Category Archives: Quantum Physics

Quantum computing could be the solution to the challenges that are faced by quantum physicists. It has the power to change our fundamental understanding of reality, and it could soon become a reality.

Quantum computing is an area of research in which engineers, scientists, and technologists are trying to build a computer where information is represented at the quantum level.

Quantum computers would be able to solve problems that are not possible with classical computers or solve them much more quickly. Today's silicon-based computer chips use binary digits (bits) with values of either 0 or 1 for storing information. These bits exist in two states at any given time and can't represent both 0 and 1 simultaneously like qubits which can represent all values at once thanks to the quantum mechanics principle called superpositioning.

Classical Computers VS Quantum ComputersTo understand how quantum computing works, it's important to know the difference between the old (classical) way of computing and the new (quantum) way.

On classical computers, information is encoded into binary digits called "bits." These bits can be in one of two states: 0 or 1. A qubit also has two possible states - 0, 1, or both at once (superposition). This means that it can encode much more information than a binary digit. The physical world behaves according to quantum mechanics. So theoretically, if we want to simulate physical phenomena on a computer, we should use quantum mechanical principles as well

Now that we have made the switching and memory units of computers, known as transistors, almost as small as an atom, we need to find an entirely new way of thinking about and building computers. Quantum computers are not intended to replace classical computers, they are expected to be a different tool we will use to solve complex problems that are beyond the capabilities of a classical computer. A problem that requires more power and time than today's computers can accommodate is called an intractable problem. These are the problems that quantum computers are predicted to solve.

When you enter the world of atomic and subatomic particles, things begin to behave in unexpected ways. It's this ability that quantum computers take advantage of. By entering into this quantum area of computing where the traditional laws of physics no longer apply, we will be able to create processors that are significantly faster than the ones we use today. Sounds fantastic, but the challenge is that quantum computing is also incredibly complex.

That's precisely why the computer industry is racing to make quantum computers work on a commercial scale.

Quantum computers are different from traditional computers because they use quantum bits (qubits) instead of binary bits. One qubit can be in two states at the same time, which solves many problems that current computers don't. Moreover, quantum computing can solve highly complex problems by using "parallelism" to process many calculations at the same time. The downside to this technology is that it needs an enormous amount of energy for operations to work properly. For instance, IBM has said that qubits need about 100 milliwatts of power per operation whereas regular processors need about 10 kilowatts

The Quantum Revolution

The practical uses of quantum computers are still being researched and tested. In the future, it is possible that quantum computers will be able to solve problems that have been impossible to solve before. For example, they have the potential to be used for modelling molecules or predicting how a molecule will behave under different conditions.

We should also remember that a quantum computer is not faster than a regular computer - it's just more powerful. That means that "running" a program on a quantum computer will take just as long as on a regular computer - but with much better results because of their increased power.Quantum computers will allow for the storage and processing of data in ways that we cannot even comprehend today. They also offer more complex calculations than traditional computers and therefore can easily solve problems that would take years to solve on a traditional computer.

Some experts believe that they could be used to calculate complex formulas with no time limit, which will make them an invaluable tool in medical science, AI technologies, aeronautical engineering and so on. So far, quantum computing has been used to solve optimization problems, which are too complex for traditional computer models. It's also been used to study protein folding and drug interactions within the body.

Quantum computers are powerful computers that work on the principles of quantum mechanics. They use qubits, not bits to represent data and they can access potentially more than two values at the same time. Quantum computers will be able to break all of the encoding and encryption we have today. Quantum computing is changing the world of cybersecurity. Quantum computers are capable of running sophisticated simulations in parallel, making them much faster than classical computers. The ability to run simulations in parallel means that quantum computers can quickly find solutions to difficult problems. Quantum computers will disrupt many industries like finance, healthcare, and education.

While it's still unclear how big of an impact quantum computing will have on marketing in the future, there are already some significant uses happening now. One example is in ad targeting where companies can analyze customer behaviour with astounding precision by processing large amounts.

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The Future of Quantum Computing - The Business Standard

Albert Einsteins handwritten notes on the theory of relativity fetched a record 11.6m (9.7m) at an auction in Paris on Tuesday.

The manuscript had been valued at about a quarter of the final sum, which is by far the highest ever paid for anything written by the genius scientist.

It contains preparatory work for the physicists signature achievement, the theory of general relativity, which he published in 1915.

Calling the notes without a doubt the most valuable Einstein manuscript ever to come to auction, Christies which handled the sale on behalf of the Aguttes auction house had estimated prior to the auction that it would fetch between 2m and 3m.

Previous records for Einsteins works were $2.8m for the so-called God letter in 2018, and $1.56m in 2017 for a letter about the secret to happiness.

The 54-page document was handwritten in 1913 and 1914 in Zurich, Switzerland, by Einstein and his colleague and confidant Michele Besso, a Swiss engineer.

Christies said it was thanks to Besso that the manuscript was preserved for posterity. This was almost like a miracle, it said, since Einstein would have been unlikely to hold on to what he considered to be a simple working document.

Today the paper offered a fascinating plunge into the mind of the 20th centurys greatest scientist, Christies said. It discusses his theory of general relativity, building on his theory of special relativity from 1905 that was encapsulated in the equation E=mc2.

