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Category Archives: Quantum Physics
Posted: October 27, 2019 at 2:48 pm
If you could look closely enough at the objects that surround you, zooming in at magnifications far beyond those you could ever see with most microscopes, you would eventually get to a point where the familiar rules of your everyday experiences break down. At scales where blood cells and viruses seem enormous and molecules come into view, things are no longer subject to the simple laws of physics that we learn in high school.
Atomsand the electrons, protons and neutrons they are made ofdont exist in the same way a marble does. Instead they are smeared in clouds that are difficult to understand and impossible to describe without the complex mathematics of quantum mechanics.
And yet atoms make up molecules, which, in turn, are the building blocks of marbles and everything else we touch and see each day. Nature has clearly found some way of suppressing quantum behavior when quantum objects are assembled into the familiar ones all around us.
How can things that obey the classical laws of physicssuch as a pitched baseball or a bumblebee in flightbe composed of parts that are subject to quantum rules at minute levels? That is one of the deepest questions in modern physics. In pursuit of an answer, recent researchwith funding from the High Energy Physics program at the Department of Energys Office of Scienceshould help shed light on how the classical world emerges from the underlying quantum one.
A quantum-computing algorithm, developed by scientists at Los Alamos National Laboratory and the University of California, Davisincluding both of usopens a new window on the connection between the quantum and classical worlds and the transition that must occur as we zoom out from the smallest scales.
To study the quantum-to-classical transition, physicists need to evaluate how close a quantum system is to acting classically. Among other effects, physicists must consider the fact that quantum objects are subject to wave-particle duality. Things we often think of as particles, such electrons, can act like waves in some circumstances. And things we think of as waves, such as light, can act like particles, which are called photons. In a quantum system, the wavelike states of particles can interfere with one another in much the same way that ocean waves can sometimes add together or cancel one another out.
A quantum system lacking interference can be described using classical rules rather than quantum ones. The newly developed algorithm searches out interference-free solutions, known as consistent histories, which are those we ultimately observe in the classical world we inhabit.
For systems of a few atoms, finding consistent histories is fairly trivial. For systems made up of many pieces, however, quantum-to-classical transition calculations are notoriously difficult to solve. The number of equations involved grows drastically with each added atom. In fact, for systems of more than just a few atoms, calculations rapidly become intractable on even the most powerful supercomputers.
Appropriately enough, the new consistent-histories algorithm relies on a quantum computer to overcome the computational explosion and gauge how close to classical a quantum system is behaving. Unlike conventional computers that manipulate data made up of 1s and 0s, quantum computers store and manipulate data as quantum combinations of numbers. Similar to how an atom exists as a quantum cloud rather than at a single point, data in a quantum computer is not a single number but a superposition of many numbers.
While quantum computers powerful enough to solve meaningful problems dont exist just yet, it has been theoretically shown that they can achieve remarkable calculations, performing, in principle, exponentially faster than conventional computers. Using the consistent-histories algorithm, quantum computers have the potential to tame the difficulties of studying the quantum-to-classical transition precisely because they operate under the same rules that govern atoms and other quantum entitiesan elegant potential solution to a problem that has vexed physicists for decades.
Posted: at 2:48 pm
Scientists at Google on Wednesday declared, via a paper in the journal Nature, that theyd done something extraordinary. In building a quantum computer that solved an incredibly hard problem in 200 seconds a problem the worlds fastest supercomputer would take 10,000 years to solve theyd achieved quantum supremacy. That is: Googles quantum computer did something that no conventional computer could reasonably do.
Computer scientists have seen quantum supremacy the moment when a quantum computer could perform an action a conventional computer couldnt as an elusive, important milestone for their field. There are many research groups working on quantum computers and applications, but it appears Google has beaten its rivals to this milestone.
According to John Preskill, the Caltech particle physicist who coined the term quantum supremacy, Googles quantum computer is something new in the exploration of nature. These systems are doing things that are unprecedented.
Of note: Some researchers at IBM contest the supremacy claim, saying that a traditional supercomputer could solve the problem in 2.5 days, not 10,000 years. Still, 200 seconds is a lot quicker than 2.5 days. If the quantum computer isnt supreme, its still extremely impressive because its so small and so efficient. They got one little chip in the quantum computer and the supercomputer is covering a basketball court, Preskill says.
It sounds all very gee-whiz. And some scientists think these computers will one day lead to discoveries of new drugs and possibly whole new fields of chemistry. Others fear theyll be used one day to crack the toughest security protocols.
But if youve never heard of a quantum computer or know what it does or what its used for, youre not alone. So lets break it down.
Before we discuss what a quantum computer is, its helpful to think about what a traditional computer is.
Traditional computers utilize the flow of electricity and can be turned on or off at switches inside circuits. Whether a switch is on or off generates the ones and zeros that underlie all computer code. This is what Alan Turing discovered in his pioneering work: Simple rules for turning those switches on and off can be used to solve any mathematical problem. These zeros and ones are called bits, and they are the smallest bit of information a computer stores.
To recap: Traditional computers use the physics of electricity, namely the fact that its flow can be turned on and off at switches, to run everything.
Quantum computers, on the other hand, are not built upon using the flow of electricity. They rely instead on the physical properties of electrons, photons, and other tiny bits of matter that are subject to the laws of quantum mechanics.
These bits of matter can do a lot more than just be turned on and off. Actually, on and off arent really words that make sense in quantum physics.
This kind of tiny matter is best described in states called amplitudes (like waves, since the tiniest bits of matter can act as both particles and waves). A particle can have two different amplitudes at the same time a state called superposition. They can also be entangled, meaning a change in one particle instantly changes another. The amplitudes of particles can also cancel one another out like opposing waves in water would. Also, the smallest particles in nature dont really exist in a point in space but they exist as a probability of existing.
For a great video explainer on quantum mechanics, check out this video by physicist Dominic Walliman.
