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Posts Tagged ‘quantum mechanics

“Aside from velcro, time is the most mysterious substance in the universe”*…

 

Time

Detail from Salvador Dali’s Persistence of Memory

 

In normal life, you open the car door before getting into the car. Operation A happens before operation B. That’s the causal order of things. But a new quantum switch weirdly enables two operations to happen simultaneously. From Science News:

The device, known as a quantum switch, works by putting particles of light through a series of two operations — labeled A and B — that alter the shape of the light. These photons can travel along two separate paths to A and B. Along one path, A happens before B, and on the other, B happens before A.

Which path the photon takes is determined by its polarization, the direction in which its electromagnetic waves wiggle — up and down or side to side. Photons that have horizontal polarization experience operation A first, and those with vertical polarization experience B first.

But, thanks to the counterintuitive quantum property of superposition, the photon can be both horizontally and vertically polarized at once. In that case, the light experiences both A before B, and B before A, Romero and colleagues report.

While this is deeply weird and amazing, it unfortunately doesn’t occur at the human scale but rather in the quantum realm where measurements are in the nanometers. Still, quantum switches do have clear applications in future communications and computation systems.

Indefinite Causal Order in a Quantum Switch” (Physical Review Letters)

From the ever-illuminating David Pescovitz at Boing Boing: “Weird time-jumbling quantum device defies ‘before’ and ‘after’.”

* Dave Barry

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As we check our watches, we might send timely birthday greetings to Louis Essen; he was born on this date in 1908.  A physicist, he drew on his World War II work on radar to develop the first generally-accepted scientific measurement of the speed of light (one that has held up well as measurement techniques have advanced.).

But Essen is probably better remembered as the father of the atomic clock: in 1955, in collaboration with Jack Parry, he developed the first practical atomic clock by integrating the caesium atomic standard with conventional quartz crystal oscillators to allow calibration of existing time-keeping.

Atomic_Clock-Louis_Essen

Louis Essen (right) and Jack Parry (left) standing next to the world’s first caesium-133 atomic clock

 

Written by LW

September 6, 2018 at 1:01 am

“The true sign of intelligence is not knowledge but imagination”*…

 

Perhaps Arthur C. Clarke was being uncharacteristically unambitious. He once pointed out that any sufficiently advanced technology is going to be indistinguishable from magic. If you dropped in on a bunch of Paleolithic farmers with your iPhone and a pair of sneakers, you’d undoubtedly seem pretty magical. But the contrast is only middling: The farmers would still recognize you as basically like them, and before long they’d be taking selfies. But what if life has moved so far on that it doesn’t just appear magical, but appears like physics?

After all, if the cosmos holds other life, and if some of that life has evolved beyond our own waypoints of complexity and technology, we should be considering some very extreme possibilities. Today’s futurists and believers in a machine “singularity” predict that life and its technological baggage might end up so beyond our ken that we wouldn’t even realize we were staring at it. That’s quite a claim, yet it would neatly explain why we have yet to see advanced intelligence in the cosmos around us, despite the sheer number of planets it could have arisen on—the so-called Fermi Paradox…

Caleb Scharf on the possibility that alien life could be so advanced it is indistinguishable from physics: “Is Physical Law an Alien Intelligence?

For a very different perspective (albeit, one seemingly rooted in a more narrowly-defined understanding of “life”), see “A Key Evolutionary Step May Mean Intelligent Alien Life Doesn’t Exist in the Universe.”

* Albert Einstein

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As we think through the thought experiment, we might send uncertain birthday greetings to Werner Karl Heisenberg; he was born on this date in 1901.  A theoretical physicist, he made 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.

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“There is nothing more wonderful than a list, instrument of wondrous hypotyposis”*…

 

Da Vinci would carry around a notebook, where he would write and draw anything that moved him. “It is useful,” Leonardo once wrote, to “constantly observe, note, and consider.” Buried in one of these books, dating back to around the 1490s, is a to-do list. And what a to-do list…

Check it out (if not off) at “Leonardo Da Vinci’s To Do List (Circa 1490) Is Much Cooler Than Yours.”

