Daily Archives: October 3, 2021

What happened

Shares of next-gen encryption-software trailblazer Arqit Quantum (NASDAQ:ARQQ) were up 10.9% as of market close today, according to data provided by S&P Global Market Intelligence. Arqit, which just went public via a SPAC merger at the start of September, is currently double the price it was when it made its publicly traded debut, but is half its peak valuation in mid-September. Suffice it to say, this has been a wild ride higher for shareholders who bought in early.

Arqit currently boasts a market cap of over $2.3 billion, a sizable valuation for a fresh software business like this. As the name implies, this stock is a bet on the nascent quantum-computing industry.

The mind-bending technology that taps quantum physics to accelerate computing speed still has a very long way to go before widespread commercialization. But quantum computing has made some strides this year. For example, IonQ is working to build a network of quantum computers and is about to merge with SPAC dMY Technology Group III (NYSE:DMYI). Honeywell (NYSE:HON) also recently announced it will spin off its Quantum Solutions segment and merge it with software company Cambridge Quantum Computing.

Image source: Getty Images.

We're still a long way from quantum computers disrupting the status quo in the tech industry, but if and when it does, these advanced computers could force a reworking of cybersecurity services. That's where Arqit's product comes in.

Arqit has developed what it calls the QuantumCloud encryption service, built to protect data and digital assets (including cryptocurrencies like Bitcoin and other blockchain-based assets) on the internet from the threat a quantum-based cyber attack might pose one day.

It's not just protection from a sci-fi-sounding future that has some investors excited about Arqit stock. The company says it's working with a few dozen multinational companies and government agencies, with $130 million in revenue under contract and an additional pipeline of $1.1 billion.

However, new SPAC IPOs like this sometimes get hot after going public, only to quickly come back down to reality. With minimal actual sales to speak of right now, Arqit Quantum's current valuation assumes its lofty projections over the coming years transpire.

Don't rush in on the hype. But if quantum computing interests you, this is a rare pure-play stock in this futuristic industry to keep tabs on.

This article represents the opinion of the writer, who may disagree with the official recommendation position of a Motley Fool premium advisory service. Were motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.

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Why Shares of Arqit Quantum Were Up Nearly 11% Today - The Motley Fool

Science fiction is a genre rich with wonderful stories, action-packed adventures, and worlds beyond our own. Everyone can agree that sci-fi stories are fictional, but they arent necessarily impossible. Their use of theoretical physics to explain tropes like time travel and hyperspace goes to show that attention is paid to real science while constructing these fantastical stories. The question is, how much of the science in sci-fi is real, and how much of it is the result of creative liberty?

Conquering time

The physics underlying time travel isnt always explicitly stated in the books, shows, or even novels that portray it; many of them just assume time travel is possible and get on with the story.

Take Doctor Who, where time travel is made possible through the TARDIS. The TARDIS, the infamous bigger-on-the-inside blue police box, is powered by whats called the Eye of Harmony, a star that is forever collapsing into a black hole and can travel anywhere in time and space. It navigates an extradimensional tunnel known as the Time Vortex, travelling between different points in time and space in much the same way that hyperspace in Star Wars allows for travel between different points in the Galactic Empire.

Despite being fictional, Doctor Who has had an impact on actual physicists time travel theories. Physicists Benjamin K. Tippet and David Tsang have written a paper explaining how a mechanism like the TARDIS might be able to travel through time.

Their paper calls upon Einsteins theory of general relativity, which states that time and space are combined to make up a four-dimensional spacetime. Tippet and Tsang propose the creation of a bubble of spacetime that could travel freely backwards and forwards through time. Although such a bubble would violate certain universal laws of physics, Tippet and Tsang helpfully suggest a hypothetical kind of matter that the bubble could be built from that just doesnt follow these rules.

Splice and combine enough of those bubbles together, and you could create a tunnel removed from the regular flow of time like the one found in most of Doctor Whos opening credits. Its not a theory well ever see tested, but it does demonstrate how theoretical physics can be mapped onto fictional scenarios.

Jumping through the multiverse

The show Loki employs the unique version of time travel found in the Marvel Cinematic Universe. Rather than employing the butterfly effect, where the time travellers actions in the past affect the present, or the loop effect, where the time traveller is already part of past events, time travel in Loki creates a branching timeline: the actions of time travellers in the past have no effect on their original timeline.

Lokis version of time travel does hold merit in the scientific community. A physics professor from the California Institute of Technology provided a similar explanation of time travel to the one Loki established, where a branching timeline is actually a branching universe. This concept of branching timelines ties into the many worlds theory of quantum mechanics.

While Loki and Doctor Who both employ a degree of actual science, they are also both based on the assumption that time travel is possible. They use time travel as a plot device, taking creative liberties to make it possible but when it comes to showing how it works, they try their hand at creating an explanation thats more scientific than magical.

Taking speed to the limit literally

Spaceships are a staple of science-fiction stories, and none more so than the ships in Star Wars and Star Trek. Almost everyone recognizes the names Millenium Falcon and USS Enterprise.

