tag:blogger.com,1999:blog-22973357.post8404569957869614201..comments2023-09-27T07:44:19.769-04:00Comments on Sabine Hossenfelder: Backreaction: 10 Essentials of Quantum MechanicsSabine Hossenfelderhttp://www.blogger.com/profile/06151209308084588985noreply@blogger.comBlogger49125tag:blogger.com,1999:blog-22973357.post-63921801628113003832016-05-01T21:51:07.061-04:002016-05-01T21:51:07.061-04:00Frank Wilczek just wrote an article @ Quanta, &quo...Frank Wilczek just wrote an article @ Quanta, "Entanglement Made Simple"<br />https://www.quantamagazine.org/20160428-entanglement-made-simple/ <br />although 'simple" depends on your point of view, I suppose!<br /><br />As a non-professional physicist, I was astonished by Wilczek's description of the GHZ effect.<br /><br />The world is stranger than we (most of us, anyway!Unknownhttps://www.blogger.com/profile/14136922143569965933noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-88964187996460071512016-04-12T08:25:21.506-04:002016-04-12T08:25:21.506-04:00Hi Sabine, your answer depends upon how one define...Hi Sabine, your answer depends upon how one defines measurable questions. For example, in QFT axiomatics one would postulate that the only admissible questions are those who commute at spacelike distances; one proceeds then to verify that for Bosonic particles the field operator satisfies this demand while for Fermionic particles one has to take some square of the field operators due to the johnhttps://www.blogger.com/profile/06523031889979043404noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-47220007286729574652016-04-11T15:10:30.889-04:002016-04-11T15:10:30.889-04:00"The problem is that decoherence still leaves..."The problem is that decoherence still leaves you with the probabilistic (mixed) state, rather than one particular measurement outcome."<br /><br />Why is that a problem? The observer's brain is part of the overall quantum system, and its state gets entangled with the state of what is being measured, so you only get brain states that perceive one particular measurement outcome.<br /Kevin S. Van Hornhttps://www.blogger.com/profile/07591228017757297031noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-61672348969081442272016-04-11T11:11:49.909-04:002016-04-11T11:11:49.909-04:00Given chiral composite object diffraction, what in...Given chiral composite object diffraction, what interacts at the grating? Diffracted (Schrödinger's cat configuration) single enantiomer camphor may racemize. Diffraction racemization of a multiply-connected stabilomer (thermodynamic deep hole in the energy hypersurface) chiral cage with many rotational symmetries is a stronger test. <b>Look</b>, then theorize.<br /><br />http://Uncle Alhttps://www.blogger.com/profile/05056804084187606211noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2382847661190075502016-04-11T01:12:13.762-04:002016-04-11T01:12:13.762-04:00Noa,
Yes, I can - but it's quite off-topic he...Noa,<br /><br />Yes, I can - but it's quite off-topic here. It's an interesting question though, I'll answer this in an upcoming "Dear Dr B" column. Best,<br /><br />B.Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-22249394691436034552016-04-11T01:10:32.977-04:002016-04-11T01:10:32.977-04:00livefire,
There are actually proposals now to do ...livefire,<br /><br /><a href="http://backreaction.blogspot.com/2016/03/researchers-propose-experiment-to.html" rel="nofollow">There are actually proposals now to do it for milligram objects.</a> You have to be careful though with what it is that you "see". You see the effect of quantum superpositions, you never actually measure a state in a quantum superposition. (And the article doesn&Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-62057456761516229612016-04-09T08:29:14.336-04:002016-04-09T08:29:14.336-04:00The notion that interactions with the environment ...The notion that interactions with the environment prevent the observation of superpositions seems simple enough at first glance. Except I'm fuzzy on where this "environment" comes from. The universe began as some sort of object so small it was surely a quantum state of some sort. It's hard to see why it wouldn't be a superposition. Without an environment to interact with, S Johnsonhttps://www.blogger.com/profile/11610068751705809284noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-37592031649240145252016-04-09T07:10:54.999-04:002016-04-09T07:10:54.999-04:00Hello Sabine,
Could you elaborate (even) more on ...Hello Sabine,<br /><br />Could you elaborate (even) more on your last paragraph concerning the exact tension between Lorentz invariance and attempts for discretisation ?<br /><br />Best,<br /><br />NoaKoenraad Van Spaendonckhttps://www.blogger.com/profile/15090279727324831109noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-25660259835691207242016-04-09T01:58:17.367-04:002016-04-09T01:58:17.367-04:00JimV,
