Posts Tagged ‘quantum mechanics’
“A nothing will serve just as well as a something about which nothing could be said”*…
Metaphysical debates in quantum physics don’t get at “truth,” physicist and mathematician Timothy Andersen argues; they’re nothing but a form of ritual activity and culture. After a thoughtful intellectual history of both quantum mechanics and Wittgenstein’s thought, he concludes…
If Wittgenstein were alive today, he might have couched his arguments in the vocabulary of cultural anthropology. For this shared grammar and these language games, in his view, form part of much larger ritualistic mechanisms that connect human activity with human knowledge, as deeply as DNA connects to human biology. It is also a perfect example of how evolution works by using pre-existing mechanisms to generate new behaviors.
The conclusion from all of this is that interpretation and representation in language and mathematics are little different than the supernatural explanations of ancient religions. Trying to resolve the debate between Bohr and Einstein is like trying to answer the Zen kōan about whether the tree falling in the forest makes a sound if no one can hear it. One cannot say definitely yes or no, because all human language must connect to human activity. And all human language and activity are ritual, signifying meaning by their interconnectedness. To ask what the wavefunction means without specifying an activity – and experiment – to extract that meaning is, therefore, as sensible as asking about the sound of the falling tree. It is nonsense.
As a scientist and mathematician, Wittgenstein has challenged my own tendency to seek out interpretations of phenomena that have no scientific value – and to see such explanations as nothing more than narratives. He taught that all that philosophy can do is remind us of what is evidently true. It’s evidently true that the wavefunction has a multiverse interpretation, but one must assume the multiverse first, since it cannot be measured. So the interpretation is a tautology, not a discovery.
I have humbled myself to the fact that we can’t justify clinging to one interpretation of reality over another. In place of my early enthusiastic Platonism, I have come to think of the world not as one filled with sharply defined truths, but rather as a place containing myriad possibilities – each of which, like the possibilities within the wavefunction itself, can be simultaneously true. Likewise, mathematics and its surrounding language don’t represent reality so much as serve as a trusty tool for helping people to navigate the world. They are of human origin and for human purposes.
To shut up and calculate, then, recognizes that there are limits to our pathways for understanding. Our only option as scientists is to look, predict and test. This might not be as glamorous an offering as the interpretations we can construct in our minds, but it is the royal road to real knowledge…
A provocative proposition: “Quantum Wittgenstein,” from @timcopia in @aeonmag.
* Ludwig Wittgenstein, Philosophical Investigations
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As we muse on meaning, we might recall that it was on this date in 1954 that the official ground-breaking for CERN (Conseil européen pour la recherche nucléaire) was held. Located in Switzerland, it is the largest particle physics laboratory in the world… that’s to say, a prime spot to do the observation and calculation that Andersen suggests. Indeed, it’s been the site of many breakthrough discoveries over the years, maybe most notably the 2012 observation of the Higgs Boson.
Because researchers need remote access to these facilities, the lab has historically been a major wide area network hub. Indeed, it was at CERN that Tim Berners-Lee developed the first “browser”– and effectively fomented the emergence of the web.
“Information was found to be everywhere”*…
A newly-proposed experiment could confirm the fifth state of matter in the universe—and change physics as we know it…
Physicist Dr. Melvin Vopson has already published research suggesting that information has mass and that all elementary particles, the smallest known building blocks of the universe, store information about themselves, similar to the way humans have DNA.
Now, he has designed an experiment—which if proved correct—means he will have discovered that information is the fifth form of matter, alongside solid, liquid, gas and plasma…
Dr. Vopson said: “This would be a eureka moment because it would change physics as we know it and expand our understanding of the universe. But it wouldn’t conflict with any of the existing laws of physics. It doesn’t contradict quantum mechanics, electrodynamics, thermodynamics or classical mechanics. All it does is complement physics with something new and incredibly exciting.”
