Posts Tagged ‘quantum theory’
“How many general-relativity theorists does it take to change a light bulb?”*…
Jokes are where one finds them…
Heisenberg, Schrodinger, and Ohm are driving along the road together – Heisenberg is driving. After a time, they are stopped by a traffic cop. Heisenberg pulls over, and the cop comes up to the driver’s window.
“Sir, do you know how fast you were driving?” asks the cop.
“No” replies Heisenberg “but I know precisely where I am”
“You were doing 70.” says the cop
“Great!” says Heisenberg “Now we’re lost!”
The cop thinks this is very strange behaviour and so he decides to inspect the vehicle. After a time he comes back to the driver’s window and says
“Do you know there’s a dead cat in the trunk?”
“Well, now we do!!” yells Schrodinger.
The cop thinks this is all too weird, so he proceeds to arrest the three. Ohm resists.
source
[Image above: source]
* “How many general-relativity theorists does it take to change a light bulb? Two: one to hold the bulb and one to rotate space.” (source)
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As we chortle, we might spare a thought for Louis de Broglie (or as he was known more officially, Louis Victor Pierre Raymond, 7th Duc de Broglie); he died on this date in 1987. An aristocrat and physicist, he made significant contributions to quantum theory. In his 1924 PhD thesis, he postulated the wave nature of electrons and suggested that all matter has wave properties— a concept known as the de Broglie hypothesis, an example of wave–particle duality— a topic that occupied both Heisenberg and Schrodinger and that forms a central part of the theory of quantum mechanics. After the wave-like behavior of matter was first experimentally demonstrated in 1927, de Broglie won the Nobel Prize for Physics (in 1929).
Louis de Broglie was the sixteenth member elected to occupy seat 1 of the Académie française in 1944, and served as Perpetual Secretary of the French Academy of Sciences. He was the first high-level scientist to call for establishment of a multi-national laboratory, a proposal that led to the establishment of the European Organization for Nuclear Research (CERN).
“There is nothing new to be discovered in physics now. All that remains is more and more precise measurement.”*…
Some observations are best considered “interesting, if true”; some, a la Karl Popper, “true, until false”… Consider this very recent paper in Nature…
Theories of scientific and technological change view discovery and invention as endogenous processes, wherein previous accumulated knowledge enables future progress by allowing researchers to, in Newton’s words, ‘stand on the shoulders of giants.’ Recent decades have witnessed exponential growth in the volume of new scientific and technological knowledge, thereby creating conditions that should be ripe for major advances. Yet contrary to this view, studies suggest that progress is slowing in several major fields. Here, we analyse these claims at scale across six decades, using data on 45 million papers and 3.9 million patents from six large-scale datasets, together with a new quantitative metric—the CD index—that characterizes how papers and patents change networks of citations in science and technology. We find that papers and patents are increasingly less likely to break with the past in ways that push science and technology in new directions. This pattern holds universally across fields and is robust across multiple different citation- and text-based metrics. Subsequently, we link this decline in disruptiveness to a narrowing in the use of previous knowledge, allowing us to reconcile the patterns we observe with the ‘shoulders of giants’ view. We find that the observed declines are unlikely to be driven by changes in the quality of published science, citation practices or field-specific factors. Overall, our results suggest that slowing rates of disruption may reflect a fundamental shift in the nature of science and technology.
The full paper: “Papers and patents are becoming less disruptive over time” @Nature
One notes that the quote above– from Lord Kelvin, at the turn of the twentieth century– immediately preceded a couple of decades in which physics was radically redefined and advanced by Planck, Einstein, Bohr, et al. (In fairness to Kelvin, consider this suggestion that his point was more subtle.) As we look forward, we might ponder the ways in which the reorganization of disciplines, the rise of research in other cultures (less constrained by the mores of “conventional” research), the use of AI, and/or some as yet unknown dynamic could challenge the phenomenon– “a narrowing in the use of previous knowledge”– to which the authors attribute diminishing disruption.
[Source of the image above]
* Lord Kelvin, in an address to the the Royal Institution in April of 1900
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As we ponder progress, we might send advanced birthday greetings to Wilhelm Wien; he was born on this date in 1864. A physicist, his work helped move past Kelvin’s log-jam. In 1893, he used theories about heat and electromagnetism to deduce Wien’s displacement law, which calculates the emission of a blackbody (a surface that absorbs all radiant energy falling on it) at any temperature from the emission at any one reference temperature. His colleague Max Planck colaborated with Wien, then extended the thinking in what we now know as Planck’s law, which led to the development of quantum theory.
Wien received the 1911 Nobel Prize for his work on heat radiation.
Just before Kelvin’s speech (in 1898) Wien identified a positive particle equal in mass to the hydrogen atom– what we now know as a proton. Wien, in the techniques he used, laid the foundation of mass spectrometry.
