoilers :(]
- johntb86 13y agoIn that case it turns out that some extremely simple intuitive rules can generate some very unintuitive results. Those results may perhaps best be approximated by extremely complicated mathematics. c.f. chaos theory and turing equivalent 1-d cellular automata.
- caf 13y agoI can't see any basis on which to assign the probabilities you ask for. A better question might be: on what basis do you believe that the universe should be intuitive? Why should it be so?
- cristianpascu 13y agoWe're most certainly missing a lot of things. But quantum mechanics is in no way wrong. It may not be complete, but not wrong. Ontologically, there is not reason for us not to discover other things about nature that are (more) fundamental.
- obstacle1 13y agoYou sound far too certain for my liking. But IANAP.
- z5h 13y agoI think the fundamental problem is the idea that there is more than one thing. As soon as you see there is only one thing, it's no surprise that everything is related. http://philosophy.stackexchange.com/q/4751/2992 http://philosophy.stackexchange.com/q/4751/2992
- charlieflowers 13y agoBut in that case, wouldn't physics be non-local after all? Do you believe that it is non-local?
- gschorno 13y agoDon't worry, in 500 years, after everything that is now studied is well understood, there will be one or more underlying principles discovered which will simplify it all.
- axus 13y agoIt is sobering to realize there are some things I'll never understand. But it's OK. Ignorance let's us have more fun speculating. I was wondering, are two entangled particles actually the same particle, where one or both "took a time machine" to get to the other place?
- charlieflowers 13y agoThis train of thought has to have something to it. There is obviously something that is "the same". Perhaps it is something more fundamental than the photons that "generates" the photons. Or, if it doesn't "generate" them, it determines the state of them at least. In "Many Worlds", the "something" would be the particular universe that "this instance" of ourselves ended up in.
- ThomPete 13y agoAnyone who claims they understand Quantum Physics, doesn't understand Quantum Physics – Feynman
- genwin 13y agoIf you are not completely confused by quantum mechanics, you do not understand it - Bohr
- Xcelerate 13y agoAt a mathematical level, it's pretty elegant how quantum mechanics works. At the level of the article, not so much. Once you get the math (and it really kind of clicks all at once), it's not too hard. The problem is that the math has a lot of historical baggage and the ways of translating equations into prose are not the most effective I think. The whole "uncertainty" thing bothers me. I think there's better ways of expressing this concept to the public. I am, however, bothered by the fact that QM is not deterministic. Most experiments have ruled out loopholes for a deterministic universe, but it still just weirds me out that randomness is inherent to the measurement of observables.
- indenturedsmile 13y agoDo you have any sources for experiments ruling out our universe being deterministic? I'm not questioning you. I honestly have always been intrigued with the idea. Thanks.
- lmm 13y agoThe standard answer is the Bell inequalities, but if you only care about deterministic vs. nondeterministic then Conway's "free will theorem" is a bit simpler. (The result is that either which quantities we choose to measure must be deterministic, or physics must be nonlocal (i.e. what we do in one place can change what we measure in another place even if the two experiments happen simultaneously), or the results of our measurements must be nondeterministic)
- Retric 13y agoNothing says we live in a local universe.
- lmm 13y agoThere's no proof, sure. But nonlocality is very counterintuitive, arguably more so than nondeterminism (and there are no familiar classical/macroscopic phenomena that exhibit nonlocality, whereas many familiar things at least appear nondeterministic in practice).
- lmm 13y agoIt's possible (in fact almost certain) that we don't know anything, but it's unlikely that we're missing something that would make it easier to accept: any true theory of physics would have to explain nonintuitive experimental outcomes like the bell inequalities or the "free will theorem". FWIW, if one bites the bullet and assumes the equations mean what they appear to mean then it's a lot simpler than you might think. My first thought on looking at the diagram in the article was "well duh".
- mindcrime 13y agoYou may not be so "out there" at all. There were two books that came out a few years ago, both basically lambasting the state of physics - especially string theory. One was titled Not Even Wrong[1] and the other was titled The Trouble With Physics[2]. As best as I can tell, of the two (and I'm afraid I can't remember which it was now) made the case that we might be completely wrong about the nature of time. The idea was that the reason we have had to resort to such (seemingly) byzantine theories as string theory, without seeming to make much progress on deciding which string theory is correct (or if it's correct at all) is tied up in this misunderstanding of time. IOW, before we make any really fundamental breakthroughs in physics, we will have to re-conceptualize time itself. Now that's a pretty bold claim, and I have no idea if it is correct or not. But it's a position held by at least one fairly well known and reputable physicist. [1]: http://www.amazon.com/gp/product/0465092756 http://www.amazon.com/gp/product/0465092756 [2]: http://www.amazon.com/The-Trouble-With-Physics-Science/dp/061891868X http://www.amazon.com/The-Trouble-With-Physics-Science/dp/06...
- iandanforth 13y agoDoes this work only in one direction? Is there any reason to see the first measurement as causal? Could the second measurement be interpreted as causal that then propagates backward in time? I'm really trying to get at if the linear description of events in the article is just a convenient simplification, or if physicists thinks that there is time order here.