Einstein died in 1955 aged 76, lauded as one of the greatest theoretical physicists of all time. His theories of relativity revolutionised his field by introducing new ways of looking at the movement of objects in space and time.

In 1913 Besso and Einstein attacked one of the problems that had been troubling the scientific community for decades: the anomaly of the planet Mercurys orbit, Christies said.

This initial manuscript contains a certain number of unnoticed errors, it added. Once Einstein spotted them, he let the paper drop, and it was taken away by Besso.

Scientific documents by Einstein in this period, and before 1919 generally, are extremely rare, Christies said. Being one of only two working manuscripts documenting the genesis of the theory of general relativity that we know about, it is an extraordinary witness to Einsteins work.

Einstein also made major contributions to quantum mechanics theory and won the Nobel physics prize in 1921. He became a pop culture icon thanks to his dry witticisms and trademark unruly hair, moustache and bushy eyebrows.

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Einsteins notes on theory of relativity fetch record 11.6m at auction - The Guardian

How is it that a chef can control their knife to fillet a fish or peel a grape and can wield a cleaver just as efficiently as a paring knife? Even those of us less proficient in the kitchen learn to skilfully handle an astonishing number of different objects throughout our lives, from shoelaces to tennis rackets.

This ability to continuously acquire new skills, without forgetting or degrading old ones, comes naturally to humans but is a major challenge even for todays most advanced artificial intelligence systems.

Now, scientists from the University of Cambridge and Columbia University have developed and experimentally verified a new mathematical theory that explains how the human brain achieves this feat, they write in a press release. Called the COntextual INference (COIN) model, it suggests that identifying the current context is key to learning how to move our bodies.

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The model describes a mechanism in the brain that is constantly trying to figure out the current context. The theory suggests that these continuously changing beliefs about context determine how to use existing memories and whether to form new ones. Theresultsare reported in the journalNature.

Imagine playing tennis with a different racket than usual or switching from tennis to squash, said co-senior author Dr Daniel Wolpert from Columbia University. Our theory explores how your brain adjusts to these situations and whether to treat them as distinct contexts.

According to the COIN model, the brain maintains a repertoire of motor memories, each associated with the context in which it was created, such as playing squash versus tennis. Even for a single swing of the racket, the brain can draw upon many memories, each in proportion to how much the brain believes it is currently in the context in which that memory was created.

This goes against the traditional view that only one memory is used at a time. To improve performance on the next swing, the brain also updates all memories, once again depending on its belief about the current context. When the context of the movement is judged to be new (the first time we play squash after years of tennis, for example), the brain automatically creates a new memory for that context. This ensures that we do not overwrite previously established memories, such as the memory for playing tennis.

This research may lead to better physical therapy strategies to help people with injuries use their bodies again. Often the improvements seen in the setting of a physical therapists office do not transfer to improvements in the real world.

With a better understanding of how context affects motor learning, you can think about how to nudge the brain to generalise what it learns to contexts outside of the physical therapy session, said first author Dr James Heald. A better understanding of the basic mechanisms that underlie the context dependence of memory and learning could have therapeutic consequences in this area.

What I find exciting is that the principles of the COIN model may also generalise to many other forms of learning and memory, not just memories underlying our movement, said co-senior author Professor Mt Lengyel from Cambridges Department of Engineering. For example, the spontaneous recurrence of seemingly forgotten memories, often triggered by a change in our surroundings, has been observed both in motor learning and in post-traumatic stress disorder.

Practice with a tennis racket, and the brain forms motor memories of how you moved your arm and the rest of your body that improve your serve over time. But learning isnt as simple as just making better memories to make movements more precise, the researchers said. Otherwise, a tennis players serves might improve to the point at which they never hit a ball out of bounds. The real world and our nervous systems are complex, and the brain has to deal with a lot of variability.

How does the brain distinguish this noise these random fluctuations from new situations? And how does it understand that a slightly lighter tennis racket can still be operated using previous tennis racket memories? But that a table tennis paddle is an entirely different kind of object that requires starting from scratch?

The answer, according to the COIN model, may be Bayesian inference, a mathematical technique used to deal with uncertainty. This method statistically weighs new evidence in light of prior experience in order to update ones beliefs in a changeable world. In the COIN model, a context is a simplifying assumption that, in a given set of circumstances, certain actions are more likely to lead to some consequences than others. The new theorys acceptance of the role that uncertainty plays in motor learning is similar to how quantum physics views the universe in terms of probabilities instead of certainties, the scientists noted.

The researchers put the COIN model to the test on data from previous experiments, as well as new experiments, in which volunteers interacted with a robotic handle. Participants learned to manipulate the handle to reach a target while the handle pushed back in different ways.

Volunteers who spent time learning to operate the handle as it pushed to the left, for instance, had more trouble operating the handle when it changed behaviour and pushed to the right, as compared to volunteers who started with a handle pushing to the right. The COIN model explained this effect, called anterograde interference.

The longer you learn one task, the less likely you are to move into a new context with the second task, said Wolpert. Youre still forming a motor memory of the second task, but youre not using it yet because your brain is still stuck back in the first context.

The model also predicted that a learned skill can re-emerge even after subsequent training seems to have erased it. Called spontaneous recovery, this re-emergence is seen in many other forms of learning besides motor learning. For example, spontaneous recovery has been linked with challenges in treating post-traumatic stress disorder, where contexts can trigger traumatic memories to spontaneously recur.

