[Marxism] Quantum Experiment
johnedmundson4 at gmail.com
Sat Nov 16 13:47:13 MST 2019
It;s ironic that the outcome of this would be to objectively prove the
subjectivity of science :-)
On Sun, Nov 17, 2019 at 4:53 AM Louis Proyect via Marxism <
marxism at lists.csbs.utah.edu> wrote:
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> 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
> 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.
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