Category Archives: Quantum Physics
Measuring reality really does affect what you observe – Big Think
When we divide up matter into the smallest possible chunks that its made ofinto the stuff that can be divided or split no furtherthose indivisible things we arrive at are known as fundamental particles: the quanta that compose our Universe. But its a complicated story each time we ask the question: how does each individual quantum behave? Do they behave like particles? Or do they behave like waves?
The most puzzling fact about quantum mechanics is that the answer you get depends on how you look at the individual quanta that are part of the experiment. If you make certain classes of measurements and observations, they behave like particles; if you make other choices, they behave like waves. Whether and how you observe your own experiment really does change the outcome, and the double-slit experiment is the perfect way to show how.
This diagram, dating back to Thomas Youngs work in the early 1800s, is one of the oldest pictures that demonstrate both constructive and destructive interference as arising from wave sources originating at two points: A and B. This is a physically identical setup to a double slit experiment, even though it applies just as well to water waves propagated through a tank.
More than 200 years ago, the first double-slit experiment was performed by Thomas Young, who was investigating whether light behaved as a wave or a particle. Newton had famously claimed that it must be a particle, or corpuscle, and was able to explain a number of phenomena with this idea. Reflection, transmission, refraction, and any ray-based optical phenomena were perfectly consistent with Newtons view of how light should behave.
But other phenomena seemed to need waves to explain them: interference and diffraction in particular. When you passed light through a double slit, it behaved just the same way that water waves do, producing that familiar interference pattern. The light-and-dark spots that appeared on the screen behind the slit corresponded to constructive-and-destructive interference, indicating thatat least under the right circumstanceslight behaves as a wave does.
If you have two slits very close to one another, it stands to reason that any individual quantum of energy will go through either one slit or the other. Like many others, you might think that the reason light produces this interference pattern is because you have lots of different quanta of lightphotonsall going through the various slits together, and interfering with one another.
So you take a different set of quantum objects, like electrons, and fire them at the double slit. Sure, you get an interference pattern, but now you come up with a brilliant tweak: you fire the electrons one-at-a-time through the slits. With each new electron, you record a new data point for where it landed. After thousands upon thousands of electrons, you finally look at the pattern that emerges. And what do you see? Interference.
Electrons exhibit wave properties as well as particle properties, and can be used to construct images or probe particle sizes just as well as light can. Here, you can see the results of an experiment where electrons are fired one-at-a-time through a double-slit. Once enough electrons are fired, the interference pattern can clearly be seen.
Somehow, each electron must be interfering with itself, acting fundamentally like a wave.
For many decades, physicists have puzzled and argued over what this means must really be going on. Is the electron going through both slits at once, interfering with itself somehow? This seems counterintuitive and physically impossible, but we have a way to tell whether this is true or not: we can measure it.
So we set up the same experiment, but this time, we have a little light we shine across each of the two slits. When the electron goes through, the light is slightly perturbed, so we can flag which one of the two slits it passed through. With each electron that goes through, we get a signal coming from one of the two slits. At last, each electron has been counted, and we know which slit every one went through. And now, at the end, when we look at our screen, this is what we see.
If you measure which slit an electron goes through when performing a one-at-a-time double slit experiment, you dont get an interference pattern on the screen behind it. Instead, the electrons behave not as waves, but as classical particles. A similar effect can be seen for single-slit (at left) experiments as well.
That interference pattern? Its gone. Instead, its replaced by just two piles of electrons: the paths youd expect each electron to take if there were no interference at all.
Whats going on here? Its as though the electrons know whether youre watching them or not. The very act of observing this setupof asking which slit did each electron pass through?changes the outcome of the experiment.
If you measure which slit the quantum passes through, it behaves as though it passes through one and only one slit: it acts like a classical particle. If you dont measure which slit the quantum passes through, it behaves as a wave, acting like it passed through both slits simultaneously and producing an interference pattern.
Whats actually going on here? To find out, we have to perform more experiments.
By setting up a movable mask, you can choose to either block one or both slits for the double slit experiment, seeing what the outcomes are and how they change with the motion of the mask.
One experiment you can set up is to put a movable mask in front of both slits, while still firing electrons through them one-at-a-time. Practically,this has now been accomplishedin the following fashion:
How does the pattern change?
The results of the masked double-slit experiment. Note that when the first slit (P1), the second slit (P2), or both slits (P12) are open, the pattern you see is very different depending on whether one or two slits are available.
Exactly like you might expect:
Its as though if both paths are there as available options simultaneously, without restriction, you get interference and wave-like behavior. But if you only have one path available, or if either path is restricted somehow, you wont get interference and will get particle-like behavior.
So we go back to having both slits in the open position, and shining light across both of them as you pass electrons one-at-a-time through the double slits.
