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Posts Tagged ‘quantum theory

“There is a size at which dignity begins”*…

 

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The spectrometer for the KATRIN experiment, as it works its way through the German town of Eggenstein-Leopoldshafen in 2006 en route to the nearby Karlsruhe Institute of Technology

 

Isaac Asimov dubbed neutrinos “ghost particles.” John Updike immortalized them in verse. They’ve been the subject of several Nobel Prize citations, because these weird tiny particles just keep surprising physicists. And now we have a much better idea of the upper limit of what their rest mass could be, thanks to the first results from the Karlsruhe Tritium Neutrino experiment (KATRIN) in Germany. Leaders from the experiment announced their results last week at a scientific conference in Japan and posted a preprint to the physics arXiv.

“Knowing the mass of the neutrino will allow scientists to answer fundamental questions in cosmology, astrophysics, and particle physics, such as how the universe evolved or what physics exists beyond the Standard Model,” said Hamish Robertson, a KATRIN scientist and professor emeritus of physics at the University of Washington…

Physicists get small: “Weighing in: Physicists cut upper limit on neutrino’s mass in half.”

* Thomas Hardy, “Two on a Tower”

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As we step onto the scales, we might spare a thought for Max Karl Ernst Ludwig Planck; he died on this date in 1947.  A theoretical physicist, he is best remembered as the originator of quantum theory.  It was his discovery of energy quanta that won him the Nobel Prize in Physics in 1918.

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Written by LW

October 4, 2019 at 1:01 am

“Reality is merely an illusion, albeit a very persistent one”*…

 

Science_View-On-G2-Mirror

To look for the strange wave-like properties of quantum particles, physicists hurtle them through a long tunnel-like instrument known as an interferometer

 

Magnify a speck of dirt a thousand times, and suddenly it no longer seems to play by the same rules. Its outline, for example, won’t look well-defined most of the time and will resemble a diffuse, sprawling cloud. That’s the bizarre realm of quantum mechanics. “In some books, you’ll find they say a particle is in various places at once,” says physicist Markus Arndt of the University of Vienna in Austria. “Whether that really happens is a matter of interpretation.”

Another way of putting it: Quantum particles sometimes act like waves, spread out in space. They can slosh into each other and even back onto themselves. But if you poke at this wave-like object with certain instruments, or if the object interacts in specific ways with nearby particles, it loses its wavelike properties and starts acting like a discrete point—a particle. Physicists have observed atoms, electrons, and other minutiae transitioning between wave-like and particle-like states for decades.

But at what size do quantum effects no longer apply? How big can something be and still behave like both a particle and a wave? Physicists have struggled to answer that question because the experiments have been nearly impossible to design.

Now, Arndt and his team have circumvented those challenges and observed quantum wave-like properties in the largest objects to date—molecules composed of 2,000 atoms, the size of some proteins. The size of these molecules beats the previous record by two and a half times. To see this, they injected the molecules into a 5-meter-long tube. When the particles hit a target at the end, they didn’t just land as randomly scattered points. Instead, they formed an interference pattern, a striped pattern of dark and light stripes that suggests waves colliding and combining with each other…

One possibility physicists are exploring is that quantum mechanics might in fact apply at all scales. “You and I, while we sit and talk, do not feel quantum,” says Arndt. We seem to have distinct outlines and do not crash and combine with each other like waves in a pond. “The question is, why does the world look so normal when quantum mechanics is so weird?”…

A record-breaking experiment shows an enormous molecule is also both a particle and a wave—and that quantum effects don’t only apply at tiny scales: “Even Huge Molecules Follow the Quantum World’s Bizarre Rules.”

Read the paper published in Nature Physics by Arndt and his team here.

* Albert Einstein

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As we dwell on duality, we might spare a thought for August Ferdinand Möbius; he died on this date in 1868.  A German mathematician and theoretical astronomer, he is best remembered as a topologist, more specifically for his discovery of the Möbius strip (a two-dimensional surface with only one side… or more precisely, a non-orientable two-dimensional surface with only one side when embedded in three-dimensional Euclidean space).