Its all weird stuff that defies normal logic! Yet, there is a logic to it. Out of this chaotic mess of entanglement, superposition, and interference, our stable world arises.
Quantum mechanics are the rules that make reality, says Scott Aaronson, a theoretical computer scientist who studies quantum computing at the University of Texas Austin. Take an electron, he says. According to classical physics (think Newtons laws of motion), electrons should spiral into the center of atoms, rendering them useless. What quantum mechanics ultimately says is there are all these pathways where the electron can spiral into the nucleus, but they all cancel each other out.
Its hard to think about, no doubt. Its staggering what were talking about, Aaronson says. Its like the electron itself is a computer, sorting through all the possible paths it can take before finding the right ones. In a sense, the electron has solved the problem of its own existence.
Amazingly, what quantum computer engineers are doing is tapping into the chaotic logic of the quantum world to solve problems. Like a normal computer with its switches to control the flow of electricity, they build hardware to influence quantum states. (A part of the research into quantum computing is figuring out what the optimal hardware should be.) Theyre trying to choreograph quantum interactions in a way so the wrong answers to big problems get canceled out.
In a normal computer, a bit can be in two states on or off. Zero or one. But a qubit a.k.a. a quantum bit can be in many states at once. That means a single qubit can contain exponentially more information than a normal bit.
Thats a bit like having four regular computers running side by side, Cosmos magazine explains. If you add more bits to a regular computer, it can still only deal with one state at a time. But as you add qubits, the power of your quantum computer grows exponentially.
What it boils down to is that a quantum computer can crunch through some enormous problems really quickly. For instance, a lot of cybersecurity depends on computers multiplying huge prime numbers. Its really really hard for traditional computers to reverse this process, to find the prime numbers that resulted in the bigger number and crack the encryption. But quantum computers could. In a quantum computing world, we may need even stronger security protections, perhaps even those derived from quantum mechanics itself.
Scientists hope quantum computers may lead to better, quicker ways to solve optimization problems. When you have many different choices in front of you, how do you choose the ideal path? These types of questions strain traditional computers but could, potentially, be a breeze for quantum computers, which could sort through all the possible parts at once. A traditional computer has to try out each path one at a time. Though, were not going to be able to run applications like that for a while because the hardware just isnt advanced enough, Preskill adds.
Quantum computers are hard to build, are prone to generating errors, and their components are often unstable. Right now, Preskill says, what Google has shown is a proof of concept: that quantum computers can solve problems in a way traditional computers cant. Its machine runs 54 qubits. But this is a tiny fraction of the one million qubits that could be needed for a general-purpose machine, a news article at Nature states.
Quantum computers dont really do anything practical yet. The test problem Google ran for their paper was and this is a simplification to see if a random number generator was truly random.
Theyre validating that their hardware is doing what they think its supposed to be doing, Preskill says, checking that with the quantum computer they can perform the computation with many fewer steps and much faster than a classical computer.
Perhaps most of the more immediate uses would just be to use quantum computers to simulate the frenzied world of quantum mechanics and better understand it.
We can use a quantum computer as a general simulator of nature on the microscopic scale, Aaronson says, and use it to predict what a protein will do, help design a drug that will bind to a receptor in the right way, and help design new chemical reactions ... design better batteries. You would only need one or two successes to make this whole thing worthwhile.
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Posted: at 2:48 pm
Its the one aspect of reality we all take for granted: an object exists in the world regardless of whether youre looking at it.
But theoretical and quantum physicists have been struggling for years with the possibly of a many worldsinterpretation of reality, which suggests that every time two things could happen, it splits into new parallel realities.Essentially, they think youre living in one branch of a complex multiverse meaning that there are a near-infinite number of versions of you that could have made every conceivable alternate choice in your life.
Physicist Sean Carroll from the California Institute of Technology deals with this problem in his new book Something Deeply Hidden. In a new interview with NBC, Carroll makes his stance on the matter clear:he thinks the many worlds hypothesis is a definite possibility.
Its absolutely possible that there are multiple worlds where you made different decisions,he told the network. Were just obeying the laws of physics.
So if there are multiple worlds, how many are there?
We dont know whether the number of worlds is finite or infinite, but its certainly a very large number, Carroll claimed. Theres no way its, like, five.
And he goes further,into a metaphysical view of the universe in which physical reality has much to do with the observer.
Before you look at an object, whether its an electron, or an atom or whatever, its not in any definite location, Carroll told NBC. It might be more likely that you observe it in one place or another, but its not actually located at any particular place.
Carroll isnt the only one that has examined the possibility of many alternate realities. The likes of Stephen Hawking and Erwin Schrdinger have suggested that many other parallel worlds exist as well.
In his most recent work work, Hawking suggested that thanks to quantum mechanics, the Big Bang supplied us with an endless number of universes, not just one.
As for the ability to visit other parallel universes, a topic thats come up countless times in science fiction, Carroll is not hopeful.
[Alternate universes] dont interact, they dont influence each other in any form, he said. Crossing over is like traveling faster than the speed of light. Its not something that you can do.
READ MORE: The weirdest idea in quantum physics is catching on: There may be endless worlds with countless versions of you. [NBC]
More on parallel universes: Parallel Universes Could Solve One of the Biggest Mysteries in Physics
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Posted: at 2:48 pm
Credit: Christine Daniloff, MIT, ESA/Hubble and NASA
As the Big Bang theory goes, somewhere around 13.8 billion years ago the universe exploded into being, as an infinitely small, compact fireball of matter that cooled as it expanded, triggering reactions that cooked up the first stars and galaxies, and all the forms of matter that we see (and are) today.
Just before the Big Bang launched the universe onto its ever-expanding course, physicists believe, there was another, more explosive phase of the early universe at play: cosmic inflation, which lasted less than a trillionth of a second. During this period, matter a cold, homogeneous goop inflated exponentially quickly before processes of the Big Bang took over to more slowly expand and diversify the infant universe.
