Posts Tagged ‘quantum theory’
“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.
“Men knew better than they realized, when they placed the abode of the gods beyond the reach of gravity”*…
In search of a theory of everything…
Twenty-five particles and four forces. That description — the Standard Model of particle physics — constitutes physicists’ best current explanation for everything. It’s neat and it’s simple, but no one is entirely happy with it. What irritates physicists most is that one of the forces — gravity — sticks out like a sore thumb on a four-fingered hand. Gravity is different.
Unlike the electromagnetic force and the strong and weak nuclear forces, gravity is not a quantum theory. This isn’t only aesthetically unpleasing, it’s also a mathematical headache. We know that particles have both quantum properties and gravitational fields, so the gravitational field should have quantum properties like the particles that cause it. But a theory of quantum gravity has been hard to come by.
In the 1960s, Richard Feynman and Bryce DeWitt set out to quantize gravity using the same techniques that had successfully transformed electromagnetism into the quantum theory called quantum electrodynamics. Unfortunately, when applied to gravity, the known techniques resulted in a theory that, when extrapolated to high energies, was plagued by an infinite number of infinities. This quantization of gravity was thought incurably sick, an approximation useful only when gravity is weak.
Since then, physicists have made several other attempts at quantizing gravity in the hope of finding a theory that would also work when gravity is strong. String theory, loop quantum gravity, causal dynamical triangulation and a few others have been aimed toward that goal. So far, none of these theories has experimental evidence speaking for it. Each has mathematical pros and cons, and no convergence seems in sight. But while these approaches were competing for attention, an old rival has caught up.
The theory called asymptotically (as-em-TOT-ick-lee) safe gravity was proposed in 1978 by Steven Weinberg. Weinberg, who would only a year later share the Nobel Prize with Sheldon Lee Glashow and Abdus Salam for unifying the electromagnetic and weak nuclear force, realized that the troubles with the naive quantization of gravity are not a death knell for the theory. Even though it looks like the theory breaks down when extrapolated to high energies, this breakdown might never come to pass. But to be able to tell just what happens, researchers had to wait for new mathematical methods that have only recently become available…
For decades, physicists have struggled to create a quantum theory of gravity. Now an approach that dates to the 1970s is attracting newfound attention: “Why an Old Theory of Everything Is Gaining New Life,” from @QuantaMagazine.
* Arthur C. Clarke, 2010: Odyssey Two
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As we unify, we might pause to remember Sir Arthur Stanley Eddington, OM, FRS; he died in this date in 1944. An astrophysicist, mathematician, and philosopher of science known for his work on the motion, distribution, evolution and structure of stars, Eddington is probably best remembered for his relationship to Einstein: he was, via a series of widely-published articles, the primary “explainer” of Einstein’s Theory of General Relativity to the English-speaking world; and he was, in 1919, the leader of the experimental team that used observations of a solar eclipse to confirm the theory.
“The past, like the future, is indefinite and exists only as a spectrum of possibilities”*…
A recent paper by Robert Lanza and others suggests that physical reality isn’t independent of us, “objective,” but is the product of networks of observers…
Is there physical reality that is independent of us? Does objective reality exist at all? Or is the structure of everything, including time and space, created by the perceptions of those observing it? Such is the groundbreaking assertion of a new paper published in the Journal of Cosmology and Astroparticle Physics.
The paper’s authors include Robert Lanza, a stem cell and regenerative medicine expert, famous for the theory of biocentrism, which argues that consciousness is the driving force for the existence of the universe. He believes that the physical world that we perceive is not something that’s separate from us but rather created by our minds as we observe it. According to his biocentric view, space and time are a byproduct of the “whirl of information” in our head that is weaved together by our mind into a coherent experience.
His new paper, co-authored by Dmitriy Podolskiy and Andrei Barvinsky, theorists in quantum gravity and quantum cosmology, shows how observers influence the structure of our reality.
According to Lanza and his colleagues, observers can dramatically affect “the behavior of observable quantities” both at microscopic and massive spatiotemporal scales. In fact, a “profound shift in our ordinary everyday worldview” is necessary, wrote Lanza in an interview with Big Think. The world is not something that is formed outside of us, simply existing on its own. “Observers ultimately define the structure of physical reality itself,” he stated.
How does this work? Lanza contends that a network of observers is necessary and is “inherent to the structure of reality.” As he explains, observers — you, me, and anyone else — live in a quantum gravitational universe and come up with “a globally agreed-upon cognitive model” of reality by exchanging information about the properties of spacetime. “For, once you measure something,” Lanza writes, “the wave of probability to measure the same value of the already probed physical quantity becomes ‘localized’ or simply ‘collapses.’” That’s how reality comes to be consistently real to us all. Once you keep measuring a quantity over and over, knowing the result of the first measurement, you will see the outcome to be the same.
“Similarly, if you learn from somebody about the outcomes of their measurements of a physical quantity, your measurements and those of other observers influence each other ‒ freezing the reality according to that consensus,” added Lanza, explaining further that “a consensus of different opinions regarding the structure of reality defines its very form, shaping the underlying quantum foam,” explained Lanza.