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Written by LW

September 26, 2019 at 1:01 am

“I think I can safely say that nobody understands quantum mechanics”*…

 

Quantum_Darwinism_2880x1620_Lede

 

But we may be getting a little bit closer…

It’s not surprising that quantum physics has a reputation for being weird and counterintuitive. The world we’re living in sure doesn’t feel quantum mechanical. And until the 20th century, everyone assumed that the classical laws of physics devised by Isaac Newton and others — according to which objects have well-defined positions and properties at all times — would work at every scale. But Max Planck, Albert Einstein, Niels Bohr and their contemporaries discovered that down among atoms and subatomic particles, this concreteness dissolves into a soup of possibilities. An atom typically can’t be assigned a definite position, for example — we can merely calculate the probability of finding it in various places. The vexing question then becomes: How do quantum probabilities coalesce into the sharp focus of the classical world?

Physicists sometimes talk about this changeover as the “quantum-classical transition.” But in fact there’s no reason to think that the large and the small have fundamentally different rules, or that there’s a sudden switch between them. Over the past several decades, researchers have achieved a greater understanding of how quantum mechanics inevitably becomes classical mechanics through an interaction between a particle or other microscopic system and its surrounding environment.

One of the most remarkable ideas in this theoretical framework is that the definite properties of objects that we associate with classical physics — position and speed, say — are selected from a menu of quantum possibilities in a process loosely analogous to natural selection in evolution: The properties that survive are in some sense the “fittest.” As in natural selection, the survivors are those that make the most copies of themselves. This means that many independent observers can make measurements of a quantum system and agree on the outcome — a hallmark of classical behavior.

This idea, called quantum Darwinism (QD), explains a lot about why we experience the world the way we do rather than in the peculiar way it manifests at the scale of atoms and fundamental particles. Although aspects of the puzzle remain unresolved, QD helps heal the apparent rift between quantum and classical physics.

Only recently, however, has quantum Darwinism been put to the experimental test…

How do quantum possibilities give rise to objective, classical reality?  More on one possible explanation, quantum Darwinism– and on the three experiments that have have begun to vet the theory: “Quantum Darwinism, an Idea to Explain Objective Reality, Passes First Tests.”

* Richard Feynman

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As we ruminate on reality, we might recall that it was on this date in 1975 that Jimmy Hoffa disappeared from the parking lot of the Machus Red Fox restaurant in Bloomfield Hills, Michigan, a suburb of Detroit, at about 2:30 p.m.  He was never seen or heard from again.

Hoffa had served as President of the International Brotherhood of Teamsters from 1957.  Long suspected of mob ties, he was convicted of jury tampering, attempted bribery and fraud in 1964, and sentenced to 13 years in prison in 1967… from whence he continued in his union office until 1972, when he was pardoned by President Richard Nixon on the condition that he resign Teamsters office.  Out of jail, he began to plot an attempt to reverse this condition and return to power.  Before he could make much progress, he disappeared.  He was declared legally dead in 1982.  While there has never been an official explanation of Hoffa’s demise, it is widely believed that he was killed by the Mafia, which was uncomfortable with his efforts to disrupt the power structure of the Teamsters (over which they has reestablished control).

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Written by LW

July 30, 2019 at 1:01 am

“Humanize your talk, and speak to be understood”*…

 

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Personification is weird…yet entirely natural. It’s the odd practice of pretending things are people. When we personify, we apply human attributes to inanimate objects, to nature, to animals, or to abstract concepts, sometimes complete with dramatic stories about their social roles, emotions and intentions. We can observe this linguistically through features like unexpected pronoun use or certain animate verbs and adjectives that are usually only applied to people. A common example is how ships and other vessels traditionally have a feminine gender in English (even if the ship happens to be a “man-of-war“)… There’s a strange empathy in words like “she is alone” applied to an object that can’t possibly have a sense of loneliness. This isn’t the artifice of poetry, but everyday language. On the face of it, the concept of personification seems pretty crazy, the stuff of fantasy and magical thinking…

You might think, like many a respectable scientist, that it has no place in our earth logic, because not only is it not real, it is objectively false (and therefore unscientific), since inanimate objects do not have feelings or intentions (and if animals do, we can’t possibly know for sure). Yet personification is not only wildly popular in language use (even if we don’t always notice it), it’s a fascinating psychological phenomenon that reveals a lot about social cognition and how we might understand the world…

How the way we talk about the things around us both shapes and reflects our understanding of the world: “Personification Is Your Friend: The Language of Inanimate Objects.”