Whether or not nature is fundamentally '...JimV,<br /><br />Whether or not nature is fundamentally 'really' continuous or whether that's just a good approximation nobody knows. When I say that quantum mechanics has continuous observables I am referring to the theories which we currently have, which do, in particular, treat space and time as continuous. <br /><br />There is actually a lot of discussion about the point which youSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-21005889556878717842016-04-09T01:49:20.947-04:002016-04-09T01:49:20.947-04:00Len,
One thing I should add - there is one except...Len,<br /><br />One thing I should add - there is one exception to what I said that the full system always remains in a pure state if it started in one, and that are black holes. If the environment contains a black hole, any part of the wavefunction that vanishes behind the horizon is ultimately destroyed in the singularity, converting a pure state into a mixed state not because you willingly Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-33856917350676582242016-04-09T01:46:16.094-04:002016-04-09T01:46:16.094-04:00Len,
You got that basically right. Decoherence co...Len,<br /><br />You got that basically right. Decoherence comes about because the system that you want to observe (say, the cat), becomes entangled with some other system (the air, the box, the measurement apparatus) - which you can generally think of as the environment. "Tracing out" essentially means you discard the information in the second system (on the rationale that you don'tSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-91515142051549646962016-04-09T01:30:25.792-04:002016-04-09T01:30:25.792-04:00Tom,
You fail to understand what decoherence is e...Tom,<br /><br />You fail to understand what decoherence is even good for. Also, you are putting words into my mouth I didn't use - I never said, not here and not elsewhere, that decoherence solves the measurement problem. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-26022034356213434842016-04-08T22:09:03.995-04:002016-04-08T22:09:03.995-04:00I don't know if someone has mentioned this art...I don't know if someone has mentioned this article to you before but this shows we can put things into super positions that are big enough for us to observe under a microscope. I would love to see what it does when they do this, sit still, or move, or some how both.<br />http://www.nature.com/news/2010/100317/full/news.2010.130.htmlAnonymoushttps://www.blogger.com/profile/11881269141412960346noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-968629095322023052016-04-08T21:01:13.570-04:002016-04-08T21:01:13.570-04:00Hi Bee,
Well, more praise from luboš:
"Ver...Hi Bee, <br /><br />Well, more praise from luboš:<br /><br />"Verdict<br /><br />Hossenfelder got 7 "totally correct" ratings, 3 "ambiguous" ones, and no "completely wrong" ones. This is better than what 90% of the people calling themselves "researchers in the quantum foundations" could ever achieve. ;-)"<br /><br />See: The Reference Frame: Nick Maiorinohttps://www.blogger.com/profile/12881730412761414391noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-79063176376902672462016-04-08T17:43:07.703-04:002016-04-08T17:43:07.703-04:00Schrödinger’s cat was a story created by Schröding...Schrödinger’s cat was a story created by Schrödinger to show how ridiculous QM was (and is). He would not be happy knowing that his cat story is now used to demonstrate QM. Sabine's modern take on the problem - decoherence - is not a defence for the measurement problem, its a head in the sand position. QM is linear and there is also no limit to the number of dimensions in Hilbert space. So Tom Andersenhttps://www.blogger.com/profile/17562906116020498110noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-44490393311052648062016-04-08T14:41:40.653-04:002016-04-08T14:41:40.653-04:00Bee,
Thank you for responding! "The purpose...Bee, <br /><br />Thank you for responding! "The purpose of my writing is to convey knowledge to those who don't have enough background to understand the equations." I appreciate it since I am one of those people. I do understand the interpretations are very different about what decoherence phenomenology is (the <a rel="nofollow">wikipedia</a> does a great job explaining it). <br />Lenhttps://www.blogger.com/profile/16449424046544947788noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-48415353630083558992016-04-08T11:47:21.240-04:002016-04-08T11:47:21.240-04:00Thanks for your reply. It makes sense to me if I s...Thanks for your reply. It makes sense to me if I summarize it correctly as follows: your statements refer to models of reality but not reality itself. So in the QM model there are things modeled as discrete and things modeled as continuous; and in the atomic lattice model electron position is modeled as continuous, although it may turn out (in the quantum gravity model which we do not yet have) JimVhttps://www.blogger.com/profile/10198704789965278981noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-84580761948418143182016-04-08T10:19:27.007-04:002016-04-08T10:19:27.007-04:00naivetheorist,