They each take their own approach to traversing galaxies. Star Treks warp speed precedes Star Wars hyperspace. It creates an engine known as the warp drive, which uses a reaction between matter and antimatter to reach and exceed the speed of light. Each speed increase is called a warp factor, and the engines go from warp factor one the speed of light to warp factor 10 infinite speed. Everything in between is a multiple of the speed of light.

The warp drive operates by pushing spaceships through a wormhole a part of space that has curved in on itself, connecting two different parts of the universe.

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Putting the 'sci' in sci-fi The Varsity - Varsity

image:Fig. 1. left: the polarization induced by the vortical flow; right: the polarization induced by the shear flow. Red and yellow arrows represent the spin and momentum directions, respectively. view more

Credit: Shuai Liu

Chinese researchers recently discovered a new effect that can generate spin-polarization in fluid. The new effect, which is called "shear-induced polarization (SIP)," predicts that shear flow can induce polarization in the momentum space.

This research was conducted by scientists from the Institute of Modern Physics (IMP) of the Chinese Academy of Sciences (CAS), together with their collaborators at Peking University and Central China Normal University, who studied polarization induced by shear flow for the first time. Their discoveries were published inPhysical Review LettersandJournal of High Energy Physics.

In flowing fluid, one may observe some special patterns of the flow field, such as those formed by the vortical flow, which rotates around a center and is related to the orbital angular momentum of the fluid. Due to spin-orbit coupling, the orbital angular momentum of the vortical flow can transfer to the spin of a particle. This vorticity-induced spin polarization hasbeen observed in a quantum fluid.

Besides vortical flow, shear flow is also quite common in fluids. However, it is far less intuitive how shear flow is related to angular momentum. Thus, how it affects spin polarization has never been investigated before.

In this research, using relativistic many-body quantum theory and linear response theory, the researchers systematically studied spin polarization in a hydrodynamic medium.They discovered that shear flow, although not intuitively related to orbital angular momentum, also generates spin polarization in the momentum space through spin-orbit coupling.

Employing a relativistic hydrodynamic model, the researchers then investigated how this new SIP effect manifests in relativistic heavy-ion collisions. Since previous studies do not include the SIP effect, their predictions always have the opposite sign compared to experimental observations. This discrepancy is sometimes called the "spin-sign puzzle"and has bothered the research community for several years.

However, once the SIP effect is included, the strange quark polarization predicted by the theory demonstrates a pattern similar to the measured Lambda polarization in experiments.

Considering the close relationship between strange quark polarization and Lambda polarization, thecurrent study is expected to be an essential step toward the final solution of the spin-sign puzzle.

This work was supported by the National Natural Science Foundation of China and the Strategic Priority Research Program of CAS.

Physical Review Letters

Experimental study

Not applicable

Shear-Induced Spin Polarization in Heavy-Ion Collisions

30-Sep-2021

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

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Scientists discover spin polarization induced by shear flow - EurekAlert

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Coming together in an improbable encounter are Georgie (Erika Schindele), an uninhibited American in her early 40s, and Alex (Paul Whitworth) a staid Irishman in his mid-70s.

They might as well be from two different planets, as we quickly discover at the tempestuous start of Heisenberg: The Uncertainty Principle, the vibrant opening production of the Jewel Theatres long overdue 2021 season. So randomly implausible is their meetingmuch less their ensuing entanglementthat they might as well be acting out a version of quantum physicist Werner Heisenbergs uncertainty principle.

In fact, they are. Playwright Simon Stephens argues that none of us can possibly know how or when random occurrences can alter our well-ordered world. Think of it as a high-concept variation of screwball comedy: a wacky woman pursues an inhibited man and overthrows his worldand hersin the process. Two radically unsuited people collide, clash, and invariably begin adjusting themselves until, well, I wont reveal the ending. Heisenberg flirts with that clich just enough to catch us off-guard, and then sets up a whiplash trajectory.

From the moment she encounters Alex, Georgie gushes, confesses, vacillates, and refuses to be pinned down. Written by the British Stephens as a stereotypically uninhibited American woman, Georgie swears constantly, gestures impulsively and changes moods pathologically. Im a waitress, no Im not, yes I am, she tells Alex. Heisenberg himself would smile at the very idea of us trying to predict the behavior of any human being. Certainly not Georgie, as finessed by an adroit and kinetic Schindele.

Just as we grow used to the idea that Georgie is a wildly dysfunctional but worldly character, the playwright reveals Alexs own eccentricities, and his sophistication about life, sex, love, and music. To hear Paul Whitworth enumerate the seemingly endless styles of music his character enjoysfrom rock n roll to classical to rap to dubstepis to be enchanted. By the end of the play, the colliding characters have almost exchanged places, each awakening to the random possibilities of an unpredictable world. Its hard to grasp that youre watching actors, rather than eavesdropping on two people transform impossibility into transformative grace.

Schindele brings aerobic energy to her role as a loose cannon in this artful and entertaining production. Her nonstop outpourings of half-truths and expletive-infused guesses ricochet against the bemused quirks of Paul Whitworths Alex. She might be nuts, he might be lonely. She might be missing a son, he might talk to his dead sister. Along with the audience, the two of them have to guess when and if the other is telling the truthor what that might even mean. The pace accelerates when Alex responds to Georgies abrupt sexual overtures. And some of the finest scenes between the two actors happen in the intimate moments they both relish in the plays center. We are as surprised as they are at their happy collision, however temporary it may be.