* Umberto Eco, The Name of the Rose

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As we prioritize prioritization, we might spare a thought for Erwin Rudolf Josef Alexander Schrödinger; he died on this date in 1961.  A physicist best remembered in his field for his contributions to the development of quantum mechanics (e.g., the Schrödinger equation), and more generally for his “Schrödinger’s cat thought experiment– a critique of the Copenhagen interpretation of quantum mechanics– he also wrote on philosophy and theoretical biology.  Indeed, both James Watson, and independently, Francis Crick, co-discoverers of the structure of DNA, credited Schrödinger’s What is Life? (1944), with its theoretical description of how the storage of genetic information might work, as an inspiration.

It seems plain and self-evident, yet it needs to be said: the isolated knowledge obtained by a group of specialists in a narrow field has in itself no value whatsoever, but only in its synthesis with all the rest of knowledge and only inasmuch as it really contributes in this synthesis toward answering the demand, “Who are we?”

– from Science and Humanism, 1951

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Written by LW

January 4, 2017 at 1:01 am

“Nothing puzzles me more than time and space; and yet nothing troubles me less”…

 

Time crystals– crystals that break both spacial and temporal symmetry– were first predicted by Nobel laureate Frank Wilczek in 2012… and were widely deemed amusing, but impossible (e.g., here).  Now researchers have created time crystals for the first time and say they could one day be used as quantum memories… and might help reconcile Quantum Mechanics with the Theory of Relativity.

Bend your mind at “Physicists Create World’s First Time Crystal,” also here and here (source of the photo above).

* Charles Lamb

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As we ponder Einstein’s insistence that time is an illusion, we might send well-structured birthday greetings to Pierre-Gilles de Gennes; he was born on this date in 1932.  A French physicist, he was awarded the 1991 Nobel Prize for Physics for “discovering that methods developed for studying order phenomena in simple systems can be generalized to more complex forms of matter, in particular to liquid crystals and polymers.”  He described mathematically how, for example, magnetic dipoles, long molecules or molecule chains can under certain conditions form ordered states, and what happens when they pass from an ordered to a disordered state.  Such changes of order occur when, for example, a heated magnet changes from a state in which all the small atomic magnets are lined up in parallel to a disordered state in which the magnets are randomly oriented.  Later, he was concerned with the physical chemistry of adhesion.

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Written by LW

October 24, 2016 at 1:01 am

Playing at life…

 

For years both scientists and science fiction writers have suggested that a sufficiently advanced civilisation could– and thus would– create a simulated universe.  And since simulations beget simulations (within simulations, within simulations, etc., etc.), there would ultimately be many more simulated universes than real ones…  meaning that it would be more likely than not that any one universe– say, ours– is artificial.

Silas Beane, working with a team at the University of Bonn says he have evidence this may be true.  The Physics arXiv Blog at Technology Review explains:

 

First, some background. The problem with all simulations is that the laws of physics, which appear continuous, have to be superimposed onto a discrete three dimensional lattice which advances in steps of time.

The question that Beane and co ask is whether the lattice spacing imposes any kind of limitation on the physical processes we see in the universe. They examine, in particular, high energy processes, which probe smaller regions of space as they get more energetic

What they find is interesting. They say that the lattice spacing imposes a fundamental limit on the energy that particles can have. That’s because nothing can exist that is smaller than the lattice itself.

So if our cosmos is merely a simulation, there ought to be a cut off in the spectrum of high energy particles.

It turns out there is exactly this kind of cut off in the energy of cosmic ray particles,  a limit known as the Greisen–Zatsepin–Kuzmin or GZK cut off.

This cut-off has been well studied and comes about because high energy particles interact with the cosmic microwave background and so lose energy as they travel  long distances.

But Beane and co calculate that the lattice spacing imposes some additional features on the spectrum. “The most striking feature…is that the angular distribution of the highest energy components would exhibit cubic symmetry in the rest frame of the lattice, deviating significantly from isotropy,” they say.

In other words, the cosmic rays would travel preferentially along the axes of the lattice, so we wouldn’t see them equally in all directions.

That’s a measurement we could do now with current technology. Finding the effect would be equivalent to being able to to ‘see’ the orientation of lattice on which our universe is simulated…

Read the whole mind-blowing story (including some comforting caveats) at “The Measurement That Would Reveal The Universe As A Computer Simulation” (and find Beane’s paper here).

