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It;s ironic that the outcome of this would be to objectively prove the subjectivity of science :-) Cheers, John On Sun, Nov 17, 2019 at 4:53 AM Louis Proyect via Marxism < [email protected]> wrote: > ******************** POSTING RULES & NOTES ******************** > #1 YOU MUST clip all extraneous text when replying to a message. > #2 This mail-list, like most, is publicly & permanently archived. > #3 Subscribe and post under an alias if #2 is a concern. > ***************************************************************** > > On 11/16/19 10:19 AM, Marla Vijaya kumar via Marxism wrote: > > > > Louis, The subject is extremely interesting and I am working > on the philosophical aspect of it. > > But unfortunately, it requires subscription. > > Can you post the text? > > Vijaya Kumar M > > Vijaya, this was from Alternet, which does not have paywalls. In any case: > > Quantum physics: our study suggests objective reality doesn’t exist > November 14, 2019 7.40am EST > > Authors > Alessandro Fedrizzi > Professor of Quantum Physics, Heriot-Watt University > > Massimiliano Proietti > PhD Candidate of Quantum Physics, Heriot-Watt University > > Alternative facts are spreading like a virus across society. Now it > seems they have even infected science – at least the quantum realm. This > may seem counter intuitive. The scientific method is after all founded > on the reliable notions of observation, measurement and repeatability. A > fact, as established by a measurement, should be objective, such that > all observers can agree with it. > > But in a paper recently published in Science Advances, we show that, in > the micro-world of atoms and particles that is governed by the strange > rules of quantum mechanics, two different observers are entitled to > their own facts. In other words, according to our best theory of the > building blocks of nature itself, facts can actually be subjective. > > Observers are powerful players in the quantum world. According to the > theory, particles can be in several places or states at once – this is > called a superposition. But oddly, this is only the case when they > aren’t observed. The second you observe a quantum system, it picks a > specific location or state – breaking the superposition. The fact that > nature behaves this way has been proven multiple times in the lab – for > example, in the famous double slit experiment (see video below). > > > In 1961, physicist Eugene Wigner proposed a provocative thought > experiment. He questioned what would happen when applying quantum > mechanics to an observer that is themselves being observed. Imagine that > a friend of Wigner tosses a quantum coin – which is in a superposition > of both heads and tails – inside a closed laboratory. Every time the > friend tosses the coin, they observe a definite outcome. We can say that > Wigner’s friend establishes a fact: the result of the coin toss is > definitely head or tail. > > Wigner doesn’t have access to this fact from the outside, and according > to quantum mechanics, must describe the friend and the coin to be in a > superposition of all possible outcomes of the experiment. That’s because > they are “entangled” – spookily connected so that if you manipulate one > you also manipulate the other. Wigner can now in principle verify this > superposition using a so-called “interference experiment” – a type of > quantum measurement that allows you to unravel the superposition of an > entire system, confirming that two objects are entangled. > > When Wigner and the friend compare notes later on, the friend will > insist they saw definite outcomes for each coin toss. Wigner, however, > will disagree whenever he observed friend and coin in a superposition. > > This presents a conundrum. The reality perceived by the friend cannot be > reconciled with the reality on the outside. Wigner originally didn’t > consider this much of a paradox, he argued it would be absurd to > describe a conscious observer as a quantum object. However, he later > departed from this view, and according to formal textbooks on quantum > mechanics, the description is perfectly valid. > > The experiment > The scenario has long remained an interesting thought experiment. But > does it reflect reality? Scientifically, there has been little progress > on this until very recently, when Časlav Brukner at the University of > Vienna showed that, under certain assumptions, Wigner’s idea can be used > to formally prove that measurements in quantum mechanics are subjective > to observers. > > Brukner proposed a way of testing this notion by translating the > Wigner’s friend scenario into a framework first established by the > physicist John Bell in 1964. Brukner considered two pairs of Wigners and > friends, in two separate boxes, conducting measurements on a shared > state – inside and outside their respective box. The results can be > summed up to ultimately be used to evaluate a so called “Bell > inequality”. If this inequality is violated, observers could have > alternative facts. > > We have now for the first time performed this test experimentally at > Heriot-Watt University in Edinburgh on a small-scale quantum computer > made up of three pairs of entangled photons. The first photon pair > represents the coins, and the other two are used to perform the coin > toss – measuring the polarisation of the photons – inside their > respective box. Outside the two boxes, two photons remain on each side > that can also be measured. > > > Researchers with experiment. Author provided > Despite using state-of-the-art quantum technology, it took weeks to > collect sufficient data from just six photons to generate enough > statistics. But eventually, we succeeded in showing that quantum > mechanics might indeed be incompatible with the assumption of objective > facts – we violated the inequality. > > The theory, however, is based on a few assumptions. These include that > the measurement outcomes are not influenced by signals travelling above > light speed and that observers are free to choose what measurements to > make. That may or may not be the case. > > Another important question is whether single photons can be considered > to be observers. In Brukner’s theory proposal, observers do not need to > be conscious, they must merely be able to establish facts in the form of > a measurement outcome. An inanimate detector would therefore be a valid > observer. And textbook quantum mechanics gives us no reason to believe > that a detector, which can be made as small as a few atoms, should not > be described as a quantum object just like a photon. It may also be > possible that standard quantum mechanics does not apply at large length > scales, but testing that is a separate problem. > > > There may be many worlds out there. Nikk/Flickr, CC BY-SA > This experiment therefore shows that, at least for local models of > quantum mechanics, we need to rethink our notion of objectivity. The > facts we experience in our macroscopic world appear to remain safe, but > a major question arises over how existing interpretations of quantum > mechanics can accommodate subjective facts. > > Some physicists see these new developments as bolstering interpretations > that allow more than one outcome to occur for an observation, for > example the existence of parallel universes in which each outcome > happens. Others see it as compelling evidence for intrinsically > observer-dependent theories such as Quantum Bayesianism, in which an > agent’s actions and experiences are central concerns of the theory. But > yet others take this as a strong pointer that perhaps quantum mechanics > will break down above certain complexity scales. > > Clearly these are all deeply philosophical questions about the > fundamental nature of reality. Whatever the answer, an interesting > future awaits. > _________________________________________________________ > Full posting guidelines at: http://www.marxmail.org/sub.htm > Set your options at: > https://lists.csbs.utah.edu/options/marxism/johnedmundson4%40gmail.com -- The law locks up the man or woman Who steals the goose from off the common But leaves the greater villain loose Who steals the common from the goose _________________________________________________________ Full posting guidelines at: http://www.marxmail.org/sub.htm Set your options at: https://lists.csbs.utah.edu/options/marxism/archive%40mail-archive.com