What a pleasure to see Paul Whitworth take the stage again. Just to hear his astonishing voice, grown lower in pitch over the years, is akin to inhaling a snifter of fine single malt. While his Irish accent occasionally wanders, his control of face and handsevery movementis rich with nuance. Whitworth has an uncanny ability to embody the act of listening; Ive never seen an actor do so with more ferocity, care and wit than he does in Heisenberg. The two actors work seamlessly together, speaking and moving continuously throughout the production. The satisfying and spare set design by Andrea Bechert becomes a train-station bench, a butcher counter, a restaurant table, a bed, and a desk. These appear and disappear through a few deft moves by the players.

Smart lighting design by Kent Dorsey and fine direction by Paul Mullins add to the lingering spell of Heisenberg, the start of a theater season weve missed for so long.

As the chaos of opposing paces and purposes begins to synchronize, the play heads toward into a surprise dance of closure. As in quantum physics, things arent where we look for them, and when we look too closely, they disappear. Applying this metaphor to the collisions of two unlikely people, Heisenberg reverberates long after the lights have come up.

Heisenberg: The Uncertainty Principle, starring Paul Whitworth and Erika Schindele, plays at the Jewel Theatre through October 10.

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Physics and comedy collide in Simon Stephens' play - Good Times Weekly

For many years, scientists have been trying to harness Bloch oscillations, an exotic kind of behavior by electrons that could introduce a new field of physics and important new technologies. Now, MIT physicists report on a new approach to achieving Bloch oscillations in recently introduced graphene superlattices. Graphene's electronic properties undergo an interesting transformation in the presence of an electric mesh (a periodic potential), resulting in new types of electron behavior not seen in pristine materials. In their recent work, the scientists show why graphene superlattices may be game changers in the pursuit of Bloch oscillations.

Normally, electrons exposed to a constant electric field accelerate in a straight line. However, Quantum Mechanics predicts that electrons in a crystal, or material composed of atoms arranged in an orderly fashion, can behave differently. Upon exposure to an electric field, they can oscillate in tiny wavesBloch oscillations. This surprising behavior is an iconic example of coherent dynamics in quantum many-body systems, says Leonid Levitov, an MIT professor of physics and leader of the current work. Levitov is also affiliated with MITs Materials Research Laboratory.

Importantly, Bloch oscillations occur at a frequency value that is the same for all electrons and is tunable by the applied electric field. Further, typical frequency valuesin the terahertz range, or trillions of cycles per secondare in the range that is difficult to access via conventional means. Todays electronics and optics work at frequencies below and above the terahertz, respectively. Terahertz frequencies are something in between, and were not benefiting from them as much as from the rest of the spectrum, Levitov says. If we could easily access them, there could be many applications, ranging from better non-invasive security scanning at airports to new electronics designs.

Bloch oscillations are very sensitive to scattering processes in the material due to lattice vibrations (phonons) and disorder. As a result, although earlier work aimed at creating Bloch oscillations was extremely importantone approach, relying on semiconducting superlattices, led to a Nobel Prize and modern-day solid-state lasersit met with only limited success toward its original goal. People did see signatures of Bloch oscillations in these systems, but not at the level that would be useful for anything practical. There was inevitably some dephasing, which turned out to be pretty damning [for the phenomenon], Levitov says.

However, a new material known as moir graphene may make all the difference. Pioneered at MIT by Physics Professor Pablo Jarillo-Herrero, moir graphene is composed of two sheets of atomically thin layers of graphene placed on top of each other and rotated at a slight angle. And according to theory, this material should be an ideal candidate for seeing Bloch oscillations, Levitov says. In the recent paper, he and colleagues analyzed the materials parameters that impact how electrons move in it and how little disorder it has, and we show that on all accounts, moir graphene is as good as the semiconducting superlattices, or better.

Furthermore, other appealing varieties of superlattices have appeared recently, involving graphene paired with hexagonal boron nitride, or with patterned dielectric superlattices. Among additional advantages, graphene superlattices are much easier to make than the complicated structures key to the earlier work. Those systems were produced by only a few highly qualified groups around the world, Levitov says. Moir graphene is already being made by several groups in the US alone, and many more worldwide.

Finally, Levitov and colleagues say, moir graphene meets another important criterion for making Bloch oscillations practical. While the electrons involved in the oscillations do so at the same terahertz frequency, without a little help theyll do so independently. The key is to coax them to oscillate in synchrony. If you can do that, then you go from essentially a one-electron phenomenon to macroscopic oscillations that will be easily detectable and very usable because they will become a source of macroscopic current, Levitov says. The scientists believe that the electrons in moir graphene should be quite amenable to synchronization using standard techniques.

Comments Dmitri Basov, Higgins Professor and Chair of Physics at Columbia University: Like many other predictions by Leonid Levitov and his team, this new result on Bloch oscillations will most certainly motivate numerous experimental studies. I predict it will not be easy to observe Bloch oscillations in moir flat band systems, but we will certainly try! Basov was not involved in the work reported in Physical Review Letters.

Levitov is excited about continuing the work, which will include MIT undergraduates. The best part of this will come later when we see experimental results that prove the idea, he says.