Recent observations have independently supported theories for both the Big Bang and cosmic inflation. But the two processes are so radically different from each other that scientists have struggled to conceive of how one followed the other.
Now physicists at MIT, Kenyon College, and elsewhere have simulated in detail an intermediary phase of the early universe that may have bridged cosmic inflation with the Big Bang. This phase, known as reheating, occurred at the end of cosmic inflation and involved processes that wrestled inflations cold, uniform matter into the ultrahot, complex soup that was in place at the start of the Big Bang.
The postinflation reheating period sets up the conditions for the Big Bang, and in some sense puts the bang in the Big Bang, says David Kaiser, the Germeshausen Professor of the History of Science and professor of physics at MIT. Its this bridge period where all hell breaks loose and matter behaves in anything but a simple way.
Kaiser and his colleagues simulated in detail how multiple forms of matter would have interacted during this chaotic period at the end of inflation. Their simulations show that the extreme energy that drove inflation could have been redistributed just as quickly, within an even smaller fraction of a second, and in a way that produced conditions that would have been required for the start of the Big Bang.
The team found this extreme transformation would have been even faster and more efficient if quantum effects modified the way that matter responded to gravity at very high energies, deviating from the way Einsteins theory of general relativity predicts matter and gravity should interact.
This enables us to tell an unbroken story, from inflation to the postinflation period, to the Big Bang and beyond, Kaiser says. We can trace a continuous set of processes, all with known physics, to say this is one plausible way in which the universe came to look the way we see it today.
The teams results appear today in Physical Review Letters. Kaisers co-authors are lead author Rachel Nguyen, and John T. Giblin, both of Kenyon College, and former MIT graduate student Evangelos Sfakianakis and Jorinde van de Vis, both of Leiden University in the Netherlands.
The theory of cosmic inflation, first proposed in the 1980s by MITs Alan Guth, the V.F. Weisskopf Professor of Physics, predicts that the universe began as an extremely small speck of matter, possibly about a hundred-billionth the size of a proton. This speck was filled with ultra-high-energy matter, so energetic that the pressures within generated a repulsive gravitational force the driving force behind inflation. Like a spark to a fuse, this gravitational force exploded the infant universe outward, at an ever-faster rate, inflating it to nearly an octillion times its original size (thats the number 1 followed by 26 zeroes), in less than a trillionth of a second.
Kaiser and his colleagues attempted to work out what the earliest phases of reheating that bridge interval at the end of cosmic inflation and just before the Big Bang might have looked like.
The earliest phases of reheating should be marked by resonances. One form of high-energy matter dominates, and its shaking back and forth in sync with itself across large expanses of space, leading to explosive production of new particles, Kaiser says. That behavior wont last forever, and once it starts transferring energy to a second form of matter, its own swings will get more choppy and uneven across space. We wanted to measure how long it would take for that resonant effect to break up, and for the produced particles to scatter off each other and come to some sort of thermal equilibrium, reminiscent of Big Bang conditions.
The teams computer simulations represent a large lattice onto which they mapped multiple forms of matter and tracked how their energy and distribution changed in space and over time as the scientists varied certain conditions. The simulations initial conditions were based on a particular inflationary model a set of predictions for how the early universes distribution of matter may have behaved during cosmic inflation.
The scientists chose this particular model of inflation over others because its predictions closely match high-precision measurements of the cosmic microwave background a remnant glow of radiation emitted just 380,000 years after the Big Bang, which is thought to contain traces of the inflationary period.
The simulation tracked the behavior of two types of matter that may have been dominant during inflation, very similar to a type of particle, the Higgs boson, that was recently observed in other experiments.
Before running their simulations, the team added a slight tweak to the models description of gravity. While ordinary matter that we see today responds to gravity just as Einstein predicted in his theory of general relativity, matter at much higher energies, such as whats thought to have existed during cosmic inflation, should behave slightly differently, interacting with gravity in ways that are modified by quantum mechanics, or interactions at the atomic scale.
In Einsteins theory of general relativity, the strength of gravity is represented as a constant, with what physicists refer to as a minimal coupling, meaning that, no matter the energy of a particular particle, it will respond to gravitational effects with a strength set by a universal constant.
However, at the very high energies that are predicted in cosmic inflation, matter interacts with gravity in a slightly more complicated way. Quantum-mechanical effects predict that the strength of gravity can vary in space and time when interacting with ultra-high-energy matter a phenomenon known as nonminimal coupling.
Kaiser and his colleagues incorporated a nonminimal coupling term to their inflationary model and observed how the distribution of matter and energy changed as they turned this quantum effect up or down.
In the end they found that the stronger the quantum-modified gravitational effect was in affecting matter, the faster the universe transitioned from the cold, homogeneous matter in inflation to the much hotter, diverse forms of matter that are characteristic of the Big Bang.
By tuning this quantum effect, they could make this crucial transition take place over 2 to 3 e-folds, referring to the amount of time it takes for the universe to (roughly) triple in size. In this case, they managed to simulate the reheating phase within the time it takes for the universe to triple in size two to three times. By comparison, inflation itself took place over about 60 e-folds.
Reheating was an insane time, when everything went haywire, Kaiser says. We show that matter was interacting so strongly at that time that it could relax correspondingly quickly as well, beautifully setting the stage for the Big Bang. We didnt know that to be the case, but thats whats emerging from these simulations, all with known physics. Thats whats exciting for us.
This research was supported, in part, by the U.S. Department of Energy and the National Science Foundation.
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The weirdest idea in quantum physics is catching on: There may be endless worlds with countless versions of you. – NBC News
Posted: October 24, 2019 at 11:29 am
Ever wonder what would have happened if you'd taken up the "Hey, let's get coffee" offer from that cool classmate you once had? If you believe some of todays top physicists, such questions are more than idle what-ifs. Maybe a version of you in another world did go on that date, and is now celebrating your 10th wedding anniversary.