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As we wonder if there’s a “reset” button, we might spare a thought for the extraordinary Erwin Rudolf Josef Alexander Schrödinger; he died on this date in 1961.  A physicist best remembered in his field for his contributions to the development of quantum mechanics (e.g., the Schrödinger equation), and more generally for his “Schrödinger’s cat thought experiment– a critique of the Copenhagen interpretation of quantum mechanics– he also wrote on philosophy and theoretical biology.  Indeed, both James Watson, and independently, Francis Crick, co-discoverers of the structure of DNA, credited Schrödinger’s What is Life? (1944), with its theoretical description of how the storage of genetic information might work, as an inspiration.

It seems plain and self-evident, yet it needs to be said: the isolated knowledge obtained by a group of specialists in a narrow field has in itself no value whatsoever, but only in its synthesis with all the rest of knowledge and only inasmuch as it really contributes in this synthesis toward answering the demand, “Who are we?”

– from Science and Humanism, 1951

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Written by LW

January 4, 2013 at 1:01 am

News that isn’t…

From corrections…

… to photos…

…to typos…

… readers will find the backstories to these gaffes and myriad others at Poynter’s “The best (and worst) media errors and corrections of 2012.”

Special Bonus:  Jim Romenesko’s Headline of the Year: “Maneater: Hall Bitten by Oates.”

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As we fixate on fact-checking, we might recall that this is the birthday of quantum physics: it was on this date in 1900 that Max Planck published his study of the effect of radiation on a “blackbody” substance, demonstrating that in certain situations energy exhibits the characteristics of physical matter– something unthinkable at the time– and suggesting 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 of physics.

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Written by LW

December 14, 2012 at 1:01 am

To See What Condition My Condition Was In…

Could Quantum Mechanics be wrong?

The philosophical status of the wavefunction — the entity that determines the probability of different outcomes of measurements on quantum-mechanical particles — would seem to be an unlikely subject for emotional debate. Yet online discussion of a paper claiming to show mathematically that the wavefunction is real has ranged from ardently star-struck to downright vitriolic since the article was first released as a preprint in November 2011.

The paper, thought by some to be one of the most important in quantum foundations in decades, was finally published last week in Nature Physics (M. F. Pusey, J. Barrett & T. Rudolph Nature Phys. http://dx.doi.org/10.1038/nphys2309; 2012), enabling the authors, who had been concerned about violating the journal’s embargo, to speak about it publicly for the first time. They say that the mathematics leaves no doubt that the wavefunction is not just a statistical tool, but rather, a real, objective state of a quantum system…

The authors have some heavyweights in their corner: their view was once shared by Austrian physicist and quantum-mechanics pioneer Erwin Schrödinger, who proposed in his famous thought experiment that a quantum-mechanical cat could be dead and alive at the same time. But other physicists have favoured an opposing view, one held by Albert Einstein: that the wavefunction reflects the partial knowledge an experimenter has about a system. In this interpretation, the cat is either dead or alive, but the experimenter does not know which. This ‘epistemic’ interpretation, many physicists and philosophers argue, better explains the phenomenon of wavefunction collapse, in which a quantum state is fundamentally changed by measuring it…

Read the full story in Nature.

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As we listen for the tell-tale purr, we might spare a thought for Gerbert d’Aurillac (who became Pope Sylvester II); he died on this date in 1003.  Gerbert/Sylvester was never canonized; indeed, in his day, he dogged with rumors that he was a sorcerer in league with the devil… which appear to have been the work of reactionary forces resisting both Sylvester’s attempts to rid the Church of corruption (especially simony, the sale of sacraments and indulgences) and his attempts to popularize mathematics, astronomy and mechanics for lay audiences.  Inspired by translations of Arabic texts, he built clocks, invented the hydraulic organ, crafted astronomical instruments, and renewed interest in the abacus for use in mathematical calculations (in the process of which, he seems to have introduced Arabic numerals [except zero]).  It’s not a stretch to suggest that Gerbert/Sylvester began Europe’s long march out of the Dark Ages.

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