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Moir graphene may assist in harnessing Bloch oscillations | Graphene-Info - Graphene-Info

By now, just about everyone knows about black holes: the all-consuming regions in outer space that are so dense that not even light can escape from their mysterious interior. But those are only one kind of black hole, even if they are the most famous of the bunch.

There can be other kinds of black holes that trap other physical phenomena, like sound waves, and these kinds of black holes, known as sonic black holes, might be critical to understanding their light-consuming counterparts in the wider universe.

Most important of all, what can sonic black holes tell us about one of modern physics' most contentious debates, the so-called Information Paradox? A recent study attempted to find out, and its results seem to make the problem more complicated, not less.

One commonly-known understanding about black holes is that whatever falls into a black hole doesn't come back out, not even light. But in 1971, physicist Steven Hawking proposed an interesting theory, which set off a series of discussions that changed the way physicists looked at black holes. He predicted that the total area of a black holes event horizon would never decrease. This statement is similar to the second law of thermodynamics, which states that the entropy, or degree of disorder within an object, should also never decrease.

Hawking's theory suggested that black holes could behave as thermal, heat-emitting objects in contradiction to the normal understanding of black holes as objects which never let energy escape. In 1974, Hawking proposed a solution to this contradiction by showing that,over exceptionally long timescales, black holes could have both entropy and emit radiation by taking into account their quantum effects. This phenomenon was dubbed Hawking radiation.

Hawking argued that black holes were actually acting as an idealized black body in space that absorbed all wavelengths of light, but which emitted energy calledblack body radiation, orHawking radiation, all along the event horizon.

That is because of virtual particles matter and anti-matter particles that momentarily spawn in space out of nothing and due to their proximity to each other immediately annihilate each other and release the energy used to produce them in the first place. This maintains the vital law of thermodynamics that states that the energy of a closed system (the universe) must remain constant.

But, if a pair of virtual particles spawn along the edge of an event horizon, one of the two particles will get sucked into the black hole, while the remaining particle survives and flies away into space as a form of energy known as Hawking radiation.

You can see the problem, right? The universe just took some of its energy and created matter out of nothing, but didn't get that energy back.

The only way Hawking radiation could be allowed to exist mathematically is if the in-falling particle actually had negative energy equal in magnitude to the positive energy used to create the two particles, thereby preserving the universe's total energy.

This leads to another problem though, as that particle falling into the black hole is now a part of it, and so the negative energy balance of the particle is taken out of the energy of the black hole.

It might be slight, all things considered, but if a black hole doesn't accrete any additional material to itself, all of those infinitesimally small energy deductions will start reducing the black hole's mass. Given enough time, the black hole actually evaporates out of existence.

You might be asking why that's a problem after all, that's one less black hole to accidentally run into out there but the problem is that particles aren't just matter, they also carry quantum information, such as position, spin, and velocity.

Quantum mechanics as we know it requires that this information, just like the energy of the universe, must be preserved. It might be scrambled beyond all recognition, but there's nothing in physics that says you can't go back and undo that scrambling and reclaim that information unless it was either inside a black hole or encoded into its event horizon when that black hole winked out of existence, thus taking that information with it.

What happens to that quantum information is the heart of the Information Paradox, and physicists and philosophers have been trying to untangle it ever since to no avail.

To understand a sonic black hole, let's review the physics of a traditional black hole in space. Gravity is the warping in the fabric of spacetime that is caused by an object's mass. That warping can be envisioned as a sloped well with the object at the bottom, pulling down and stretching the fabric below the plane of unaffected space-time.

In order to climb out of that well, you need to reach a certain speed, known as escape velocity. So, in order to escape the gravity well of Earth, you need to travel about 6.95 miles per second (11.19 m/s), or a little over 25,020 mph (about 40,270 km/h). Anything less, and you'll fall back down to Earth eventually.

The only thing that makes black holes different in this sense is that a black hole's escape velocity exceeds the speed of light. So, like a rocket that is only going 6.8 miles per second, light can get very high up the slope of a relatively small black hole's gravity well, but just not enough to get fully out of it.

In effect, the light would enter into a decaying orbit as it slowly spirals back down the center, like a bit of dirt caught in the whirlpool at the bottom of a drain in a bathtub. The more massive the black hole, the higher the slope of that well, so that light might barely be able to climb it at all.

A sonic black hole then, is this exact same phenomenon, except where the escape velocity of an object exceeds the speed of sound, rather than the speed of light. Fortunately, the speed of sound is much, much lower than the speed of light, so at sea level with a temperature of 59 degrees Fahrenheit (15 degrees Celsius), sound travels at 761 miles per hour (about 1224.74 km/h).

All an object (at sea level and at 59 degrees Fahrenheit) would needis an escape velocity infinitesimally greater than 761 miles per hour and it could prevent sound from escaping its event horizon, just as sure as its space-dwelling counterparts trap light.

Since sonic black holes and light black holes both have this basic property around their escape velocities, there is a lot of interest around whether we can use sonic black holes to effectively model the light-consuming black holes we find in space.

This is especially important since it's impossible to actually measure Hawking radiation, since we'd be talking about individual photons appearing just outside an event horizon. These would be too faint to ever detect without, say,surrounding a black hole in a super-cold Dyson Sphere-like detector that blocks out any outside radiation and which emits less energy than the black hole does itself.