Scientists usually explain spontaneous recovery by invoking two different learning mechanisms. In one, memories learned quickly are forgotten quickly, and in the other, memories learned slowly are forgotten slowly, and can thus reappear. In contrast, the COIN model suggests there is just one mechanism for learning instead of two separate ones, and that memories that apparently vanished may be ready to pop back with the right trigger: the belief that the context has re-emerged. The researchers confirmed this in their lab with new experiments.

Interesting? Read our article Your own skin as running coach here.

Link:

For the brain, context is key to new theory of movement and memory - Innovation Origins

It is the central question in quantum mechanics, and no one knows the answer: What really happens in a superpositionthe peculiar circumstance in which particles seem to be in two or more places or states at once? In 2018 a team of researchers in Israel and Japan proposed an experiment that could finally let us say something for sure about the nature of this puzzling phenomenon.

Their experiment was designed to enable scientists to sneak a glance at where an objectin this case a particle of light, called a photonactually resides when it is placed in a superposition. And the researchers predict the answer will be even stranger and more shocking than two places at once.

The classic example of a superposition involves firing photons at two parallel slits in a barrier. One fundamental aspect of quantum mechanics is that tiny particles can behave like waves, so that those passing through one slit interfere with those going through the other, their wavy ripples either boosting or canceling one another to create a characteristic pattern on a detector screen. The odd thing, though, is this interference occurs even if only one particle is fired at a time. The particle seems somehow to pass through both slits at once, interfering with itself. Thats a superposition.

And it gets weirder: Measuring which slit such a particle goes through will invariably indicate it only goes through onebut then the wavelike interference (the quantumness, if you will) vanishes. The very act of measurement seems to collapse the superposition. We know something fishy is going on in a superposition, says physicist Avshalom Elitzur of the Israeli Institute for Advanced Research. But youre not allowed to measure it. This is what makes quantum mechanics so diabolical.

For decades researchers have stalled at this apparent impasse. They cannot say exactly what a superposition is without looking at it, but if they try to look at it, it disappears. One potential solutiondeveloped by Elitzurs former mentor, Israeli physicist Yakir Aharonov, now at Chapman University, and his collaboratorssuggests a way to deduce something about quantum particles before measuring them. Aharonovs approach is called the two-state-vector formalism (TSVF) of quantum mechanics and postulates quantum events are in some sense determined by quantum states not just in the pastbut also in the future. That is, the TSVF assumes quantum mechanics works the same way both forward and backward in time. From this perspective, causes can seem to propagate backward in time, occurring after their effects: a phenomenon called retrocausation.

But one neednt take this strange notion literally. Rather in the TSVF, one can gain retrospective knowledge of what happened in a quantum system by selecting the outcome: Instead of simply measuring where a particle ends up, a researcher chooses a particular location in which to look for it. This is called postselection, and it supplies more information than any unconditional peek at outcomes ever could. This is because the particles state at any instant is being evaluated retrospectively in light of its entire history, up to and including measurement. The oddness comes in because it looks as if the researchersimply by choosing to look for a particular outcomethen causes that outcome to happen. But this is a bit like concluding that if you turn on your television when your favorite program is scheduled, your action causes that program to be broadcast at that very moment. Its generally accepted that the TSVF is mathematically equivalent to standard quantum mechanics, says David Wallace, a philosopher of science at the University of Southern California, who specializes in interpretations of quantum mechanics. But it does lead to seeing certain things one wouldnt otherwise have seen.

Take, for instance, a version of the double-slit experiment devised by Aharonov and his co-worker Lev Vaidman of Tel Aviv University in 2003, which they interpreted with the TSVF. The pair described (but did not build) an optical system in which a single photon acts as a shutter that closes a slit by causing another probe photon approaching the slit to be reflected back the way it came. By applying postselection to the measurements of the probe photon, Aharonov and Vaidman showed, one could discern a shutter photon in a superposition closing both (or indeed arbitrarily many) slits simultaneously. In other words, this thought experiment would in theory allow one to say with confidence the shutter photon is both here and there at once. Although this situation seems paradoxical from our everyday experience, it is one well-studied aspect of the so-called nonlocal properties of quantum particles, where the whole notion of a well-defined location in space dissolves.

In 2016 physicists Ryo Okamoto and Shigeki Takeuchi of Kyoto University verified Aharonov and Vaidmans predictions experimentally using a light-carrying circuit in which the shutter photon is created using a quantum router, a device that lets one photon control the route taken by another. This was a pioneering experiment that allowed one to infer the simultaneous position of a particle in two places, says Elitzurs colleague Eliahu Cohen of the University of Ottawa in Ontario.

Now Elitzur and Cohen have teamed up with Okamoto and Takeuchi to concoct an even more mind-boggling experiment. They believe it will enable researchers to say with certainty something about the location of a particle in a superposition at a series of different points in timebefore any actual measurement has been made.

This time the probe photons route would be split into three by partial mirrors. Along each of those paths it may interact with a shutter photon in a superposition. These interactions can be considered to take place within boxes labeled A, B and C, one of which is situated along each of the photons three possible routes. By looking at the self-interference of the probe photon, one can retrospectively conclude with certainty the shutter particle was in a given box at a specific time.