The idea that there are multiple versions of you, existing across worlds too numerous to count, is a long way from our intuitive experience. It sure looks and feels like each of us is just one person living just one life, waking up every day in the same, one-and-only world.
But according to an increasingly popular analysis of quantum mechanics known as the many worlds interpretation, every fundamental event that has multiple possible outcomes whether its a particle of light hitting Mars or a molecule in the flame bouncing off your teapot splits the world into alternate realities.
Even to seasoned scientists, its odd to think that the universe splits apart depending on whether a molecule bounces this way or that way. Its odder still to realize that a similar splitting could occur for every interaction taking place in the quantum world.
Things get downright bizarre when you realize that all those subatomic splits would also apply to bigger things, including ourselves. Maybe theres a world in which a version of you split off and bought a winning lottery ticket. Or maybe in another, you tripped at the top of a cliff and fell to your death oops.
It's absolutely possible that there are multiple worlds where you made different decisions. We're just obeying the laws of physics, says Sean Carroll, a theoretical physicist at the California Institute of Technology and the author of a new book on many worlds titled "Something Deeply Hidden." Just how many versions of you might there be? We don't know whether the number of worlds is finite or infinite, but it's certainly a very large number," Carroll says. "Theres no way its, like, five.
Carroll is aware that the many worlds interpretation sounds like something plucked from a science fiction movie. (It doesnt help that he was an adviser on "Avengers: Endgame.") And like a Hollywood blockbuster, the many worlds interpretation attracts both passionate fans and scathing critics.
Renowned theorist Roger Penrose of Oxford University dismisses the idea as reductio ad absurdum: physics reduced to absurdity. On the other hand, Penroses former collaborator, the late Stephen Hawking, described the many worlds interpretation as self-evidently true.
Carroll himself is comfortable with the idea that hes but one of many Sean Carrolls running around in alternate versions of reality. The concept of a single person extending from birth to death was always just a useful approximation, he writes in his new book, and to him the many worlds interpretation merely extends that idea: The world duplicates, and everything within the world goes along with it.
The mind-bending saga of the many worlds interpretation began in 1926, when Austrian physicist Erwin Schrdinger mathematically demonstrated that the subatomic world is fundamentally blurry.
In the familiar, human-scale reality, an object exists in one well-defined place: Place your phone on your bedside table, and thats the only spot it can be, whether or not you're looking for it. But in the quantum realm, objects exist in a smudge of probability, snapping into focus only when observed.
Before you look at an object, whether it's an electron, or an atom or whatever, it's not in any definite location, Carroll says. It might be more likely that you observe it in one place or another, but it's not actually located at any particular place.
Nearly a century of experimentation has confirmed that, strange as it seems, this phenomenon is a core aspect of the physical world. Even Einstein struggled with the notion: What happened to all of the other possible locations where the object could have been, and all the other different outcomes that could have ensued? Why should an objects behavior depend on whether or not somebody was looking at it?
In 1957, a Princeton student named Hugh Everett III came up with a radical explanation. He proposed that all possible outcomes really do occur but that only a single version plays out in the world we inhabit. All the other possibilities split off from us, each giving rise to its own separate world. Nothing ever goes to waste, in this view, since everything that can happen does happen in some world.
For decades, Everetts colleagues mostly brushed aside his explanation, treating it more like a ghost story than serious science. But nobody has found any flaws in Schrdingers equation; nor can they explain away its implications. As a result, many contemporary physicists including David Deutsch at Oxford University and Max Tegmark at the Massachusetts Institute of Technology have come to agree with Carroll that the many worlds interpretation is the only coherent way to understand quantum mechanics.
The many worlds interpretation raises all kinds of puzzling questions about the multiple versions of reality, and about the multiple versions of you that exist in them. Carroll has some answers.
If new universes are constantly popping into existence, isnt something being created from nothing, violating one of the most basic principles of physics? Not so, according to Carroll: It only looks like you are creating extra copies of the universe. It's better to think of it as taking a big thick universe and slicing it.
Why do we experience one particular reality but none of the others? What other one would you find yourself in? Carroll says, amused. Its like asking why you live now instead of some other time. Everyone in every world thinks that they're in that world.
Carroll also has a disappointing response for one of the most compelling questions of all: Could you cross over and visit one of the other realities and compare notes with an alternate-world version of yourself? Once the other worlds come into existence, they go their own way, Carroll says. They don't interact, they don't influence each other in any form. Crossing over is like traveling faster than the speed of light. It's not something that you can do.
One criticism of the many worlds interpretation is that while it offers a colorful way to think about the world, it doesnt deliver any new insights into how nature works. It is completely content-less, says physicist Christopher Fuchs of the University of Massachusetts, Boston.
Fuchs favors an alternative called Quantum Bayesianism, which offers a path back to an old-fashioned single reality. He argues that the universe changes when you look at it not because you are creating new worlds but simply because observation requires interacting with your surroundings. No coffee dates, no other lives for you. In this way, measurement is demoted from being something mystical to being about things as mundane as walking across a busy street: Its an action I can take that clearly has consequences for me, he says.
Coming at the critique from a different angle, Oxford's Roger Penrose argues that the whole idea of many worlds is flawed, because its based on an overly simplistic version of quantum mechanics that doesnt account for gravity. The rules must change when gravity is involved, he says.
In a more complete quantum theory, Penrose argues, gravity helps anchor reality and blurry events will have only one allowable outcome. He points to a potentially decisive experiment now being carried out at the University of California, Santa Barbara, and Leiden University in the Netherlands that's designed to directly observe how an object transforms from many possible locations to a single, fixed reality.
Carroll is unmoved by these alternative explanations, which he considers overly complicated and unsupported by data. The notion of multiple yous can be unnerving, he concedes. But to him the underlying concept of many worlds is crisp, clear, beautiful, simple and pure.
If he's right, he's not the only Sean Carroll who feels that way.