So, the only way to really test for Hawking radiation is to find analogies that we can actually create and measure, which is where sonic black holes come in. Since a sonic black hole with its own event horizon for sound energy is something that we can create in a lab, can it give us insight into Hawking radiation?

A key feature of these sonic black holes is that they are just as immersed in the quantum field of the universe as a supermassive black hole at the center of a galaxy, so virtual particles will be constantly popping in and out of existence throughout, including phonons, which are quantum units of sound equivalent to light's photons.

An Israeli research team created one such sonic black hole using about 8,000rubidium atoms cooled to nearly absolute zero and trapped in place with a laser beam to create aBose-Einstein Condensate (BEC), in which atoms become so densely packed they behave like one super atom.

The team then used a second laser beam to create an effectiveevent horizon, where one half of the BEC was flowing faster than thespeed of sound, while the other half moved slower.

What the team from Technion in Haifa, Israel, led by Jeff Steinhauer, found is that pairs of phonons (quantum sound waves) did in fact appear on either side of the sonic event horizon, with the pair in the slower half getting swept away from the "event horizon" andthe phonon on the faster half became trapped by the speed of the supersonic flowing BEC, just as Hawking predicted a photon would from the event horizon of a black hole in space.

In a study the team published in January 2021 in the journal Nature, the team reported that theyobserved spontaneous Hawking radiation at six different times after the formation of the sonic black hole, and verified that the temperature and strength of the radiation remained constant. The evolution of the Hawking radiation throughout the life of the sonic black hole also compared to thepredictions for real black holes.The experiment provided experimental support to Hawkings analysis.

However, an inner horizon formed within the sonic black hole, in which the sound waves are no longer trapped. This inner horizon stimulated additional Hawking radiation, beyond the spontaneous emission.This phenomenon was not included in Hawkings analysis.

Not everyone is convinced that the two types of black holes are truly analogous, however.

A key point of contention is that Hawking speculates that all along the event horizon of a black hole, spacetime can be considered smooth; this is essential for the creation of Hawking radiation.

If spacetime around the event horizon is not smooth, however, quantum-scale variations could be encoding information into Hawking radiation in ways we can't detect.

What's more, the fact that sonic black holes and the Hawking radiation they produce behave a certain way does not prove that the light-trapping black holes in space that they are attempting to model will also behave in the same fashion.

In the Steinhauer team's recent experiment, the sonic black hole collapsedevery time they took a picture, due to the heat created in the process (the team repeated their experiment 97,000 times over 124 days to come up with the results in their paper). Therubidium atoms didn't disappear in the collapse, though; they remained, as did whatever quantum information the infalling phonon imprinted on them. This information can still, theoretically, be extracted even now.

What's more, even though a sonic black hole behaves the same way in one regard, the creation of an event horizon that produces a form of Hawking radiation, it might be too reductive to say that sharing a surface-level characteristic makes the two identical on more fundamental levels. A collection of 8,000 rubidium atoms in a BEC is not the same thing as a spacetime singularity of infinite density where physics as we know it breaks down. An analogy is just an analogy, after all.

Still, this recent experiment does provide some evidence that information that falls into a black hole is permanently lost when the black hole evaporates from Hawking radiation, so that raises the question of what would happen if this fundamental premise of quantum mechanics turned out to be incorrect?

A key principle of classical physics is that having a perfect knowledge of the state of all the particles of the universe should give you the ability to predict the future state of the universe at any given point in the future (at least theoretically).

Physics does not require that having such perfect knowledge of a current state gives you that same predictive ability about the past. If two different states (A and B) both lead to the same state (C), then you can know that having A and B will give you C and C, but having C by itself can't tell you whether you started with A, with B, or with both. That quantum information would be lost forever when A and B make the transition to state C.

Quantum mechanics forbids this loss of information, however, owing to the principle of unitarity, which essentially means that all probabilities of any given quantum state must sum to 1.

If we look at a six-sided die, the probability of getting a value between 1 and 6, inclusive, are all 1/6. But the probability of getting anyvalue is 1, which is the sum of all six probabilities of 1/6.

A six-sided die can't also become a five-sided die simply because it is rolled, all six sides of the die must remain intact during the transition between quantum states, so that two quantum states cannot become the same quantum state, they must remain separate and distinct.

Losing quantum information then is like taking one of those probabilities off the board, so rather than adding six values of 1/6 together, you add five of them and end up with 5/6 rather than 1. If this were possible, thenthe Schrodinger equation is wrong, the wave function is wrong, essentially the entire foundation of quantum mechanics is a lie and nothing is as it appears to be, even if a century of work in quantum mechanics tells us otherwise.

This is why the Information Paradox is such a thorny problem, since even though something as simple as permanently losing the knowledge of the spin of a virtual particle as it falls into a black hole might not seem like it should matter, it alters and unbalances the probabilities of the universe that quantum mechanics relies on, turning it from science to just really good guessing, and no one likes being told that they're just making stuff up.

There have been all sorts of proposed solutions to the information paradox over the years, and none have really settled the issue. Sonic black holes aren't likely to do so either, though they're still a pretty cool attempt regardless.