In quantum terms, an observer influences reality through decoherence, which provides the framework for collapsing waves of probability, “largely localized in the vicinity of the cognitive model which the observer builds in their mind throughout their lifespan,” he added.
Lanza says, “The observer is the first cause, the vital force that collapses not only the present, but the cascade of spatiotemporal events we call the past. Stephen Hawking was right when he said: ‘The past, like the future, is indefinite and exists only as a spectrum of possibilities.’”
Could an artificially intelligent entity without consciousness be dreaming up our world? Lanza believes biology plays an important role, as he explains in his book The Grand Biocentric Design: How Life Creates Reality, which he co-authored with the physicist Matej Pavsic.
While a bot could conceivably be an observer, Lanza thinks a conscious living entity with the capacity for memory is necessary to establish the arrow of time. “‘A brainless’ observer does not experience time and/or decoherence with any degree of freedom,” writes Lanza. This leads to the cause and effect relationships we can notice around us. Lanza thinks that “we can only say for sure that a conscious observer does indeed collapse a quantum wave function.”…
Another key aspect of their work is that it resolves “the exasperating incompatibility between quantum mechanics and general relativity,” which was a sticking point even for Albert Einstein.
The seeming incongruity of these two explanations of our physical world — with quantum mechanics looking at the molecular and subatomic levels and general relativity at the interactions between massive cosmic structures like galaxies and black holes — disappears once the properties of observers are taken into account.
While this all may sound speculative, Lanza says their ideas are being tested using Monte Carlo simulations on powerful MIT computer clusters and will soon be tested experimentally.
Is the physical universe independent from us, or is it created by our minds? “Is human consciousness creating reality?” @RobertLanza
We might wonder, if this is so, how reality emerged at all. Perhaps one possibility is implied in “Consciousness was upon him before he could get out of the way.”
* Stephen Hawking
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As we conjure with consciousness, we might recall that it was on this date in 1908 (the same year that he was awarded the Nobel Prize in Physics) that Ernest Rutherford announced in London that he had isolated a single atom of matter. The following year, he, Hans Geiger (later of “counter” fame), and Ernest Marsden conducted the “Gold Foil Experiment,” the results of which replaced J. J. Thomson‘s “Plum Pudding Model” of the atom with what became known as the “Rutherford Model“: a very small charged nucleus, containing much of the atom’s mass, orbited by low-mass electrons.
“Bohr was inconsistent, unclear, willfully obscure, and right. Einstein was consistent, clear, down-to-earth, and wrong.”*…
The founders of quantum mechanics understood it to be deeply, profoundly weird. Albert Einstein, for one, went to his grave convinced that the theory had to be just a steppingstone to a more complete description of nature, one that would do away with the disturbing quirks of the quantum.
Then in 1964, John Stewart Bell proved a theorem that would test whether quantum theory was obscuring a full description of reality, as Einstein claimed. Experimenters have since used Bell’s theorem to rule out the possibility that beneath all the apparent quantum craziness — the randomness and the spooky action at a distance — is a hidden deterministic reality that obeys the laws of relativity.
Now a new theorem has taken Bell’s work a step further. The theorem makes some reasonable-sounding assumptions about physical reality. It then shows that if a certain experiment were carried out — one that is, to be fair, extravagantly complicated — the expected results according to the rules of quantum theory would force us to reject one of those assumptions.
According to Matthew Leifer, a quantum physicist at Chapman University who did not participate in the research, the new work focuses attention on a class of interpretations of quantum mechanics that until now have managed to escape serious scrutiny from similar “no-go” theorems.
Broadly speaking, these interpretations argue that quantum states reflect our own knowledge of physical reality, rather than being faithful representations of something that exists out in the world. The exemplar of this group of ideas is the Copenhagen interpretation, the textbook version of quantum theory, which is most popularly understood to suggest that particles don’t have definite properties until those properties are measured. Other Copenhagen-like quantum interpretations go even further, characterizing quantum states as subjective to each observer…
… which has, as you will see as you read on in the piece excerpted above, some pretty profoundly weird implications. Either the rules of quantum mechanics don’t always apply, or at least one basic assumption about reality must be wrong: “A New Theorem Maps Out the Limits of Quantum Physics.”
See also “Reality is that which, when you stop believing in it, doesn’t go away.”
* John Stewart Bell
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As we pity Schrödinger’s cat, we might we might send penetrating birthday greetings to Henry Way Kendall; he was born on this date in 1926. A particle physicist, he shared the Nobel Prize in Physics in 1990 (with Jerome Isaac Friedman and Richard E. Taylor) “for their pioneering investigations concerning deep inelastic scattering of electrons on protons and bound neutrons, which have been of essential importance for the development of the quark model in particle physics.”
In 1969, Kendall helped found the Union of Concerned Scientists. In 1997, in connection with the Kyoto Climate Summit, he helped produce a statement signed by 2,000 scientists calling for action on global warming.
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