* Moliere

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As we muse on anthropomorphic metaphor and meaning, we might recall that today’s a relative-ly good day for it, as it was on this date in 1900 that German physicist Max Planck presented and published his study of the effect of radiation on a “black-body” substance (introducing what we’ve come to know as the Planck Postulate), and the quantum theory of modern physics– and for that matter, Twentieth Century modernity– were born.

Planck study demonstrated that in certain situations energy exhibits the characteristics of physical matter– something unthinkable at the time– and suggested that energy exists in discrete packets, which he called “quanta”… thus laying the foundation on which he, Einstein, Bohr, Schrodinger, Dirac, and others built our modern understanding.

220px-Max_Planck_1933Max Planck

 

Written by LW

December 14, 2018 at 1:01 am

“As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality.”*…

 

quantum computing

Quantum computing is all the rage. It seems like hardly a day goes by without some news outlet describing the extraordinary things this technology promises. Most commentators forget, or just gloss over, the fact that people have been working on quantum computing for decades—and without any practical results to show for it.

We’ve been told that quantum computers could “provide breakthroughs in many disciplines, including materials and drug discovery, the optimization of complex manmade systems, and artificial intelligence.” We’ve been assured that quantum computers will “forever alter our economic, industrial, academic, and societal landscape.” We’ve even been told that “the encryption that protects the world’s most sensitive data may soon be broken” by quantum computers. It has gotten to the point where many researchers in various fields of physics feel obliged to justify whatever work they are doing by claiming that it has some relevance to quantum computing.

Meanwhile, government research agencies, academic departments (many of them funded by government agencies), and corporate laboratories are spending billions of dollars a year developing quantum computers. On Wall Street, Morgan Stanley and other financial giants expect quantum computing to mature soon and are keen to figure out how this technology can help them.

It’s become something of a self-perpetuating arms race, with many organizations seemingly staying in the race if only to avoid being left behind. Some of the world’s top technical talent, at places like Google, IBM, and Microsoft, are working hard, and with lavish resources in state-of-the-art laboratories, to realize their vision of a quantum-computing future.

In light of all this, it’s natural to wonder: When will useful quantum computers be constructed? The most optimistic experts estimate it will take 5 to 10 years. More cautious ones predict 20 to 30 years. (Similar predictions have been voiced, by the way, for the last 20 years.) I belong to a tiny minority that answers, “Not in the foreseeable future.” Having spent decades conducting research in quantum and condensed-matter physics, I’ve developed my very pessimistic view. It’s based on an understanding of the gargantuan technical challenges that would have to be overcome to ever make quantum computing work…

Michel Dyakonov makes “The Case Against Quantum Computing.”

* Albert Einstein

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As we feel the need for speed, we might recall that it was on this date in 1942 that a team of scientists led by Enrico Fermi, working inside an enormous tent on a squash court under the stands of the University of Chicago’s Stagg Field, achieved the first controlled nuclear fission chain reaction… laying the foundation for the atomic bomb and later, nuclear power generation.

“…the Italian Navigator has just landed in the New World…”
– Coded telephone message confirming first self-sustaining nuclear chain reaction, December 2, 1942.

Illustration depicting the scene on Dec. 2, 1942 (Photo copyright of Chicago Historical Society)

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Indeed, exactly 15 years later, on this date in 1957, the world’s first full-scale atomic electric power plant devoted exclusively to peacetime uses, the Shippingport Atomic Power Station, reached criticality; the first power was produced 16 days later, after engineers integrated the generator into the distribution grid of Duquesne Light Company.

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Written by LW

December 2, 2018 at 1:01 am

“A measurement is not an absolute thing, but only relates one entity to another”*…

 

kilogram

 

Until now, [the mass of the kilogram] has been defined by the granddaddy of all kilos: a golf ball-sized metal cylinder locked in a vault in France [a replica of which is pictured above]. For more than a century, it has been the one true kilogram upon which all others were based…

Made of a corrosion-resistant alloy of 90 percent platinum and 10 percent iridium , the international prototype kilo has rarely seen the light of day. Yet its role has been crucial, as the foundation for the globally accepted system for measuring mass upon which things like international trade depend.

Three different keys, kept in separate locations, are required to unlock the vault where the Grand K and six official copies — collectively known as ‘‘the heir and the spares’’ — are entombed together under glass bell-jars at the International Bureau of Weights and Measures, in Sevres on the western outskirts of Paris.