I commented on Tegmark's paper...naivetheorist,<br /><br /><a href="http://backreaction.blogspot.com/2014/05/consciousness-and-physics-from-scratch.html" rel="nofollow">I commented on Tegmark's paper here</a>. As you'll note I wasn't really convinced, but roughly speaking I think that this line of inquiry deserves more attention. I don't know what you think that I study that can't be experimentally falsified. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-71490980295022501302016-04-08T09:53:03.807-04:002016-04-08T09:53:03.807-04:00according to IIT (https://medium.com/the-physics-...according to IIT (https://medium.com/the-physics-arxiv-blog/why-physicists-are-saying-consciousness-is-a-state-of-matter-like-a-solid-a-liquid-or-a-gas-5e7ed624986d#.6ehjm1i3t), consciousness is... well, the IIT definition of consciousness is totally arbitrary and Tegmark's calculation of it is the sort of pseudo-scientific babbling you might expect form a tenured professor who can get awaynaivetheoristhttps://www.blogger.com/profile/00425164894020381981noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-78891455846455951492016-04-08T09:37:30.428-04:002016-04-08T09:37:30.428-04:00naivetheorist,
Indeed, as I wrote in the above bl...naivetheorist,<br /><br />Indeed, as I wrote in the above blogpost, first point "Everything is quantum". If the description of a system makes no use of quantum mechanics that's because it's an approximation. This applies to everything physical. I don't know what "consciousness" is. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-72593834528884079012016-04-08T09:29:49.196-04:002016-04-08T09:29:49.196-04:00"Yes, polymer chains are of course quantum me..."Yes, polymer chains are of course quantum mechanical." so i guess you think EVERYTHING is quantum mechanical, even though their description makes no use of quantum mechanical concepts or entities. does this also apply to consciousness (the mind, not the brain)?naivetheoristhttps://www.blogger.com/profile/00425164894020381981noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-9370629146214636202016-04-08T09:29:24.318-04:002016-04-08T09:29:24.318-04:00Maurice,
Decoherence reduces the off-diagonal ele...Maurice,<br /><br />Decoherence reduces the off-diagonal elements in the density matrix to an unmeasurably small number, which amounts to saying that we don't observe superpositions of the state being measured in the pointer basis. Those who know how decoherence works don't need your comment. And those who don't know won't find your comments useful either. Consequently, the only Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-49520511901572089262016-04-08T09:19:48.320-04:002016-04-08T09:19:48.320-04:00john,
I agree with your first point. About the se...john,<br /><br />I agree with your first point. About the second point: I am only referring to measurable entities. Sabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-1729095651686530652016-04-08T09:14:24.402-04:002016-04-08T09:14:24.402-04:00naivetheorist,
Yes, what I mean by "quantum ...naivetheorist,<br /><br />Yes, what I mean by "quantum mechanical" is "described by quantum mechanics". Discussions about what "exists" or doesn't exist are entirely superfluos for this. Yes, polymer chains are of course quantum mechanical. I have no idea what you mean by mathematics being the "instantiation of reality". I'm an instrumentalist. MathSabine Hossenfelderhttps://www.blogger.com/profile/06151209308084588985noreply@blogger.comtag:blogger.com,1999:blog-22973357.post-2457692098843076102016-04-08T09:08:09.028-04:002016-04-08T09:08:09.028-04:00I just disagree with a few (not many points); if y...I just disagree with a few (not many points); if you think about it you must conclude that the world is not only described by quantum mechanics, but that an extension and change of the Copenhagen rules is needed in order to accomodate democratically for the observer. Whether or not these rules are classical to some extend is unknown but there is certainly no proof whatsoever that large objects johnhttps://www.blogger.com/profile/06523031889979043404noreply@blogger.com