“The ‘paradox’ is only a conflict between reality and your feeling of what reality ‘ought to be’”*…
Elegant experiments with entangled light have laid bare a profound mystery at the heart of reality. Daniel Garisto explains the importance of the work done by this year’s Nobel laureates in Physics…
One of the more unsettling discoveries in the past half century is that the universe is not locally real. “Real,” meaning that objects have definite properties independent of observation—an apple can be red even when no one is looking; “local” means objects can only be influenced by their surroundings, and that any influence cannot travel faster than light. Investigations at the frontiers of quantum physics have found that these things cannot both be true. Instead, the evidence shows objects are not influenced solely by their surroundings and they may also lack definite properties prior to measurement. As Albert Einstein famously bemoaned to a friend, “Do you really believe the moon is not there when you are not looking at it?”
This is, of course, deeply contrary to our everyday experiences. To paraphrase Douglas Adams, the demise of local realism has made a lot of people very angry and been widely regarded as a bad move.
Blame for this achievement has now been laid squarely on the shoulders of three physicists: John Clauser, Alain Aspect and Anton Zeilinger. They equally split the 2022 Nobel Prize in Physics “for experiments with entangled photons, establishing the violation of Bell inequalities and pioneering quantum information science.” (“Bell inequalities” refers to the pioneering work of the Northern Irish physicist John Stewart Bell, who laid the foundations for this year’s Physics Nobel in the early 1960s.) Colleagues agreed that the trio had it coming, deserving this reckoning for overthrowing reality as we know it. “It is fantastic news. It was long overdue,” says Sandu Popescu, a quantum physicist at the University of Bristol. “Without any doubt, the prize is well-deserved.”
“The experiments beginning with the earliest one of Clauser and continuing along, show that this stuff isn’t just philosophical, it’s real—and like other real things, potentially useful,” says Charles Bennett, an eminent quantum researcher at IBM…
Quantum foundations’ journey from fringe to favor was a long one. From about 1940 until as late as 1990, the topic was often treated as philosophy at best and crackpottery at worst. Many scientific journals refused to publish papers in quantum foundations, and academic positions indulging such investigations were nearly impossible to come by…
Today, quantum information science is among the most vibrant and impactful subfields in all of physics. It links Einstein’s general theory of relativity with quantum mechanics via the still-mysterious behavior of black holes. It dictates the design and function of quantum sensors, which are increasingly being used to study everything from earthquakes to dark matter. And it clarifies the often-confusing nature of quantum entanglement, a phenomenon that is pivotal to modern materials science and that lies at the heart of quantum computing…
Eminently worth reading in full: “The Universe Is Not Locally Real, and the Physics Nobel Prize Winners Proved It,” from @dangaristo in @sciam.
Apposite: entangled particles and wormholes could be manifestations of the same phenomenon, and resolve paradoxes like information escaping a black hole: “Black Holes May Hide a Mind-Bending Secret About Our Universe.”
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As we rethink reality, we might spare a thought for Walter Brattain; he died on this date in 1987. A physicist (at Bell Labs at the time), he worked with John Bardeen and William Shockley to invent the point-contact transistor in 1947, the birth of the semiconductor– work for which the trio shared the Nobel Prize in Physics in 1956.
At college, Brattain said, he majored in physics and math because they were the only subjects he was good at. He became a solid physicist with a good understanding of theory, but his strength was in physically constructing experiments. Working with the ideas of Shockley and Bardeen, Brattain’s hands built the first transistor. Shortly, the transistor replaced the bulkier vacuum tube for many uses and was the forerunner of microminiature electronic parts.
As semiconductor technology has advanced, it has begun to incorporate quantum effects.
“‘Space-time’ – that hideous hybrid whose very hyphen looks phoney”*…
Space and time seem about as basic as anything could be, even after Einstein’s theory of General Relativity threw (in) a curve. But as Steven Strogatz discusses with Sean Carroll, the reconciliation of Einstein’s work with quantum theory is seeming to suggest that space and time might actually be emergent properties of quantum reality, not fundamental parts of it…
… we’re going to be discussing the mysteries of space and time, and gravity, too. What’s so mysterious about them?
Well, it turns out they get really weird when we look at them at their deepest levels, at a super subatomic scale, where the quantum nature of gravity starts to kick in and become crucial. Of course, none of us have any direct experience with space and time and gravity at this unbelievably small scale. Up here, at the scale of everyday life, space and time seem perfectly smooth and continuous. And gravity is very well described by Isaac Newton’s classic theory, a theory that’s been around for over 300 years now.
But then, about 100 years ago, things started to get strange. Albert Einstein taught us that space and time could warp and bend like a piece of fabric. This warping of the space-time continuum is what we experience as gravity. But Einstein’s theory is mainly concerned with the largest scales of nature, the scale of stars, galaxies and the whole universe. It doesn’t really have much to say about space and time at the very smallest scales.