The experiment is designed so the probe photon can only show interference if it interacted with the shutter photon in a particular sequence of places and times: namely, if the shutter photon was in both boxes A and C at some time (t1), then at a later time (t2) only in C, and at a still later time (t3) in both B and C. So interference in the probe photon would be a definitive sign the shutter photon made this bizarre, logic-defying sequence of disjointed appearances among the boxes at different timesan idea Elitzur, Cohen and Aharonov proposed as a possibility in 2017 for a single particle spread across three boxes. I like the way this paper frames questions about what is happening in terms of entire histories rather than instantaneous states, says physicist Ken Wharton of San Jos State University, who is not involved in the new project. Talking about states is an old pervasive bias, whereas full histories are generally far more rich and interesting.

That richness, Elitzur and his colleagues argue, is what the TSVF gives access to. The apparent vanishing of particles in one place at one timeand their reappearance in other times and placessuggests an extraordinary vision of the underlying processes involved in the nonlocal existence of quantum particles. Through the lens of the TSVF, Elitzur says, this flickering, ever changing existence can be understood as a series of events in which a particles presence in one place is canceled by its own counterparticle in the same location. He compares this with the idea introduced by British physicist Paul Dirac in the 1920s, who argued that particles possess antiparticles, and if brought together, a particle and antiparticle can annihilate each other. At first this notion seemed just a manner of speaking but soon led to the discovery of antimatter. The disappearance of quantum particles is not annihilation in this same sense, but it is somewhat analogous: these putative counterparticles, Elitzur posits, should possess negative energy and negative mass, allowing them to cancel their counterparts.

So although the traditional two places at once view of superposition might seem odd enough, its possible a superposition is a collection of states that are even crazier, Elitzur says. Quantum mechanics just tells you about their average. Postselection then allows one to isolate and inspect just some of those states at greater resolution, he suggests. Such an interpretation of quantum behavior would be, he says, revolutionarybecause it would entail a hitherto unguessed menagerie of real (but very odd) states underlying counterintuitive quantum phenomena.

Okamoto and his colleagues in Kyoto have now carried out the proposed experiment using photons, but they are still analyzing the results. All the same, Cohen says, the preliminary results accord well with the theory. He says the Japanese researchers are now making improvements to the setup to shrink the error bars.

For now some outside observers are not exactly waiting with bated breath. The experiment is bound to work, Wharton saysbut he adds it wont convince anyone of anything, since the results are predicted by standard quantum mechanics. In other words, there would be no compelling reason to interpret the outcome in terms of the TSVF rather than one of the many other ways that researchers interpret quantum behavior.

Elitzur agrees their experiment could have been conceived using the conventional view of quantum mechanics that prevailed decades agobut it never was. Isnt that a good indication of the soundness of the TSVF? he asks. And if someone thinks they can formulate a different picture of what is really going on in this experiment using standard quantum mechanics, he adds, Well, let them go ahead!

He is confident that the work heralds nothing short of a revolution within quantum mechanics. Now that measurement methods have become precise enough, he says, you can be sure that notions like retrocausation are going to become part and parcel of quantum reality.

Originally posted here:

Quantum Physics May Be Even Spookier Than You Think ...

Quantum theory is peerless at explaining reality, but assaults our intuitions of how reality should be. It seems likely the fault lies with our intuitions

By Daniel Cossins

Shutterstock/agsandrew

PARTICLES that also act like waves; the spooky action at a distance of entanglement; those dead-and-alive cats. Small wonder people often trot out physicist Richard Feynmans line that nobody understands quantum mechanics. With quantum theory, we have developed an exceedingly successful description of how fundamental reality works. It also amounts to a full-frontal assault on our intuitions about how reality should work.

Or does it? It only seems strange to us because our immediate everyday experience of the world is so very limited, says Sean Carroll at the California Institute of Technology. Intuitive-feeling classical physics is largely devoted to describing macroscopic objects the things we see and feel directly in the world around us. It should not be surprising that this breaks down when we push it into domains that we never experience directly, says Carroll.

There is a big difference between seeming strange and being strange, too. If quantum mechanics is right, it cant truly be strange its how nature works, says Carroll. You can say something similar, after all, about other areas of physics, such as Albert Einsteins space-and-time-warping theories of relativity. Their effects only truly kick in at close to light speed, or in humongous gravitational fields of the sort we never experience, so their picture of the world seems alien to us.

For all that, there does seem to be something peculiarly alien about quantum theory. Take the way the mathematics of the theory allows us only to know the probability, on average, of what we will find when we

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Why is quantum theory so strange? The weirdness could be in our heads - New Scientist

Pauli blocking, a quantum phenomenon that makes a dense quantum gas suddenly turn transparent, has now been observed in three independent experiments

By Leah Crane

Blue laser light being used to measure how quantum effects can influence light scattering in an ultracold gas of strontium atoms

Christian Sanner, Ye labs/JILA

If you get a dense quantum gas cloud cold enough, you can see right through it. This phenomenon, called Pauli blocking, happens because of the same effects that give atoms their structure, and now it has been observed for the first time.

This has been a theoretical prediction for more than three decades, says Amita Deb at the University of Otago in New Zealand, a member of one of three teams that have now independently seen this. This is the first time this been proven experimentally.

Pauli blocking occurs in gases made up of a type of particle called a fermion, a category that includes the protons, neutrons and electrons that make up all atoms. These particles obey a rule called the Pauli exclusion principle, which dictates that no two identical fermions can occupy the same quantum state in a given system.