Dr. Vopson’s previous research suggests that information is the fundamental building block of the universe and has physical mass. He even claims that information could be the elusive dark matter that makes up almost a third of the universe…
Is information is a key element of everything in the universe? “New experiment could confirm the fifth state of matter in the universe.”
* James Gleick, The Information: A History, a Theory, a Flood
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As we go deep, we might send thoroughly-modeled birthday greetings to Stanislaw Ulam; he was born on this date in 1909. A mathematician and nuclear physicist, he originated the Teller–Ulam design of thermonuclear weapons, discovered the concept of the cellular automaton, and suggested nuclear pulse propulsion.
But his most impactful contribution may have been his creation of the the Monte Carlo method of computation. While playing solitaire during his recovery from surgery, Ulam had thought about playing hundreds of games to estimate statistically the probability of a successful outcome. With ENIAC in mind, he realized that the availability of computers made such statistical methods very practical, and in 1949, he and Nicholas Metropolis published the first unclassified paper on the Monte Carlo method… which is now widely used in virtually every scientific field, in engineering and computer science, finance and business, and the law.
“I visualize a time when we will be to robots what dogs are to humans. And I am rooting for the machines.”*…
Readers will know of your correspondent’s fascination with the remarkable Claude Shannon (see here and here), remembered as “the father of information theory,” but seminally involved in so much more. In a recent piece in IEEE Spectrum, the redoubtable Rodney Brooks argues that we should add another credit to Shannon’s list…
Among the great engineers of the 20th century, who contributed the most to our 21st-century technologies? I say: Claude Shannon.
Shannon is best known for establishing the field of information theory. In a 1948 paper, one of the greatest in the history of engineering, he came up with a way of measuring the information content of a signal and calculating the maximum rate at which information could be reliably transmitted over any sort of communication channel. The article, titled “A Mathematical Theory of Communication,” describes the basis for all modern communications, including the wireless Internet on your smartphone and even an analog voice signal on a twisted-pair telephone landline. In 1966, the IEEE gave him its highest award, the Medal of Honor, for that work.
If information theory had been Shannon’s only accomplishment, it would have been enough to secure his place in the pantheon. But he did a lot more…
In 1950 Shannon published an article in Scientific American and also a research paper describing how to program a computer to play chess. He went into detail on how to design a program for an actual computer…
Shannon did all this at a time when there were fewer than 10 computers in the world. And they were all being used for numerical calculations. He began his research paper by speculating on all sorts of things that computers might be programmed to do beyond numerical calculations, including designing relay and switching circuits, designing electronic filters for communications, translating between human languages, and making logical deductions. Computers do all these things today…
The “father of information theory” also paved the way for AI: “How Claude Shannon Helped Kick-start Machine Learning,” from @rodneyabrooks in @IEEESpectrum.
* Claude Shannon (who may or may not have been kidding…)
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As we ponder possibility, we might send uncertain birthday greetings to Werner Karl Heisenberg; he was born on this date in 1901. A theoretical physicist, he made important contributions to the theories of the hydrodynamics of turbulent flows, the atomic nucleus, ferromagnetism, superconductivity, cosmic rays, and subatomic particles. But he is most widely remembered as a pioneer of quantum mechanics and author of what’s become known as the Heisenberg Uncertainty Principle. Heisenberg was awarded the Nobel Prize in Physics for 1932 “for the creation of quantum mechanics.”
During World War II, Heisenberg was part of the team attempting to create an atomic bomb for Germany– for which he was arrested and detained by the Allies at the end of the conflict. He was returned to Germany, where he became director of the Kaiser Wilhelm Institute for Physics, which soon thereafter was renamed the Max Planck Institute for Physics. He later served as president of the German Research Council, chairman of the Commission for Atomic Physics, chairman of the Nuclear Physics Working Group, and president of the Alexander von Humboldt Foundation.