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What Sonic Black Holes Can Teach Us About the Information Paradox - Interesting Engineering

Rice physicists teamed with colleagues at Europes Large Hadron Collider to study matter-generating collisions of light. Researchers showed the departure angle of debris from the smashups is subtly distorted by quantum interference patterns in the light prior to impact. Credit: Illustration by 123rf.com

Understanding photon collisions could aid search for physics beyond the Standard Model.

Hot on the heels of proving an 87-year-old prediction that matter can be generated directly from light, Rice University physicists and their colleagues have detailed how that process may impact future studies of primordial plasma and physics beyond the Standard Model.

We are essentially looking at collisions of light, said Wei Li, an associate professor of physics and astronomy at Rice and co-author of the study published in Physical Review Letters.

We know from Einstein that energy can be converted into mass, said Li, a particle physicist who collaborates with hundreds of colleagues on experiments at high-energy particle accelerators like the European Organization for Nuclear Researchs Large Hadron Collider (LHC) and Brookhaven National Laboratorys Relativistic Heavy Ion Collider (RHIC).

Accelerators like RHIC and LHC routinely turn energy into matter by accelerating pieces of atoms near the speed of light and smashing them into one another. The 2012 discovery of the Higgs particle at the LHC is a notable example. At the time, the Higgs was the final unobserved particle in the Standard Model, a theory that describes the fundamental forces and building blocks of atoms.

Rice physics professor Wei Li (left) and postdoctoral research associate Shuai Yang teamed with colleagues at the Large Hadron Colliders (LHC) Compact Muon Solenoid experiment to study matter-generating collisions of light that occurred in heavy ion experiments at LHC. Yang lead-authored a newly published study that detailed how the departure angle of debris from the smashups is subtly distorted by quantum interference patterns prior to impact. Credit: Photo by Jeff Fitlow

Impressive as it is, physicists know the Standard Model explains only about 4% of the matter and energy in the universe. Li said this weeks study, which was lead-authored by Rice postdoctoral researcher Shuai Yang, has implications for the search for physics beyond the Standard Model.

There are papers predicting that you can create new particles from these ion collisions, that we have such a high density of photons in these collisions that these photon-photon interactions can create new physics beyond in the Standard Model, Li said.

Yang said, To look for new physics, one must understand Standard Model processes very precisely. The effect that weve seen here has not been previously considered when people have suggested using photon-photon interactions to look for new physics. And its extremely important to take that into account.

The effect Yang and colleagues detailed occurs when physicists accelerate opposing beams of heavy ions in opposite directions and point the beams at one another. The ions are nuclei of massive elements like gold or lead, and ion accelerators are particularly useful for studying the strong force, which binds fundamental building blocks called quarks in the neutrons and protons of atomic nuclei. Physicists have used heavy ion collisions to overcome those interactions and observe both quarks and gluons, the particles quarks exchange when they interact via the strong force.

But nuclei arent the only things that collide in heavy ion accelerators. Ion beams also produce electric and magnetic fields that shroud each nuclei in the beam with its own cloud of light. These clouds move with the nuclei, and when clouds from opposing beams meet, individual particles of light called photons can meet head-on.

In a PRL study published in July, Yang and colleagues used data from RHIC to show photon-photon collisions produce matter from pure energy. In the experiments, the light smashups occurred along with nuclei collisions that created a primordial soup called quark-gluon plasma, or QGP.

At RHIC, you can have the photon-photon collision create its mass at the same time as the formation of quark-gluon plasma, Yang said. So, youre creating this new mass inside the quark-gluon plasma.

Yangs Ph.D. thesis work on the RHIC data published in PRL in 2018 suggested photon collisions might be affecting the plasma in a slight but measurable way. Li said this was both intriguing and surprising, because the photon collisions are an electromagnetic phenomena, and quark-gluon plasmas are dominated by the strong force, which is far more powerful than the electromagnetic force.

To interact strongly with quark-gluon plasma, only having electric charge is not enough, Li said. You dont expect it to interact very strongly with quark-gluon plasma.

He said a variety of theories were offered to explain Yangs unexpected findings.

One proposed explanation is that the photon-photon interaction will look different not because of quark-gluon plasma, but because the two ions just get closer to each other, Li said. Its related to quantum effects and how the photons interact with each other.

If quantum effects had caused the anomalies, Yang surmised, they could create detectable interference patterns when ions narrowly missed one another but photons from their respective light clouds collided.

So the two ions, they do not strike each other directly, Yang said. They actually pass by. Its called an ultraperipheral collision, because the photons collide but the ions dont hit each other.

The Compact Muon Solenoid experiment at the European Organization for Nuclear Researchs Large Hadron Collider. Credit: CERN

Theory suggested quantum interference patterns from ultraperipheral photon-photon collisions should vary in direct proportion to the distance between the passing ions. Using data from the LHCs Compact Muon Solenoid (CMS) experiment, Yang, Li and colleagues found they could determine this distance, or impact parameter, by measuring something wholly different.

The two ions, as they get closer, theres a higher probability the ion can get excited and start to emit neutrons, which go straight down the beam line, Li said. We have a detector for this at CMS.