The same effect is responsible for why you dont fall through the floor, says Brian DeMarco at the University of Illinois at Urbana-Champaign, who wasnt a member of any of the three teams that spotted it. This physics, which is very difficult to observe, is all around you and helps determine the structure and stability of matter.

Pauli blocking occurs when fermions in a gas are packed so closely together that all of the available quantum states are filled, in a form of matter called a Fermi sea. When that is the case, the particles become unable to move, so light cant impart momentum to them. Because light that is absorbed by the particles or bounces off them will impart momentum, the light is forced to shine right through without interacting with the gas.

This is a very basic phenomenon, but its sort of a devil to see, says Yair Margalit at the Massachusetts Institute of Technology, a member of one of the three teams. You need these extreme conditions to be able to see it high densities and ultra-low temperatures and it is difficult to get both of these at once.

The three groups all performed similar experiments with atoms caught in magnetic traps and then cooled to close to absolute zero. Each used a different atom, but found similar results: light scattering off the gases was significantly lower when they were cold and dense enough to form a Fermi sea.

It is a great thing that three experiments came out at the same time and poke at the problem from different directions, says Deb. The results of all three were consistent with one another.

The discovery could help researchers study atoms in high-energy, or excited, states, which tend to decay quickly. Imagine I take an excited atom from somewhere else and place it in this Fermi sea of atoms. When it tries to come back down from the excited state, there is nowhere for it to go, so the lifetime of that state is artificially enhanced, says Christian Sanner at the JILA research institute in Colorado, a member of one of the teams.

The phenomenon could also be useful in quantum computers, the researchers say. Thats because the atoms used in some of these devices can be extremely sensitive to incoming light, and preparing parts of the computers in a Fermi sea could decrease that sensitivity and help them maintain their quantum states for longer, increasing the stability of the machines.

Journal references: Science, DOI:10.1126/science.abh3483, DOI:10.1126/science.abh3470, DOI:10.1126/science.abi6153

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Strange quantum effect predicted 30 years ago has now been observed - New Scientist

Space is really, really big, and aliens are not magic. In my previous article, I introduced these two points as being critical for anyone inclined to believe that UFOs are spacecraft from a distant star system. (I am not so inclined.) They are also the most important points to consider if you want humanity to get out of the solar system. (I do.)

Last week, we covered the first point about the distances between the stars. This week, we are going after the second point, which forces us to deal with the physics problems involved in crossing those vast distances even if we do not know yet what their solution might be.

Given the insane scale of interstellar distances, how might we extrapolate from the physics we do understand to envisioning possible ways that aliens (or us in the future) could cross the cosmic void? There are a few possible solutions to the problem of interstellar travel.

Cryosleep. Depending on their biology, the lifespan of our hypothetical aliens might be shorter than the centuries-long journey required for slow, sub-light speed travel between the stars. That is certainly the case for us. One obvious answer to this dilemma is to do the bear-in-winter thing and just hibernate through the trip. Cryosleep technology would basically freeze the bodys metabolism (or at least slow it down) for the duration of the journey. Despite being a staple of science fiction, no one even has come close to getting this to work for higher animals (like mammals). Still, it is the kind of solution that doesnt require magical new physics to exist maybe just magical new biology. Also, if post-biological life is really a thing, then maybe some aliens switch to silicon-based machine forms, and thus the question of long timescales is no longer an issue.

Light sails. While no one has ever been blown down the street by a ray of sunlight, photons (light particles) do exert a force a push on matter. If you could extend a large enough and light enough sheet of material in space, you could use the sun to propel you through space. The idea of such solar sails has been around for a long time, but in 2016, Philip Lubin of UC-Santa Barbara proposed using giant and very powerful lasers, rather than the Sun, to provide the light for interstellar sailing. With a large enough laser positioned at the departure point, you could accelerate a sail and the ship tethered to it up to nearly the speed of light. That means you could cross the distance between nearby stars in years or decades, not centuries or millennia (or longer).

The billionaire astronomy philanthropist Yuri Milner was so taken with this idea that he gave $100 million to its development in a project called Breakthrough Starshot. The hitch for UFOs using this technology is that you need another giant laser located in the target star system to slow you down if you wanted to stop for a visit.

Wormholes. If the speed of light limits how fast you can travel through space, then maybe the best solution for interstellar travel is giving up on the through. That possibility was the gift Einstein gave us with his Theory of General Relativity (GR). In relativity, space is not an empty void. Merged with time into a single entity called spacetime, it constitutes a flexible fabric that can be bent, stretched, and folded. Wormholes represent a kind of spacetime tunnel that uses this folding to join two regions of the galaxy together that only appear to be widely separated.

While such wormholes (a.k.a., Einstein-Rosen bridges) are most definitely allowed in GR, they are unstable. That means once formed (by whatever means, natural or otherwise), they would almost instantly slam closed. So, if aliens want wanted to use wormholes to build a kind of galactic transit system, they would need to find something physicists call exotic matter. This is stuff that has true anti-gravity properties. It could force the two mouths of a wormhole to stay open, thereby connecting two distant parts of the galaxy. The big hitch here is that exotic matter is not real. It is just a term that you can add to the GR equations and change how they behave. But it is there, within the framework of known physics. If exotic matter turns out to be more than just a physicists pipedream, it could serve as the means for fast interstellar travel.