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Posted: at 11:29 am
Rapid changes are occurring in the field of artificial intelligence (AI) as many computer scientists explore new ways to make systems faster and more efficient. One anticipated capability is quantum computingtechnology that follows the laws of quantum physics, enabling processing power to exist in multiple states and perform multiple tasks at the same time. If realized in hardware, it would speed-up some computational problem-solving exponentially. UC San Diego Theoretical Physicist Max Di Ventra is catching this next wave of cutting-edge AI with an alternative and fundamentally different platform he calls memcomputing, which doesn't require quantum capabilities.
Sketch of a memcomputing architecture. Apart from the input/output and a control unit, which directs the machine on what problem to solve, all computation is done by a memory unit, a computational memory. From F.L. Traversa and M. Di Ventra, IEEE Trans. Neural Networks Learn. Sys. 26, 2702 (2015). 2015 IEEE.
Using a physics-based approach, this novel computing paradigm employs memory to both process and store information on the same physical location, a property that somewhat mimics the computational principles of the human brain, said the UC San Diego physics professor and author of The Scientific Method: Reflections from a Practitioner (Oxford University Press, 2018).
After years of trial and error, Di Ventra and his group developed all of the mathematics required for this new simple architecture, combining memory and compute anddriven by a specialized computational memory unit, with performance that resembles quantum computingwithout the overwhelming computational overhead. Now, with half-a-million dollars over 18 months from the Defense Advanced Research Projects Agency (DARPA), Di Ventra and his students are working to apply this new physics-based approach to AI.
Our project, if successful, would have a large impact in the field of machine learning and artificial intelligence by showing that physics approaches can be of great help in fields of research that are traditionally dominated by computer scientists, said Di Ventra.
With the DARPA funds, the team will apply memcomputing to the unsupervised learning, or pre-training, of Deep Belief Networks. These are systems of multi-layer neural networks (NNs) used to recognize, generate and group data. DiVentra will also propose a hardware architecture, using current technologies, to perform this task. Pre-training of NNs is a notoriously difficult problem, and researchers have all but abandoned it in favor of supervised learning. However, in order to have machines that adapt to external stimuli in real time and make decisions according to the context in which they operatethe goal of the third wave of AIpowerful new methods to train NNs in an unsupervised manner are required.
Demonstration that a memcomputing solver (named Falcon in the figure) outperforms, by orders of magnitude, state-of-the-art algorithms in solving difficult computational problems. From F. Sheldon, P. Cicotti, F.L. Traversa and M. Di Ventra, IEEE Trans. Neural Networks Learn. Sys. (2019). 2019 IEEE.
Di Ventra explained that memcomputing accelerates the time to find feasible solutions to the most complex optimization problems in all industries.
We have applied these emulations to a wide variety of difficult computational problems that are of interest to both academia and industry, and solved them orders of magnitude faster than traditional algorithms, noted Di Ventra.
Unlike quantum computing, memcomputing employs non-quantum units so it can be realized in hardware with available technology and emulated in software on traditional computers. Current computing capabilities began with the work of Alan Turing, who helped decrypt German codes during WWII with his Bombe Machine. He also developed the Turing Machine, which became the basis for modern computers. John von Neumann devised the architecture for the Turing Machine, whereby the central processing unit (CPU) was separate from the memory unit. The so-called von Neumann Bottleneck in todays computing is created precisely from the physical separation of the CPU and the memory unit: the CPU has to constantly insert and extract information from the memory, significantly slowing processing time.
Memcomputing represents a radical departure from both our traditional computers, and algorithms that run on them, and quantum computers, said Di Ventra. It provides the necessary tools for the realization of an adaptable computational platform deployable in the field of artificial intelligence and offers strategic advantages to the Department of Defense in numerous applications, said Di Ventra.
In view of the preliminary successes of memcomputing, Di Ventra has co-founded the company MemComputing, Inc., whichis developing a software as a service, based on this technology, to solve the most challenging problems in academia and industry.
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Posted: at 11:29 am
A persistent cosmological puzzle has been troubling physicists since 1917: what is the universe made of?
Complicating this already-mind-boggling question is the fact that our best theories conflict with our observations of the universe. Albert Einstein, according to scientific folklore, felt a unique responsibility for introducing this entire problem, reportedly referring to it as his "biggest blunder."
Essentially, Einstein's novel theory of general relativity didnt hold up when used to describe the universe as a whole. General relativity described the "geometry" of spacetime as being a trampoline-like surface; planets are heavy bowling balls that distort the surface, creating curves. If a less heavy ball (like a marble) was placed near the bowling ball, it would roll along the surface just like the motion of planets in orbit. Thus, orbits are explained not by a gravitational force but by curvature in spacetime.
This proposal worked when considering small regions of spacetime. But when Einstein applied it to the entire universe, its predictions didn't fit. So, Einstein introduced the "cosmological constant," a fixed value that represents a kind of anti-gravity, anti-mass, and anti-energy, counteracting gravitys effects. But when scientists discovered that the universe was expanding rather than static, as Einstein had believed, the cosmological constant was set to zero and more or less ignored. After we learned that the universes expansion is accelerating, however, scientists could no longer conveniently cancel out Einsteins anti-gravity suggestion.
What was previously assumed to be empty space in the universe now had to be filled with huge amounts of mysterious anti-energy in order to explain observations of the universes ever-quickening expansion. Even so, observations of the universes expansion suggest that the energy is 60 to 120 orders of magnitude lower than what recent quantum field theory predicts.
What this means is that all of this extra energy is somehow missing when we look at the universe as a whole; either its effectively hidden or very different in nature to the energy we do know about.
Today, theoretical physicists are trying to reconcile these mysteries by examining the structure of so-called spacetime in the universe at the smallest possible scale, with surprising findings: spacetime might not be the trampoline-like plane scientists once envisionedit might be a foamy mess of bubbles all containing mini-universes living and dying inside our own.
What is spacetime foam?
To try and solve the mystery of what fills the universe, scientists have been exploring the possibility that it's actually full of bubbles.