Each ultraperipheral photon-photon collision produces a pair of particles called muons that typically fly from the collision in opposite directions. As predicted by theory, Yang, Li and colleagues found that quantum interference distorted the departure angle of the muons. And the shorter the distance between the near-miss ions, the greater the distortion.

Li said the effect arises from the motion of the colliding photons. Although each is moving in the direction of the beam with its host ion, photons can also move away from their hosts.

The photons have motion in the perpendicular direction, too, he said. And it turns out, exactly, that that perpendicular motion gets stronger as the impact parameter gets smaller and smaller.

This makes it appear like somethings modifying the muons, Li said. It looks like one is going at a different angle from the other, but its really not. Its an artifact of the way the photons motion was changing, perpendicular to the beam direction, before the collision that made the muons.

Yang said the study explains most of the anomalies he previously identified. Meanwhile, the study established a novel experimental tool for controlling the impact parameter of photon interactions that will have far-reaching impacts.

We can comfortably say that the majority came from this QED effect, he said. But that doesnt rule out that there are still effects that relate to the quark-gluon plasma. This work gives us a very precise baseline, but we need more precise data. We still have at least 15 years to gather QGP data at CMS, and the precision of the data will get higher and higher.

Reference: Observation of Forward Neutron Multiplicity Dependence of Dimuon Acoplanarity in Ultraperipheral Pb-Pb Collisions at sNN=5.02TeV by A.M. Sirunyan et al. (CMS Collaboration), 17 September 2021, Physical Review Letters.DOI: 10.1103/PhysRevLett.127.122001

LHC and CMS are supported by the European Organization for Nuclear Research, the Department of Energy, the National Science Foundation and scientific funding agencies in Austria, Belgium, Brazil, Bulgaria, China, Colombia, Croatia, Cyprus, Ecuador, Estonia, Finland, France, Germany, Greece, Hungary, India, Iran, Ireland, Italy, South Korea, Latvia, Lithuania, Malaysia, Mexico, Montenegro, New Zealand, Pakistan, Poland, Portugal, Russia, Serbia, Spain, Sri Lanka, Switzerland, Taiwan, Thailand, Turkey, Ukraine and the United Kingdom.

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Physicists Probe Light Smashups To Guide Future Research Beyond the Standard Model - SciTechDaily

One of the most compelling ideas in all of physics sounds like pure fiction, but it could actually describe our reality: the idea of a multiverse. In the multiverse scenario, what we know as our universe is just one of many universes that independently and simultaneously exist in parallel to our own. Although there is no compelling evidence that points toward either the existence or nonexistence of the multiverse, it provides us with a rich area for exploration, because the predictions of its existence are firmly rooted in theoretical physics phenomena that are definitively known to exist.

If we presume that:

Then it follows that the existence of a multiverse is all but inevitable. It opens up a rich realm of physical possibilities that include not only parallel universes, but also an infinite number of them out there. If thats the case, there could even be parallel universes identical to our own, where reality forks each time a quantum outcome occurs. Heres whats possible within a scientific consideration of the multiverse.

To understand why physicists assert that a multiverse ought to exist, you first have to understand a few facts about the universe that we observe. One fact is that we have a boundary to the part of the universe that we can access: a boundary in time. The universe as we can see it began some ~13.8 billion years ago in an event known as the hot Big Bang, where the universe was hot, dense, filled with matter and radiation, and was expanding, cooling, and gravitating from that initial state. The farther we look back in space, the farther we wind up looking back in time, all the way to the boundary of the hot Big Bang: 13.8 billion years ago in time and 46.1 billion light-years away in space.

However, you cant go back to arbitrarily early times, because if the universe had exceeded a certain temperature and density, it would have properties we specifically observe it not to have. Instead, observations are far more consistent with the notion that the hot Big Bang was preceded and set up by a period of cosmic inflation, which:

When inflation comes to an end, we get a hot Big Bang with the necessary properties to reproduce the observable universe.

Typically, we like to visualize inflation as a simple field: it has certain properties that affect the space over which the field is present. As long as the field remains in this inflationary state, where the fabric of space has a large energy inherent to it, space will expand relentlessly and exponentially, so that the distance between any two points successively doubles with each passing interval of time.

As long as the field remains in this inflationary state, inflation continues, stretching the fabric of space, diluting everything in it until the field decays. At that moment, inflation ends. As the energy gets converted into matter and radiation, the universe heats up to a very high (but not arbitrarily high) temperature, signifying the beginning of the hot Big Bang.

In actuality, however, we know that whatever field drives inflation is overwhelmingly likely to be quantum in nature. That means, as inflation goes on, theres a certain probability that the field will: roll into the valley where inflation ends; a certain probability that it wont and inflation will continue; and even a certain probability that the field will roll in the wrong direction, taking us farther away from inflations end. And heres the counterintuitive part because the inflating universe continuously creates new space, all of these possibilities can occur simultaneously in different regions of the inflating universe.

This sets up a fascinating scenario to consider. As long as inflation occurred in the past, which we have copious evidence that it did based on whats imprinted in our universe, it implies the existence of a multiverse. Whats going on is the following:

And so on.