And that’s where the trouble really starts. Down there, nature is governed by quantum mechanics. This amazingly powerful theory has been shown to account for all the forces of nature, except gravity. When physicists try to apply quantum theory to gravity, they find that space and time become almost unrecognizable. They seem to start fluctuating wildly. It’s almost like space and time fall apart. Their smoothness breaks down completely, and that’s totally incompatible with the picture in Einstein’s theory.
s physicists try to make sense of all of this, some of them are coming to the conclusion that space and time may not be as fundamental as we always imagined. They’re starting to seem more like byproducts of something even deeper, something unfamiliar and quantum mechanical. But what could that something be?….
Find out at: “Where Do Space, Time and Gravity Come From?, ” from @stevenstrogatz and @seanmcarroll in @QuantaMagazine.
* Vladimir Nabokov
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As we fumble with the fundamental, we might send far-sighted birthday greetings to Jocelyn Bell Burnell; she was born on this date in 1943. An astrophysicist, she discovered the first pulsar, while working as a post-doc, in 1957. She then discovered the next three detected pulsars.
The discovery eventually earned the Nobel Prize in Physics in 1974; however, she was not one of the prize’s recipients. The paper announcing the discovery of pulsars had five authors. Bell’s thesis supervisor Antony Hewish was listed first, Bell second. Hewish was awarded the Nobel Prize, along with the astronomer Martin Ryle.
A pulsar— or pulsating radio star– a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. The precise periods of pulsars make them very useful tools. Observations of a pulsar in a binary neutron star system were used to confirm (indirectly) the existence of gravitational radiation. The first extrasolar planets were discovered around a pulsar, PSR B1257+12. And certain types of pulsars rival atomic clocks in their accuracy in keeping time.
“Nothing in life is certain except death, taxes and the second law of thermodynamics”*…
The second law of thermodynamics– asserting that the entropy of a system increases with time– is among the most sacred in all of science, but it has always rested on 19th century arguments about probability. As Philip Ball reports, new thinking traces its true source to the flows of quantum information…
In all of physical law, there’s arguably no principle more sacrosanct than the second law of thermodynamics — the notion that entropy, a measure of disorder, will always stay the same or increase. “If someone points out to you that your pet theory of the universe is in disagreement with Maxwell’s equations — then so much the worse for Maxwell’s equations,” wrote the British astrophysicist Arthur Eddington in his 1928 book The Nature of the Physical World. “If it is found to be contradicted by observation — well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.” No violation of this law has ever been observed, nor is any expected.
But something about the second law troubles physicists. Some are not convinced that we understand it properly or that its foundations are firm. Although it’s called a law, it’s usually regarded as merely probabilistic: It stipulates that the outcome of any process will be the most probable one (which effectively means the outcome is inevitable given the numbers involved).
Yet physicists don’t just want descriptions of what will probably happen. “We like laws of physics to be exact,” said the physicist Chiara Marletto of the University of Oxford. Can the second law be tightened up into more than just a statement of likelihoods?
A number of independent groups appear to have done just that. They may have woven the second law out of the fundamental principles of quantum mechanics — which, some suspect, have directionality and irreversibility built into them at the deepest level. According to this view, the second law comes about not because of classical probabilities but because of quantum effects such as entanglement. It arises from the ways in which quantum systems share information, and from cornerstone quantum principles that decree what is allowed to happen and what is not. In this telling, an increase in entropy is not just the most likely outcome of change. It is a logical consequence of the most fundamental resource that we know of — the quantum resource of information…
Is that most sacrosanct natural laws, second law of thermodynamics, a quantum phenomenon? “Physicists Rewrite the Fundamental Law That Leads to Disorder,” from @philipcball in @QuantaMagazine.
* “Nothing in life is certain except death, taxes and the second law of thermodynamics. All three are processes in which useful or accessible forms of some quantity, such as energy or money, are transformed into useless, inaccessible forms of the same quantity. That is not to say that these three processes don’t have fringe benefits: taxes pay for roads and schools; the second law of thermodynamics drives cars, computers and metabolism; and death, at the very least, opens up tenured faculty positions.” — Seth Lloyd
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As we get down with disorder, we might spare a thought for Francois-Marie Arouet, better known as Voltaire; he died on this date in 1778. The Father of the Age of Reason, he produced works in almost every literary form: plays, poems, novels, essays, and historical and scientific works– more than 2,000 books and pamphlets (and more than 20,000 letters). He popularized Isaac Newton’s work in France by arranging a translation of Principia Mathematica to which he added his own commentary.
A social reformer, Voltaire used satire to criticize the intolerance, religious dogma, and oligopolistic privilege of his day, perhaps nowhere more sardonically than in Candide.
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