Some things are so serious that one can only joke about them
Werner Heisenberg
“The threat of a pandemic is different from that of a nerve agent, in that a disease can spread uncontrollably, long after the first carrier has succumbed”*…
We were, of course, warned. As we do our best to digest the news of emergent new strains of the COVID-19 virus, a look back at Annie Sparrow‘s 2016 New York Review of Books essay on pandemics…
Pandemics—the uncontrolled spread of highly contagious diseases across countries and continents—are a modern phenomenon. The word itself, a neologism from Greek words for “all” and “people,” has been used only since the mid-nineteenth century. Epidemics—localized outbreaks of diseases—have always been part of human history, but pandemics require a minimum density of population and an effective means of transport. Since “Spanish” flu burst from the trenches of World War I in 1918, infecting 20 percent of the world’s population and killing upward of 50 million people, fears of a similar pandemic have preoccupied public health practitioners, politicians, and philanthropists. World War II, in which the German army deliberately caused malaria epidemics and the Japanese experimented with anthrax and plague as biological weapons, created new fears…
According to the doctor, writer, and philanthropist Larry Brilliant, “outbreaks are inevitable, pandemics are optional.”
…
Much of human history can be seen as a struggle for survival between humans and microbes. Pandemics are microbe offensives; public health measures are human defenses. Water purification, sanitation, and vaccination are crucial to our living longer, better, even taller lives. But these measures of mass salvation are not sexy. While we know prevention is better and considerably cheaper than cure, there is little financial reward or glory in it. Philanthropists prefer to build hospitals rather than pay community health workers. Pharmaceutical companies prefer the Western market to the distant and poor Global South where people cannot afford to buy treatments. Education is a powerful social vaccine against the ignorance that enables pathogens to flourish, but insufficient to overcome the corruption of public goods by private interests. The current enthusiasm for detecting the next panic-inducing pathogen should not divert resources and research from the perennial threats that we already have. We must resist the tendency of familiarity and past failures to encourage contempt and indifference…
An important (and in its time, sadly, prescient) read: “The Awful Diseases on the Way,” from @annie_sparrow in @nybooks.
See also “6 of the Worst Pandemics in History” (source of the image above) and “A history of pandemics.”
[TotH to MK]
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As we prioritize preparation, we might recall that it was on this date in 1935 that physicist Erwin Schrödinger published his famous thought experiment– now known as “Schrödinger’s cat“– a paradox that illustrates the problem of the Copenhagen interpretation of quantum mechanics.
“It can be argued that in trying to see behind the formal predictions of quantum theory we are just making trouble for ourselves”*…
Context, it seems, is everthing…
… What is reality? Nope. There’s no way we are going through that philosophical minefield. Let’s focus instead on scientific realism, the idea that a world of things exists independent of the minds that might perceive it and it is the world slowly revealed by progress in science. Scientific realism is the belief that the true nature of reality is the subject of scientific investigation and while we may not completely understand it at any given moment, each experiment gets us a little bit closer. This is a popular philosophical position among scientists and science enthusiasts.
A typical scientific realist might believe, for example, that fundamental particles exist even though we cannot perceive them directly with our senses. Particles are real and their properties — whatever they may be — form part of the state of the world. A slightly more extreme view is that this state of the world can be specified with mathematical quantities and these, in turn, obey equations we call physical laws. In this view, the ultimate goal of science is to discover these laws. So what are the consequences of quantum physics on these views?
As I mentioned above, quantum physics is not a realistic model of the world — that is, it does not specify quantities for states of the world. An obvious question is then can we supplement or otherwise replace quantum physics with a deeper set of laws about real states of the world? This is the question Einstein first asked with colleagues Podolski and Rosen, making headlines in 1935. The hypothetical real states of the world came to be called hidden variables since an experiment does not reveal them — at least not yet.