In 1955, influential physicist John Wheeler proposed that, at the quantum level, spacetime is not constant but "foamy," made up of ever-changing tiny bubbles. As for what these bubbles are "made" of, recent work suggests that spacetime bubbles are essentially mini-universes briefly forming inside our own.
The spacetime foam proposal fits nicely with the intrinsic uncertainty and indeterminism of the quantum world. Spacetime foam extends quantum uncertainty in particle position and momentum to the very fabric of the universe, so that its geometry is not stable, consistent, or fixed at a tiny scale.
Wheeler illustrated the idea of spacetime foam using an analogy with the surface of the ocean, as retold by theoretical physicist Y. Jack Ng at the University of North Carolina, Chapel Hill, in an email:
Imagine yourself flying a plane over an ocean. At high altitudes the ocean appears smooth. But as you descend, it begins to show roughness. Close enough to the ocean surface, you see bubbles and foam. Analogously, spacetime appears smooth on large scales; but on sufficiently small scales, it will appear rough and foamy.
Professor Steven Carlip at University of California, Davis, published new research in September that builds on Wheeler's quantum foam theory to show that spacetime bubbles could hide the cosmological constant at a large scale.
There are so many different proposals [to solve the cosmological constant problem], and a good sign for my research is that none of them is very widely accepted, Carlip said in an interview. I thought it was worth looking for an approach that was less ad hoc, that might come from things we knew or suspected from elsewhere.
The idea is that in spacetime foam, every point in spacetime has the huge amount of vacuum energythe lowest energy state equivalent to "empty space"predicted by quantum theory, but behaves differently to other points. For any particular way in which a point in spacetime is behaving, the exact opposite is equally as likely to occur at another point in spacetime. This is the feature of spacetime foam which cancels out the extra energy and expansions at a tiny scale, resulting in the lower energy that we observe at the scale of the whole universe.
For this to work, one has to assume that at the quantum level, time has no intrinsic "direction." In other words, there is no "arrow of time." According to Carlip, in the quantum world, this isn't such a wild suggestion. Most physicists would agree that we don't know at a fundamental level why there's an arrow of time at all, he said. The idea that it's somehow 'emergent' on larger scales has been around for a long time.
Carlip calls spacetime foam a complex microscopic structure." It can almost be thought of as an expanding universe formed by tiny expanding and contracting universes at every point in spacetime. Carlip believes its possible that over time, the expanding areas of spacetime each replicate the complicated structure, and are themselves filled with tiny universes at every point.
Another paper published in August 2019 explores this scenario more thoroughly. Authors Qingdi Wang and William G. Unruh at the University of British Columbia suggest that every point in spacetime cycles through expansion and contraction, like tiny versions of our universe. Every point in spacetime, they say, is a microcyclic universe, endlessly moving from singularity, to a Big Bang, and finally collapse, on repeat.
The tiniest computers in the universe and a theory of everything
Quantum foam is having something of a moment, not just as a solution to the Cosmological Constant Problem, but also to address other enigmas in physics, like black holes, quantum computers, and dark energy.
A forthcoming article by Ng suggests that spacetime foam holds the key to finally unify and explain phenomenon at both a quantum and cosmological scale, moving us towards the elusive Theory of Everything. Such a theory would explain areas of physics which are currently independent, and at times conflicting, under one coherent framework.
Like Carlip, Ng also derives the large value for a positive cosmological constant using a model of spacetime bubbles. But to do so, he treats the "bubbles" in quantum foam as the universes tiniest computers, encoding and processing information.
Remember: quantum foam contains bubbles of uncertainty in space and time. To measure how "bubbly" spacetime is, Ng suggests a thought experiment involving clocks clustered in a spherical volume of spacetime which transmit and receive light signals and measure the time it takes for the signals to be received.
This process of mapping the geometry is a sort of computation, in which distances are gauged by transmitting and processing information," he wrote in his paper.
Using other known relationships between energy and quantum computation, and the limit on mass inside the sphere to avoid forming a black hole, Ng argued that the uncertainty built into the quantum-scale universe that determines how accurately (or inaccurately) we can measure the geometry of spacetime also limits the maximum amount of information these bubble-computers can store and their computing power.
Extending this result for the entire universe rather than an isolated volume of spacetime, Ng shows that spacetime foam is equivalent to dark energy and dark matter, since ordinary matter would not be capable of storing and computing the maximum amount of information he derives from the measurement task.
The existence of spacetime foam, with the aid of thermodynamic considerations, appears to imply the co-existence of a dark sector (in addition to ordinary matter), Ng told Motherboard. This line of research is not common within the physics community, but it makes (physical) sense to me.
The key takeaway from Ng's work is is: not only can spacetime foam be measured and explored conceptually, but it can also explain the acceleration of the universe by connecting quantum physics, general relativity and dark energy. Ng believes a Theory of Everything is within reach.
Eventually what Id like to explore and, more importantly, what I would like to encourage others to explore, is to go beyond the consideration of spacetime foam, and to see whether both quantum mechanics and gravitation are emergent phenomena, and whether thermodynamics (whose protagonist is entropy) holds the key to understand the laws of nature," he said.
The future of foam research
Conceptually, spacetime foam reconciles and explains many of the outstanding problems between quantum physics and cosmology. Still, both Ng and Carlip are calling for more work to be done to truly understand the nature of spacetime.
Carlip is working on a quantitative model of spacetime foam to supplement the theoretical model currently on the table. Hes calling the model minisuperspace," and is hopeful that physicists researching other approaches in the quantum-cosmology intersection could find examples of the model in their own work, if they know to look for it. To start with, Carlip says hell be looking at some numerical simulations to support the foam model.
Going beyond a simple quantitative model will need an all hands on deck approach. I'd love to have people who are working on various approaches to quantum gravity, string theory, loop quantum gravity, asymptotic safety, etc., look for this kind of phenomenon in their work to see if a connection can be made, Carlip said.