Founded by 17 nations in 1875 and known by its French initials, the BIPM is the guardian of the seven main units humanity uses to measure its world : the meter for length, the kilogram for mass, the second for time, the ampere for electric current, the kelvin for temperature, the mole for the amount of a substance and the candela for luminous intensity.

Of the seven, the kilo is the last still based on a physical artifact, the Grand K. The meter, for example, used to be a meter-long metal bar but is now defined as the length that light travels in a vacuum in 1/299,792,458th of a second…

The metal kilo is being replaced by a definition based on Planck’s constant, which is part of one of the most celebrated equations in physics but also devilishly difficult to explain . Suffice to say that the update should, in time, spare nations the need to occasionally send their kilos back to Sevres for calibration against the Grand K. Scientists instead should be able to accurately calculate an exact kilo, without having to measure one precious lump of metal against another…

More of this weighty story at “The kilogram is changing. Weight, what?

* H.T. Pledge, Science since 1500

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As we muse on measurement, we might send well-calibrated birthday greetings to August Kundt; he was born on this date in 1839.  An astronomer-turned-physicist, he developed a method to measure the velocity of sound in gases and solids using a closed glass tube (now known as a Kundt’s Tube).

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We might also spare a thought for another physicist, Niels Bohr; he died on this date in 1962.  A Danish physicist and philosopher, Bohr was the first to apply quantum theory to the problem of atomic and molecular structure, creating the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete, and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level (or orbit) to another– a model the underlying principles of which remain valid.  And he developed the principle of complementarity: that items could be separately analyzed in terms of contradictory properties, e.g., particles behaving as a wave or a stream. His foundational contributions to understanding atomic structure and quantum theory won him the Nobel Prize in Physics in 1922.

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“Doubtless we cannot see that other higher Spaceland now, because we have no eye in our stomachs”*…

 

An ” Amplituhedron“, an illustration of multi-dimensional spacetime

Our architecture, our education and our dictionaries tell us that space is three-dimensional. The OED defines it as ‘a continuous area or expanse which is free, available or unoccupied … The dimensions of height, depth and width, within which all things exist and move.’ In the 18th century, Immanuel Kant argued that three-dimensional Euclidean space is an a priori necessity and, saturated as we are now in computer-generated imagery and video games, we are constantly subjected to representations of a seemingly axiomatic Cartesian grid. From the perspective of the 21st century, this seems almost self-evident.

Yet the notion that we inhabit a space with any mathematical structure is a radical innovation of Western culture, necessitating an overthrow of long-held beliefs about the nature of reality. Although the birth of modern science is often discussed as a transition to a mechanistic account of nature, arguably more important – and certainly more enduring – is the transformation it entrained in our conception of space as a geometrical construct.

Over the past century, the quest to describe the geometry of space has become a major project in theoretical physics, with experts from Albert Einstein onwards attempting to explain all the fundamental forces of nature as byproducts of the shape of space itself. While on the local level we are trained to think of space as having three dimensions, general relativity paints a picture of a four-dimensional universe, and string theory says it has 10 dimensions – or 11 if you take an extended version known as M-Theory. There are variations of the theory in 26 dimensions, and recently pure mathematicians have been electrified by a version describing spaces of 24 dimensions. But what are these ‘dimensions’? And what does it mean to talk about a 10-dimensional space of being?…

Experience says we live in three dimensions; relativity says four; string theory says it’s 10– or more… What are “dimensions” and how do they affect reality? Margaret Wertheim offers a guide: “Radical dimensions.”

* Edwin A. Abbott, Flatland: A Romance of Many Dimensions

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As we tax our senses, we might spare a thought for Robert Jemison Van de Graaff; he died on this date in 1967.  A physicist and engineer, he is best remembered for his creation of the Van de Graaff Generator, an electrostatic generator that creates very high electric potentials– very high voltage direct current (DC) electricity (up to 5 megavolts) at low current levels.  A tabletop version can produce on the order of 100,000 volts and can store enough energy to produce a visible spark. Such small Van de Graaff machines are used in physics education to teach electrostatics; larger ones are displayed in some science museums.

Boy touching Van de Graaff generator at The Magic House, St. Louis Children’s Museum. Charged with electricity, his hair strands repel each other and stand out from his head.

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Written by LW

January 16, 2018 at 1:01 am

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