- breadbox 13y agoThe first measurement is in no way causal. It's just that the whole point of the experiment was to show that entanglement occurs even when the photons don't coexist. If you didn't make the first measurement, then there wouldn't be anything different from the original experiment.
- drostie 13y agoI don't know precisely what you're asking because the whole point is that there are three measurements (measure qubit 1, entangling-measure qubits 2 and 3, and measure qubit 3) whose time-order does not matter. There is a nice theorem in quantum computing that you can defer all measurements to the end of a set of operations if you replace all of the classical logic with appropriate quantum gates; conversely, you can measure as soon as you want if those quantum gates can be replaced with classical logic. Here, conveniently, there are no gates; so the theorem says that you get entangled results even though the entangled things don't exist simultaneously, because they could have if you'd pushed the measurement to the end of the experiment. The linear description of events describes the time-order that the actual experiment used.
- Steuard 13y agoMy best understanding is that in general, issues related purely to quantum entanglement are entirely unrelated to causality. As noted in the article, even the "spooky action at a distance" that made Einstein so uncomfortable cannot be used to transmit information faster than light. I haven't checked the math, but I assume that the same sort of properties mean that this system couldn't be used to transmit information into the past. So issues of causality don't really arise: this is just a neat demonstration that the weird correlations implied by quantum mechanics can be separated in a "direction" that hadn't been tested before. (That is, there's definitely time passing in this system and there is definitely entanglement between objects existing at different times, but there's also no real tension between those facts.)
- deleted 13y ago[deleted]
- ivan_ah 13y agooriginal article is here: http://arxiv.org/abs/1209.4191 http://arxiv.org/abs/1209.4191
- Schiphol 13y agoIf one abandons the idea that there is a privileged 'now' (what philosophers call the A-theory of time, which is already difficult to make compatible with special relativity) this effect is not weirder than simultaneous entanglement -- admittedly, this is already sufficiently weird. (Most physicists, and most philosophers, believe that the right theory of time is a B-theory of time: once every event is lain down in a four-dimensional spacetime diagram, there is nothing else to describe; no facts, in particular, about which of these different times is really now, the time at which the whole universe is.)
- ywang0414 13y agoLet's use this to keep a client in sync with the server. And also keep multiple instances of server in synch with each other.
- krcz 13y agoCould they possibly create 1-2 and 3-4 entangled pairs at the same time, measure 1 & 4 and then use this "projective measurement" trick to entangle 3 and 4? If so, could this affect the measurements of 1 and 4 in the past?
- pep-ok 13y agoyes, i think, if you mean 2 and 3. you have 1-2 and 3-4, then you entangle 1-4 which I think should lead to 2-3 entanglement without the 2-3 couple ever interacting at all. I think it is called entanglement teleportation.
- krcz 13y agoYeah, I've meant entangling 2 & 3 pair and measuring 1 & 4. But my concern is if we can still use this trick after measuring 1 & 4?
- pep-ok 13y agoI am not sure I understand you.
- krcz 13y agoI hope that can make things clear: http://imgur.com/5mfB4m0 http://imgur.com/5mfB4m0 .
- Dylan16807 13y ago>For example, last year a team showed that entanglement swapping still works even if they make the projective measurement after they’ve already measured the polarizations of photons 1 and 4. So yes, they can. Which leaves me wondering which option is right: A. I'm missing something major here. B. They can measure 1 and 4 and then decide whether to use their box on 2 and 3 and contradict causality. C. This experiment isn't actually exciting at all and the 'entanglement' isn't the good kind.
- scotty79 13y ago
- jmanamj 13y agoThe question now is, how to use this to mine Bitcoins?
- TheEzEzz 13y agoI'm a little baffled when articles come out claiming some weird relativity-breaking quantum effect and fail to mention that the no-collapse interpretation of quantum mechanics explains the effect easily without breaking relativity.
- hiker 13y agoWhat's the easy no-collapse interpretation explanation?
- jaibot 13y agoI'm guessing Ez is referring to the Many Worlds Interpretation.
- oofabz 13y agoThere are a few, the most realistic is the Bohm interpretation: http://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory http://en.wikipedia.org/wiki/De_Broglie%E2%80%93Bohm_theory The basic idea is that observed decoherence is not caused by wave collapse, but is caused by interaction with noise. For example, consider the double-slit experiment. If you allow light to pass through two slits, it forms an interference pattern. If you put a detector in one of the slits, the pattern collapses. The Copenhagen interpretation says this is because the observation collapses the waveform of the photon. The Bohm interpretation says that the photon interacted with your detector and its phase was knocked out of sync.
- calhoun137 13y agoI love how at the end of all these physics articles there is always some guy who is like "O HELL YEA WE CAN USE THIS FOR QUANTUM COMPUTERS!"
- femto 13y agoThose are probably the magic words that make the state security apparatus throw wads of cash at you.