Fascinatingly, its fairly easy to show that if you want to create a scenario where we get enough inflation to set up the hot Big Bang with the properties we observe, you will always get a multiverse one where independent, disconnected universes are always being born, forever separated from one another by space that continues to inflate eternally, while new universes and new hot Big Bangs continue to spawn. As long as weve got this part of the story correct and the evidence overwhelmingly indicates that we have the existence of a multiverse is predicted by todays best science.

Now, this is where we have to enter into speculative territory. We know that inflation must occur at an energy scale thats significantly below the Planck energy scale, otherwise we would see signals in our universe that dont exist. What we dont know, however, is supremely important. We dont know how inflation began, or whether it even had a beginning; its possible that inflation was the default state of the universe that was happening eternally, until it ended in our region of space and our universe was spawned.

We dont know whether there are any entangled properties between these different universes within the multiverse. We dont know whether all of the universes that are spawned have the same physical laws and fundamental constants, or whether there are dynamics that govern these laws and constants that somehow get set either during inflation or the final transition to the hot Big Bang. Additionally, we have no idea how to quantify the probabilities of these different outcomes: what cosmologists working on it call the measure problem. These universes are predicted to exist, but we dont know how many of them there are, whether or how theyre related, and what similarities or differences they have relative to our own universe.

However, the expectation based on what we can measure within our own universe and what we can calculate based on the quantum properties that the known particles and fields possess is that the laws and constants should be the same between universes, but the specific initial conditions should be different.

What does this mean?

It means that the overall properties of each universe should be the same, because they had a common origin: from the end of the same inflationary field. That means each universe should be born with the same average energy density, the same laws, the same symmetries, the same conserved quantities and conservation laws, the same Standard Model, the same rules of general relativity, and many other properties. The big differences, simply, should come in the form of quantum fluctuations that get superimposed atop this uniform background: the 1-part-in-30,000 imperfections that provided the seeds of cosmic structure in our universe. These should be random and on all scales, and our universe should be just one of an extraordinarily large set of possible outcomes.

And yet, if you have enough of these universes that spring into existence, there should eventually be one that comes along with the exact same initial properties as our own. Remember that everything that exists in our universe is finite: there are a finite number of particles, a finite amount of energy, a finite amount of time over which interactions between quanta can occur, and a finite number of possible outcomes. These numbers are astronomically large, but they are not infinite.

It may or may not be the same story when it comes to the number of universes that are spawned by inflation. If inflation has proceeded for a finite amount of time, then the number of universes we get increases exponentially with time, but always remains finite. If inflation has gone on for an infinite amount of time, then the number of universes must be infinite, and all allowable possibilities must have occurred in some universe.

If inflation has gone on for only a finite amount of time, we can strongly say that, based on how the number of universes increases with time versus how the number of possible outcomes within a single universe increases with time, there are no parallel universes equivalent to our own within the multiverse. When we talk about the many-worlds interpretation of quantum mechanics, a finite number of universes is insufficient to hold all of the possible outcomes. We require an infinity of worlds. This itself requires an infinite duration to inflation to make a parallel universe identical to our own a possibility.

But if inflation has gone on for an infinite amount of time, then the existence of identical parallel universes isnt just possible, but mandatory. No matter how large a finite number gets, even if it tends towards infinity over time, it will never become infinite after a finite amount of time.

Therefore, even though there are an astronomical number of possible outcomes that could have occurred including quantum interactions with a continuous set of allowable outcomes an infinite number of parallel universes must contain them all.

However, even if such parallel universes do exist within a larger multiverse, even if there are an infinite number of them, not every imaginable effect is possible. You cannot transfer anything between universes, for example. Even though every universe emerged from the same small region of space seeing as you can trace any two points back in an inflating spacetime until theyre arbitrarily close together no information can ever be transferred between them; they are no longer causally connected.

There is no retrocausality that occurs. In other words, what happens in one universe cannot affect another. We know how to quantify what would occur, during inflation, if any two universes collided, merged, or otherwise interacted, and we can definitively state that there is no such evidence of that having occurred in our universe.

Additionally, the quantum possibilities that now exist for our universe are only possible for future events whose outcomes have already been determined. The idea that multiple histories could overlap to create the reality we now inhabit often colloquially known as the Mandela effect is a physically inadmissible example of pseudoscience, unsupported by any evidence at all.

Its extraordinarily tempting to consider the possibility that all of our mistakes and bad decisions, and the consequences that have ensued for ourselves and others because of them, might have turned out differently elsewhere. At another time in another place, perhaps there was a version of you that made better decisions at a critical juncture, and that version of you, in another universe, is having a better life and inhabiting a better world because of it. The idea of the multiverse, and specifically of parallel universes that were identical to our own until those critical decisions, offers us the hope that our past decisions are not as immutable as we currently believe.

And yet, thats not at all what the science indicates. Even if inflation has been ongoing for an infinite amount of time, whatever occurs in the other universes that exist are in no way related to what is occurring or has occurred in our universe. Our past is fundamentally written. There are no opportunities arising in any multiverse scenario either to rewrite the past or to import, from another universe, an outcome that turned out differently. The multiverse may be inevitable and parallel universes may be possible, but they do not affect our universe is any measurable or observable way. Beyond the limits of science, all we have is speculation. Until the evidence catches up, no further definitive statements can be made.

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Could the multiverse have parallel universes identical to ours? - Big Think