Warp drives (a.k.a., hyperdrives). Ah, warp drives, the darling of science fiction writers everywhere. If aliens could build a warp drive, they would once again be using the fabric of space idea from Einsteins GR. The drive does not push you through space from one place in the galaxy to the other. Instead, it creates a warp bubble that stretches and then relaxes the spacetime around you. You do not travel through space faster than light; instead, you warp and unwarp space faster than light speed. This is the killer app loophole in GR: While nothing can travel faster than the speed of light through space, spacetime itself can move at whatever speed it likes.

The nice thing about warp bubbles is that they, like wormholes, are also theoretically possible, as Miguel Alcubierre showed in a famous 1994 paper. The Alcubierre drive concept has received considerable attention since then and can be extended a number of ways. But there are, as you might expect, some really big problems with warp drives (or else we would have them already). Once again, you need that exotic matter stuff that probably does not exist. Even more problematic is that warp bubbles may generate huge shock waves of high energy gamma rays as they move. Once you dropped out of warp, this blast of energy would fry everything in your path and sterilize any planet you were visiting. If that is the case, lets hope that any Alcubierre drive-equipped aliens dont pop in for brunch anytime soon.

Quantum mechanics. Quantum physics, which is our uber-powerful theory of the atomic and sub-atomic world, is notoriously weird. With quantum mechanics, physicists are forced to talk about particles being in two places at the same time or two particles instantly affecting each other, even though they are on opposite sides of the Universe. I could go on for a while about how strange quantum mechanics is compared to our common sense understanding of how space, time, matter, and energy are supposed to behave. Even after 100 years of developing quantum mechanics into the most accurate and potent physical theory ever created and after becoming the ground upon which all our electronic miracles are built we still cannot say we understand what it is telling us about the nature of reality.

Personally, I think that is pretty cool. What all this means for interstellar travel is that there might be something hiding in quantum mechanics that allows you to bypass GRs apparent restrictions regarding spacetime. Some folks who are working on merging quantum mechanics and GR into a theory of quantum gravity even believe that spacetime may not be fundamental. Instead, it might emerge out of some deeper aspect of reality. So, quantum mechanics could have some tricks up its sleeve that a sufficiently advanced alien species might know about and exploit for interstellar travel. But be careful. There is no physics here other than noting some weirdness.

So thats it. Thats all we (or they) have in terms of solutions to the problems posed by interstellar travel. Now, a good science fiction writer might find other creative ways to imagine getting from one star to the next. The list above, however, pretty much exhausts what a scientist would propose as being possible based on what we know about reality (which is a lot). The important thing to note is that once you go past the first two possibilities, then Elvis, in terms of experimentally validated physics, has most definitely left the building.

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Interstellar travel: the technology we need to go long-distance - Big Think

image:The Oleynik team simulated a split elastic-inelastic shock wave moving through a single crystal diamond. view more

Credit: Jonathan Willman, Materials Simulation Laboratory, Oleyniks Group at USF

Are diamonds even stronger than weve ever imagined? Can other post-diamond phases appear when diamond is subjected to extreme pressures? A team used machine-learned descriptions of interatomic interactions on the 200-petaflop Summit supercomputer at theUS Department of Energys (DOEs)Oak Ridge National Laboratory(ORNL) to model more than a billion carbon atoms at quantum accuracy and observe how diamonds behave under some of the most extreme pressures and temperatures imaginable. The results are nothing short of incredible.

The team was led by scientists at the University of South Florida (USF), DOEs Sandia National Laboratories (Sandia), DOEsNational Energy Research Scientific ComputingCenter(NERSC), and the NVIDIA Corporation. The researchers found that under extreme conditions, a shock wave strongly compresses the diamond as it passes through and forces it to crack under the pressure.

The study will help scientists better understand how carbon behaves under extreme conditions. This understanding is crucial for inertial confinement fusion, in which hydrogen fuel is kept inside a diamond capsule and nuclear fusion reactions are initiated by compressing the collapsing diamond shell. It is also important for uncovering the internal structure of carbon-rich planetslike Uranusand carbon-rich exoplanets. Exoplanets exist around stars outside of our solar system, and observations suggest they can be rich in diamond and silica.

Observations have shown that some exoplanets consist of carbon-rich constituents, such as methane, which, upon compression, convert to diamond, said Ivan Oleynik, a professor of physics at USF and principal investigator on the project. To understand the structure of these exoplanets, scientists need to understand the behavior of carbon at extreme conditions.

Scientists had believed that under extreme temperatures and pressures, diamond can experience plasticity similar to metals. But as it turns out, diamond experiences a brittle behavior while sustaining its exceptional strength. The team found that these cracks are healed through the formation of amorphous carbon. This carbon is eventually converted into regions of hexagonal diamond, thus explaining the underlying mechanism of diamonds strength.

For this work, the team has been named a finalist for the Association for Computing Machinery Gordon Bell Prize. This prize has been awarded each year since 1987 at theInternational Conference for High-Performance Computing, Networking, Storage and Analysis(SC). It recognizes outstanding achievements inapplying high-performance computing (HPC) to challenges in science, engineering, and large-scale data analytics. The teamsresults will be presented at SC21, to be held November 1419, 2021, in St. Louis, MO.