Double slit experiments performed with light produce interference patterns, as they would for any wave. The properties of different light colors is due to their differing wavelengths. The narrowly spaced bright-and-dark bands are the effect of the double slit; the more widely spaced dark and bright pattern is caused by the narrower single-slit effect. If you measure which slit the light (or any wave/particle quantum) passes through, this interference pattern gets destroyed.
If your light is both energetic (high energy per photon) and intense (a large number of total photons), you wont get an interference pattern at all. 100% of your electrons will be measured at the slits themselves, and youll get the results youd expect for classical particles alone.
But if you lower the energy-per-photon, youll discover that when you drop below a certain energy threshold, you dont interact with every electron. Some electrons will pass through the slits without registering which slit they went through, and youll start to get the interference pattern back as you lower your energy.
Same thing with intensity: as you lower it, the two pile pattern will slowly disappear, replaced with the interference pattern, while if you dial up the intensity, all traces of interference disappear.
And then, you get the brilliant idea to use photons to measure which slit each electron goes through, but to destroy that information before looking at the screen.
A quantum eraser experiment setup, where two entangled particles are separated and measured. No alterations of one particle at its destination affect the outcome of the other. You can combine principles like the quantum eraser with the double-slit experiment and see what happens if you keep or destroy, or look at or dont look at, the information you create by measuring what occurs at the slits themselves.
This last idea is known as aquantum eraser experiment, and it produces the fascinating result that if you destroy the information sufficiently, even after measuring which slit the particles went through, youll see an interference pattern on the screen.
Somehow, nature knows whether we have the information that marks which slit a quantum particle passed through. If the particle is marked in some fashion, you will not get an interference pattern when you look at the screen; if the particle is not marked (or was measured and then unmarked by destroying its information), you will get an interference pattern.
Weve even tried doing the experiment with quantum particles that have had their quantum state squeezed to be narrower than normal, and they not onlyexhibit this same quantum weirdness, but the interference pattern that comes outis also squeezed relative to the standard double slit pattern.
The results of unsqueezed (L, labeled CSS) versus squeezed (R, labeled squeezed CSS) quantum states. note the differences in the density-of-states plots, and that this translates into a physically squeezed double slit interference pattern.
It is extremely tempting, in light of all of this information, to ask what thousands upon thousands of scientists and physics students have asked upon learning it:what does it all mean about the nature of reality?
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Does it mean that nature is inherently non-deterministic?
Does it mean that what we keep or destroy today can affect the outcomes of events that should already be determined in the past?
That the observer plays a fundamental role in determining what is real?
A variety of quantum interpretations and their differing assignments of a variety of properties. Despite their differences, there are no experiments known that can tell these various interpretations apart from one another, although certain interpretations, like those with local, real, deterministic hidden variables, can be ruled out.
The answer, disconcertingly, is that we cannot conclude whether nature is deterministic or not, local or non-local, or whether the wavefunction is real. What the double slit experiment reveals is as complete a description of reality as youre ever going to get. To know the results of any experiment we can perform is as far as physics can take us. The rest is just an interpretation.
If your interpretation of quantum physics can successfully explain what the experiments reveal to us, it is valid; all the ones that cannot are invalid. Everything else is aesthetics, and while people are free to argue over their favorite interpretation, none can lay any more claim to being real than any other. But the heart of quantum physics can be found in these experimental results. We impose our preferences on the Universe at our own peril. The only path to understanding is to listen to what the Universe tells us about itself.
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Measuring reality really does affect what you observe - Big Think
Researchers reveal quantum interference in inter-layer Coulomb drag – Phys.org
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by University of Science and Technology of China
A team led by Prof. Zeng Changgan and Associate Researcher Li Lin from the University of Science and Technology (USTC) / Chinese Academy of Sciences (CAS) Key Laboratory of Strongly-Coupled Quantum Matter Physics, collaborating with Prof. Feng Ji's team from Peking University, revealed significant quantum interference effect in inter-layer transport process for the first time using graphene-based electronic double-layer systems. Their work was published in Nature Communications.
Coulomb drag is an effect that occurs between two conductive layers in proximity but insulated from each other, wherein moving carriers in one layer (active layer) induces the transport of carriers in the other layer (passive layer), thereby generating an open-circuit voltage in the passive layer.
Coulomb drag has been widely applied in previous studies of long-range interactions between carriers, such as the Bose-Einstein condensation of indirect excitons. However, there is a lack of research on the external field response and possible quantum effects of the Coulomb drag.
As a two-dimensional electron gas, graphene has highly adjustable carrier types and density, and using boron nitride (hBN) as an insulating layer, the distance between two layers of graphene can be reduced to a few nanometers, providing an ideal platform for studying the characteristics of inter-layer Coulomb drag.
On this account, the team constructed multiple graphene-based electronic double-layer systems such as double layers of bilayer graphene (BLG/BLG) with hBN as the insulating spacer, double layers of monolayer graphene (MLG/MLG) and MLG/BLG. By applying an external magnetic field on the graphene-based double-layer systems, the team observed that in a wide range of temperature and carrier density, the magneto-drag resistance deviates significantly from classical drag resistance in the low-field regime.