Ng echoed the desire for more dedicated research which spans boundaries between different areas of theoretical physics. But his hope is even grander: for a unified theory which ties together quantum mechanics, gravity, and thermodynamics to explain the universe's mysteries.
Posted: at 11:29 am
Quantum computers may be closer to reality thanks to a discovery by researchers from John Hopkins University. Their recent paper, published in Science, describes their find of a superconducting material that can be the basis of the computers of the future.
The big difference between our contemporary computers and quantum computers is that instead of using bits of either "0" or "1" to store a piece of information, the quantum computers will employ quantum mechanics. They will store data in quantum bits (known as "qubits"). Such qubits exist in a superposition of two states, where both zero and one can be represented at the same time.
This technology, supercharging computational speed, could make quantum computers immensely superior to current computers, especially in such fields as artificial intelligence, predicting weather, the stock market, developing cures for illnesses, military applications and others.
What the John Hopkins scientists found is a way to create a qubit from a ring made out of a superconducting material known as -Bi2Pd, which naturally exists in a quantum state. Usually you would need to add magnetic fields to achieve this effect, a fact that makes the "flux qubit" created from this substance a possible "game changer," said Chia-Ling Chien, Professor of Physics at The Johns Hopkins University and the paper's co-author.
In their study, the researchers observed that -Bi2Pd exists between two states, with the current able to simultaneously circulate both clockwise and counterclockwise through its ring.
The scientists are most excited about the practicality of utilizing such a material.
Quantum computing overview that includes main concepts, recent developments from IBM, Intel, Google, Microsoft, D-Wave, Rigetti and other pioneers.
Much more research lies ahead, however, before the era of quantum computers is upon us. Next for the researchers is looking for Majorana fermions within -Bi2Pd. Finding these theoretical particles is seen as an important milestone in quantum computing. What's significant is that they are anti-particles of themselves and can lead to error-free topological quantum computers.
The paper's first author. Yufan Li, a postdoctoral fellow in the Department of Physics & Astronomy at The Johns Hopkins University, thinks that discovering the special properties of -Bi2Pd bodes well for finding within it the fermions.
"Ultimately, the goal is to find and then manipulate Majorana fermions, which is key to achieving fault-tolerant quantum computing for truly unleashing the power of quantum mechanics," said Li in a press release.
Xiaoying Xu of Johns Hopkins University; and M.-H. Lee and M.-W. Chu of National Taiwan University were the additional co-authors of the paper.
Check out their new paper, published October 11th, in Science Magazine.
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Posted: at 11:29 am
Schrdingers cat can be both alive and dead so surely David Baddiel can be both a comedian and a playwright? When, in 2014, he launched his first solo comedy venture in 15 years, Fame: Not the Musical, he reports: I had a constant struggle. People were saying Im coming to your play, Ive heard great things about your play. Maybe it was because hed chosen a theatre venue (the Menier Chocolate Factory in London) to premiere the show, but I would constantly have to say, Its not a play its a one-man show. Baddiel is a comedian, to his fingertips. I found it threatening to my identity, he says now.
He pauses, draws breath, and then: But now I have written a play. Thats why were back at the Menier, where Gods Dice is being prepped for its stage debut. The show is the 55-year-olds first proper play: its not a one-man show, and hes not performing in it. The droll fiftysomething role has been offered to fellow standup Alan Davies, of Jonathan Creek fame now cast as a physics lecturer who co-authors a book with his Christian student, proving the Bibles miracles to be scientifically possible. For a religious readership, its manna from heaven. Henry is hailed as the new messiah to the chagrin of his Dawkins-alike celebrity atheist wife.
Baddiel is in the rehearsal room today, at the shoulder of director James Grieve, who is staging Henrys book launch, at which wife and student come to ideological blows. Afterwards, I ask Baddiel if he enjoys hearing his words brought to life. I find it difficult, he says, particularly with the comedy. Give a director a dramatic scene and they can direct it in 20 different ways that might all be equally valid. If you give them a reveal gag and they direct it wrongly, its like playing the wrong notes, and it wont get a laugh.
Baddiels prior experience of writing for others was on the musical then the movie The Infidel, to whose director, Josh Appignanesi, he made himself a fucking pain in the arse on set, demanding retakes when his gags werent delivered just right. The thing is, Baddiel explains and he has discussed this with his wife, and fellow comedy writer, Morwenna Banks it feels like youre getting cancer, like some terrible tumour is growing inside of you, when you see your lines being done wrong. Pause. I apologise to everyone who might be offended by that metaphor.
So hes on his best behaviour in rehearsals for Gods Dice, straining to trust Grieve (who is fucking brilliant) and keep his mouth shut. Not easy, of course, when jokes are your currency and when even the plays more substantial material is personal. Ive been reading a lot about physics, says Baddiel. I think its to do with my dad who worked as a research chemist for Unilever and brought up his family heavily under the influence of science. Baddiel pere, who now has dementia, formed 50% of the subject of My Family: Not the Sitcom, Baddiels tender and flabbergasting 2016 show about his parents and their eccentric relationships. Following on from Fame, it situated mid-career Baddiel in a creative purple patch, far removed from the laddish comedy for which, in the 90s, he made his name.
They say don't feed the trolls. But as a comedian, you dont ignore hecklers, you work with them
I think theres been a return of the repressed, or something, he says, because, in my 50s, Ive become obsessed with physics. Deeply submerged in that obsession, he noticed something. Essentially, quantum physics is a leap of faith. Its truths are not exactly unprovable but theyre certainly unseeable. You have to believe in them. So theres a parallel between believing in quantum physics and believing in God.
Baddiel began to wonder: what if a physicist experienced a crisis of the faith required to pursue his subject? Might one arrive at religious belief, not out of ignorance, but out of high intelligence? Behind that inquiry is Baddiels memories of his old mucker and Fantasy Football League sidekick Frank Skinner. Before I met Frank, he recalls, Id never met a very, very intelligent person who deeply believed in God, and that was really challenging to me as an atheist.