Diamonds take the heat

Experiments at SandiasZ Pulsed Power Facilityand at Lawrence Livermore National Laboratory (LLNL)facilities capable of creating tens of millions of atmospheres, or 100s of millions of pounds per square inchhave shown that diamond retains extremely high strength even when subjected to enormous compression and heating. It retains this strength up to the state when it should start melting. These experiments involved pressures above several million atmospheres. However, there has been controversy around what actually happens to diamonds under such extreme pressures.

When you load diamond with enormous pressure, it was assumed to turn into a plastic-like state. But we know diamonds are brittle and dont behave in this way, Oleynik said. Our simulations have uncovered an unexpected mechanism of inelastic deformations. Diamond cracks when it is compressed by the enormous shock waves generated at these gigantic compression facilities. These cracks are then reformed during an amorphous-like carbon state inside these cracks. They are then followed by recrystallization into hexagonal stacking faults where the atomic planes are shifted, compared with those in ideal diamond crystals.

Under such extreme conditions, atoms are squeezed together so tightly that only quantum mechanics, which describes how materials behave at the atomic scale, can provide a sufficiently detailed picture of how they interact with one another. But using quantum mechanics to study the dynamics of atoms is computationally expensive.

If you want to simulate something approaching experimental length and timescales, such as micrometers and nanoseconds, you need millions and even billions of atoms and millions of molecular dynamics time steps. But with quantum mechanics, the largest amount of particles you can do is no more than 1,000 atoms. And the largest number of steps is 10,000.

The team made a major breakthrough in describing with quantum accuracy how carbon atoms interact under such enormous pressure and temperature. The team fingerprinted each atom in a diamond using a set of so-calleddescriptors, which were then used to construct an accurate representation of the systems potential energy using powerful machine-learning techniques. This innovative machine-learning approach enabled the team to make predictions of atomic-scale dynamics for a billion atoms to within 3 percent accuracy when compared with extremely precise quantum mechanical calculations.

GPUs illuminate new diamond properties

PhD student Jonathan Willman and postdoctoral associate Kien Nguyen-Cong, both in Oleyniks group at USF, performed the simulations on Summit using a billion-atom sample on the full machine for 24 hours.

Simulating billions of atoms at this nanometer timescale could only be done on Summit. GPU acceleration was the key to achieving these results, Oleynik said. Our team made a major algorithmic breakthrough that allowed our GPU-enabled code to run one hundred times faster than it does on CPU-only machines.

In these billion-atom simulations, the team observed for the first time the shock wave propagation in micrometer-thick diamond at fine resolution, down to the atomic scale. This allowed the team to observe details of diamond cracking and reforming, as well as complex interference patterns created by multiple local sound waves initiated at the crack tips.

We couldnt see this before because we had never done such grand-scale simulations, Oleynik said. The cross section of the diamond sample the team used in simulations is 100 by 100 nanometers and 1 micronor 1,000 nanometersin length.

Running the simulations at such a grand scale is important because now we can achieve high fidelity, and we can say for certain that our results are close to reality, Oleynik said.

Reaching an unknown phase of carbon

Thanks to Summit, the team also has a better understanding of why diamonds havent been transformed to the so-called BC8 high-pressure, post-diamond phase in billion-dollar experiments at the National Ignition Facility (NIF) at LLNL.

These experiments pursued conventional thinking of concerted transformation of atoms from a diamond lattice to that of the BC8 phase. This phase transition requires overcoming an enormous energy, Oleynik said. Our hypothesis, which was brilliantly confirmed in our billion-atom simulations, is that the liquid-like, amorphous carbon can facilitate the nucleation of the BC8 phase. This provides a viable pathway for synthesis of this post-diamond phase. Within the NIF Discovery Science program, we are working with our experimental collaborators to confirm our predictions.

The team plans to extend their simulations to even bigger, trillion-atom systems using emerging exascale HPC systems. These include the nations first exascale supercomputer,Frontierat theOak Ridge Leadership Computing Facility(OLCF), a DOEOffice of Scienceuser facility located at ORNL.

Such tour de force simulations will provide even deeper insight into mystery ofdiamond rainupon compression of methane inside of ice giants Uranus and Neptune, Oleynik said. The beauty of these simulations is that we can see how nature responds to these extreme pressures and temperatures at the atomic level. We can also see how individual atomic motions combine together in a collective macroscopic behavior, which can then be observed in state-of-the art experiments.

The team members include Jonathan Willman, Kien Nguyen-Cong, and Ivan Oleynik from USF; Stan Moore, Mitchell Wood, and Aidan Thompson from Sandia; Rahulkumar Gayatri from NERSC; and Evan Weinberg from the NVIDIA Corporation.

Sandia is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for DOEs National Nuclear Security Administration (NNSA).

The research is supported byNNSA; the Exascale Computing Project, a collaborative effort of the DOEs Office of Science and NNSA; and DOEs Advanced Scientific Computing Research Leadership Computing Challenge and Innovative and Novel Computational Impact on Theory and Experiment awards. This research used resources of NERSC and the OLCF.