In the decades that followed quantum physics rapidly turned into applied science and the textbooks which became canon demonstrated only how to use the recipes of quantum physics. In textbooks that are still used today, no mention is made of the progress in the foundational aspects of quantum physics since the mathematics was cemented almost one hundred years ago. But, in the 1960s, the most important and fundamental aspect of quantum physics was discovered and it put serious restrictions on scientific realism. Some go as far as to say the entire nature of independent reality is questionable due to it. What was discovered is now called contextuality, and its inevitability is referred to as the Bell-Kochen-Specker theorem.
John Bell is the most famous of the trio Bell, Kochen, and Specker, and is credited with proving that quantum physics contained so-called nonlocal correlations, a consequence of quantum entanglement. Feel free to read about those over here.
It was Bell’s ideas and notions that stuck and eventually led to popular quantum phenomena such as teleportation. Nonlocality itself is wildly popular these days in science magazines with reported testing of the concept in delicately engineered experiments that span continents and sometimes involve research satellites. But nonlocality is just one type of contextuality, which is the real game in town.
In the most succinct sentence possible, contextuality is the name for the fact that any real states of the world giving rise to the rules of quantum physics must depend on contexts that no experiment can distinguish. That’s a lot to unpack. Remember that there are lots of ways to prepare the same experiment — and by the same experiment, I mean many different experiments with completely indistinguishable results. Doing the exact same thing as yesterday in the lab, but having had a different breakfast, will give the same experimental results. But there are things in the lab and very close to the system under investigation that don’t seem to affect the results either. An example might be mixing laser light in two different ways.
There are different types of laser light that, once mixed together, are completely indistinguishable from one another no matter what experiments are performed on the mixtures. You could spend a trillion dollars on scientific equipment and never be able to tell the two mixtures apart. Moreover, knowing only the resultant mixture — and not the way it was mixed — is sufficient to accurately predict the outcomes of any experiment performed with the light. So, in quantum physics, the mathematical theory has a variable that refers to the mixture and not the way the mixture was made — it’s Occam’s razor in practice.
Now let’s try to invent a deeper theory of reality underpinning quantum physics. Surely, if we are going to respect Occam’s razor, the states in our model should only depend on contexts with observable consequences, right? If there is no possible experiment that can distinguish how the laser light is mixed, then the underlying state of reality should only depend on the mixture and not the context in which it was made, which, remember, might include my breakfast choices. Alas, this is just not possible in quantum physics — it’s a mathematical impossibility in the theory and has been confirmed by many experiments.
So, does this mean the universe cares about what I have for breakfast? Not necessarily. But, to believe the universe doesn’t care what I had for breakfast means you must also give up reality. You may be inclined to believe that when you observe something in the world, you are passively looking at it just the way it would have been had you not been there. But quantum contextuality rules this out. There is no way to define a reality that is independent of the way we choose to look at it…
“Why is no one taught the one concept in quantum physics which denies reality?” It’s called contextuality and it is the essence of quantum physics. From Chris Ferrie (@csferrie).
* “It can be argued that in trying to see behind the formal predictions of quantum theory we are just making trouble for ourselves. Was not precisely this the lesson that had to be learned before quantum mechanics could be constructed, that it is futile to try to see behind the observed phenomena?” – John Stewart Bell
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As still we try, we might relatively hearty birthday greetings to Sir Marcus Laurence Elwin “Mark” Oliphant; he was born on this date in 1901. An Australian physicist who trained and did much of his work in England (where he studied under Sir Ernest Rutherford at the University of Cambridge’s Cavendish Laboratory), Oliphant was deeply involved in the Allied war effort during World War II. He helped develop microwave radar, and– by helping to start the Manhattan Project and then working with his friend Ernest Lawrence at the Radiation Laboratory in Berkeley, California, helped develop the atomic bomb.
After the war, Oliphant returned to Australia as the first director of the Research School of Physical Sciences and Engineering at the new Australian National University (ANU); on his retirement, he became Governor of South Australia and helped found the Australian Democrats political party.
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