The plays other source was a Brian Cox lecture that Baddiel had attended, at which the physicist proposed the possibility of a diamond leaping by itself out of a velvet bag and reappearing elsewhere in the theatre. Admittedly, says Baddiel, it was a very unlikely possibility. But in a multi-world universe, it doesnt matter how unlikely something is. If its possible, it must be happening somewhere. And thats a miracle isnt it a diamond leaping suddenly out of a velvet bag? A scientifically possible miracle.
All of these revelations might challenge what Baddiel, who is culturally Jewish, describes as his fundamental atheism. Its a point of pride with him, certainly, that Gods Dice is not an atheist play. Believers have read it, scientists have read it (including the physicist Jim Al-Khalili), and everyone credits its open-mindedness on the overlaps between faith and science. Baddiel himself remains a sceptic, albeit one who admits the play is borne of a spiritual crisis of sorts. As I get older and nearer death, I really want to understand the world before I die. And I dont believe in God, so maybe this physics is the way to understand it.
But [theoretical physicist] Richard Feynman said, If you think you understand quantum mechanics, you dont understand quantum mechanics. And I dont understand it. Sometimes when I read these books, I feel like I understand it for a minute and then, Oh no, I dont understand it again. Intellectually, its very frustrating. There is consolation, though, in fashioning that near-miss incomprehension into stories which Baddiel now sees as his stock in trade. I genuinely do not recognise borders between different kinds of storytelling, says the novelist, screenwriter, and writer of hit childrens books. If youre good at storytelling, you should be able to apply the idea to whatever genre fits it best.
As if to prove the point, hes drafting a new standup show or at least as close as he gets to standup, now that theatrical one-man show is more his bag. Trolls: Not the Dolls will tour in 2020, and addresses Baddiels self-confessed dependence on social media. (I would say its got a bit out of hand for me) It was born of the moment when, faced with a dont feed the trolls campaign by fellow celebs, he thought: Thats not right for me. To me theyre hecklers. Theyre people calling me a cunt, or telling me Im shit. And as a comedian, you dont ignore hecklers, you work with them.
As his 624,000 Twitter followers will know, Baddiel devotes time to outsmarting his online tormentors. The new show will trace these relationships through his 10 years on the platform, and will ask: Why is everybody so angry? What is anger doing for people? Why is everything so polarised? Social media involves people not imagining how the other person feels while raging at them. So the battle is to restore empathy to this empathy-less world. But isnt it painful to walk towards all of this hostility? If someone slags me off on social media, says Baddiel, I definitely still feel a stab of hurt and vulnerability. And then I think: material!
Trolls will be, he says, his most political show, and one that stakes out the kinds of dark territory into which a prominent Jewish person online can easily be lured. Baddiel is also making a BBC documentary about Holocaust denial and conjuring with a second play, about #MeToo. He eye-rolls with trepidation at that possibility, mindful that not everyone wants to hear the well-off, middle-aged straight mans take on gender politics. But he resists the suggestion that comedy is under threat from a new censoriousness.
Unpleasant and awful things sometimes need to be said in comedy and how you get there is the art
Ive a problem with the polarisation of that conversation, says the man whose Radio 4 show Dont Make Me Laugh was cancelled after broadcasting a supposedly off-colour remark about the Queen. The idea that, Oh, were over here with the free speech and offensiveness, and youre over there with the woke comedy. I dont think it should be seen like that.
Baddiel chooses to stake out a space for independent thinking. More and more, I dont map any received political viewpoint on to what I say in my work. Id rather ask myself, What do I actually think about this thing? And he craves nuance. Unpleasant and awful things sometimes need to be said in comedy and how you get there is the art. Fewer people seem to be able to understand this, but someone can be a brilliant comedian and say stuff that is unacceptable. Those things are entirely compatible.
Its a quantum physics way of thinking from a comic committed to keeping contradictory possibilities alive. Comedy/theatre, science/religion, brilliant/unacceptable and emotional/meaningless. Something about religion will always be immensely powerful, aesthetically and emotionally, he says, while his new play comes to life in the room next door. But I do believe that life is meaningless finally. Its fucking brilliant. But then its gone and thats it.
Thats not a cheerless conclusion. I say, accept the meaninglessness and enjoy yourself in whatever way you can.
Read the rest here:
Quantum Physics Blows Us Away: Endless Worlds With Countless Versions Of You Could Really Be Out There – Dual Dove
Posted: at 11:29 am
The idea of multiple universes that contain more versions of ourselves has been out there for a really long time and it managed to give birth to countless movies and books as well.
But it seems that reality could be more powerful than fiction, as this idea may be true indeed, according to the latest reports coming from NBCNews.
This idea that there are countless versions of you which exist across lots and lots of worlds is definitely really far from our intuitive experience.
Countless versions of you across lots of worlds
It seems that according to a popular analysis of quantum mechanics which is known as the many worlds interpretation, every fundamental event that has multiple possible outcomes whether its a particle of light hitting Mars or a molecule in the flame bouncing off your teapot splits the world into alternate realities, according to the online pubcalition mentioned above.
The article continues and explains that even for experts its pretty strange to think that the universe can split apart and its reportedly even stranger to realize that such a similar splitting could be occurring for each and every interaction that is taking place in the quantum world.
Things get even odder when we think at the fact that all these subatomic splits would apply to bigger things as well which obviously include ourselves.
Its possible that there are many versions of you out there
Its absolutely possible that there are multiple worlds where you made different decisions. Were just obeying the laws of physics, according to Sean Carroll, a theoretical physicist at the California Institute of Technology.
Its interesting to note that he is also the author of a new book on many worlds titled Something Deeply Hidden.
He continued and said We dont know whether the number of worlds is finite or infinite, but its certainly a very large number, Carroll says. Theres no way its, like, five.
We recommend that you head over to the original article on NBCNews in order to find out more juicy details on this exciting subject.
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