Related Publication:Nguyen-Cong, Kien, Jonathan T. Willman, Stan G. Moore, Anatoly B. Belonoshko, Rahulkumar Gayatri, Evan Weinberg, Mitchell A. Wood, Aidan P. Thompson, and Ivan I. Oleynik. Billion Atom Molecular Dynamics Simulations of Carbon at Extreme Conditions and Experimental Time and Length Scales. Paper to be presented at SC21: The International Conference for High Performance Computing, Networking, Storage and Analysis, St. Louis, MO, November 2021.

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Team earns Gordon Bell prize finalist nomination for simulating carbon at extreme pressures and temperatures - EurekAlert

By New Scientist

Science is very good at explaining the how how the planets revolve around the sun on elliptical orbits, how evolution by natural selection produces the vast diversity of life forms that we see, and so on. Its far less good at answering the why? why are things as they are?

To celebrate New Scientists 65th anniversary, well attempt to fill in that gap, plunging into the twilight zone where science meets metaphysics and philosophy as we peel back layers of understanding to find deeper truths about some of the most mysterious questions surrounding life, the universe and everything. Or, more likely, more onion.

The concept of the big bang revolutionised 20th-century cosmology. But the idea that the universe began from this point, a case of something from nothing, seems increasingly unlikely.

We are tiny specks of life in a vast, indifferent cosmos but to say that decreases the value of our existence is to measure ourselves against the wrong thing.

Dig down, and evolution by natural selection is just about spontaneous, sustained accumulation of complexity if life elsewhere exists, its likely to develop in the same way.

The one-way flow of time is one of the great mysteries of physics. It might be that we see causes and effects just because our information about reality is incomplete.

The human capacity for both good and evil has long mystified philosophers. Evolutionary biology suggests they are both offshoots of one of our oddest character traits.

Physicists have long speculated why our universe seems just right for life. The most complex answer might be the simplest that every other universe also exists.

Its easy to think human conscious experience is unique, but a better understanding of consciousnesss mysteries comes by tracing it back in the evolutionary tree.

Its easy to think human conscious experience is unique, but a better understanding of consciousnesss mysteries comes by tracing it back in the evolutionary tree.

Quantum theory is peerless at explaining reality, but assaults our intuitions of how reality should be. It seems likely the fault lies with our intuitions.

Nothing in the cosmos can travel faster than light speed. By distinguishing cause and effect and stopping everything happening in a jumbled mess, our existence depends on it.

Myths and stories trump rational reasoning when it comes to analysing distant threats like climate change. But we have tools to combat that and its a myth irrationality is on the rise.

The search for extraterrestrial intelligence has been going on for 60 years without success. Given the hurdles to interstellar communication, thats just a blink of an eye.

We have made huge progress in understanding some bits of the cosmos, but weve hit a brick wall with things like quantum theory and our own minds. Is there a way round?

More on these topics:

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13 of the most profound questions about the cosmos and ourselves - New Scientist

German acting Chancellor Angela Merkel attends a joint news conference with Greek Prime Minister Kyriakos Mitsotakis (not pictured) at the Maximos Mansion, in Athens, Greece, October 29, 2021. REUTERS/Alkis Konstantinidis

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BERLIN, Nov 17 (Reuters) - European countries must work together on next-generation chip manufacturing, Angela Merkel said, drawing on her 16 years of experience in the highest office to warn that no European country could stay at the forefront of high-tech on its own.

The outgoing German chancellor told Reuters in an interview that the costs of moving to the next level in areas from chip development to cloud and quantum computing and battery production meant that the private sector would need state support.

Merkel herself conducted fundamental research in quantum chemistry in East Germany before entering politics after German reunification in 1990. She pointed to Korea, Taiwan and U.S. President Joe Biden's stimulus package as examples of what was possible.

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"The state will have to play a significant role. South Korea and Taiwan go to show that competitive chip production in the 3- or 2-nanometer range, for example, is essentially impossible without state subsidies," she said.

The global economy's current struggle to restore supply chains snapped by resource shortages and the coronavirus pandemic further highlights the need to ensure that Europe has its own production facilities in key areas, she said.

But she also lamented the failure of German companies to capitalise on an outstanding research base.

In particular, she said she was "shocked" at German companies' lack of interest in quantum computing, even though Germany was a world leader in research in a field that could make computers faster and more powerful than ever before.

NO ALEXA FOR ANGELA

She said her government had made steps towards improving Germany's innovation and start-up cultures, pointing to a German-led project to create a secure and efficient cloud data infrastructure for Europe, named Gaia-X.

"But in the long term it cannot be the state that drives new developments," the European Union's longest-serving leader said.

Germany's sprawling, decentralised government structure could also be a hindrance to innovation.

Merkel said the presence of an ethics council and data protection officer in each of the 16 federal states put a heavy burden on firms in life sciences, for instance, where Germany had fallen behind.

It was, however, at the leading edge of research in areas such as quantum physics, climate research, physics, chemistry and robotics, she said.

Not that the same could be said for Merkel's own use of home technology.

"Im happy enough when I can set up a delayed start on my washing machine, but beyond that, to be honest, I have neither the time nor the inclination to have my whole home remote-controlled," she said.

"Maybe Ill develop an interest when I have more time in the near future."

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Reporting by Andreas Rinke in Berlin; Writing by Thomas Escritt; Editing by Kevin Liffey

Our Standards: The Thomson Reuters Trust Principles.

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EXCLUSIVE Europe must work together to stay at forefront of high-tech - Merkel - Reuters