This low-field correction is sensitive to the band topology of the graphene layers. For example, a peak feature was observed in the low-field correction of BLG/BLG and MLG/MLG, while the BLG/MLG correction showed a valley feature.
By analyzing the transport process, the team found that the observed low-field correction can be well attributed to the quantum interference in the Coulomb drag between two layers that are interrelated by time reversal and mirror reflection. The emergence of such quantum interference relies on the formation of superimposing inter-layer diffusion paths, wherein the impurity potential scatterings from the intermediate insulating layer play a crucial role.
The discovery of this new quantum interference extended the quantum interference in solid materials from the single-particle transport process in single conductor to the multi-particle interactions between multiple conductors. Furthermore, compared with magnetoresistance correction in intralayer quantum interference, the magneto-drag resistance correction is significantly larger, providing a candidate for the future development of new-principle magnetic memory devices.
More information: Lijun Zhu et al, Signature of quantum interference effect in inter-layer Coulomb drag in graphene-based electronic double-layer systems, Nature Communications (2023). DOI: 10.1038/s41467-023-37197-2
Journal information: Nature Communications
Provided by University of Science and Technology of China
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Researchers reveal quantum interference in inter-layer Coulomb drag - Phys.org
The Electron Is So Round That Its Ruling Out New Particles – Quanta Magazine
Imagine an electron as a spherical cloud of negative charge. If that ball were ever so slightly less round, it could help explain fundamental gaps in our understanding of physics, including why the universe contains something rather than nothing.
Given the stakes, a small community of physicists has been doggedly hunting for any asymmetry in the shape of the electron for the past few decades. The experiments are now so sensitive that if an electron were the size of Earth, they could detect a bump on the North Pole the height of a single sugar molecule.
The latest results are in: The electron is rounder than that.
The updated measurement disappoints anyone hoping for signs of new physics. But it still helps theorists to constrain their models for what unknown particles and forces may be missing from the current picture.
Im sure its hard to be the experimentalist measuring zero all the time, [but] even a null result in this experiment is really valuable and really teaches us something, said Peter Graham, a theoretical physicist at Stanford University. The new study is a technological tour de force and also very important for new physics.
The Standard Model of Particle Physics is our best roster of all the particles that exist in the universes zoo. The theory has held up exceptionally well in experimental tests over the past few decades, but it leaves some serious elephants in the room, said Dmitry Budker, a physicist at the University of California, Berkeley.
For one thing, our mere existence is proof that the Standard Model is incomplete, since according to the theory, the Big Bang should have produced equal parts matter and antimatter that would have annihilated each other.
In 1967, the Soviet physicist Andrei Sakharov proposed a possible solution to this particular conundrum. He conjectured that there must be some microscopic process in nature that looks different in reverse; that way, matter could grow to dominate over antimatter. A few years before, physicists had discovered such a scenario in the decay of the kaon particle. But that alone wasnt enough to explain the asymmetry.
Ever since then, physicists have been on a hunt to find hints of new particles that could further tip the scale. Some do so directly, using the Large Hadron Collider often touted as the most complicated machine ever built. But over the past several decades, a comparatively low-budget alternative has emerged: looking at how hypothetical particles would alter properties of known particles. You see footprints [of new physics], but you dont actually see the thing that made them, said Michael Ramsey-Musolf, a theoretical physicist at the University of Massachusetts, Amherst.
One such potential footprint could appear in the roundness of the electron. Quantum mechanics dictates that inside the electrons cloud of negative charge, other particles are constantly flickering in and out of existence. The presence of certain virtual particles beyond the Standard Model the kind that could help explain the primordial supremacy of matter would make the electrons cloud look slightly more egg-shaped. One tip would have a bit more positive charge, the other a bit more negative, like the ends of a bar magnet. This charge separation is referred to as the electric dipole moment (EDM).
The Standard Model predicts a vanishingly tiny EDM for the electron nearly a million times smaller than what current techniques can probe. So if researchers were to detect an oblong shape using todays experiments, that would reveal definitive traces of new physics and point toward what the Standard Model might be missing.
To search for the electrons EDM, scientists look for a change in the particles spin, an intrinsic property that defines its orientation. The electrons spin can be readily rotated by magnetic fields, with its magnetic moment serving as a sort of handle. The goal of these tabletop experiments is to try to rotate the spin using electric fields instead, with the EDM as an electric handle.
If the electrons perfectly spherical, its got no handles to grab onto to exert a torque, said Amar Vutha, a physicist at the University of Toronto. But if theres a sizable EDM, the electric field will use it to tug on the electrons spin.
In 2011, researchers at Imperial College London showed that they could amplify this handle effect by anchoring the electron to a heavy molecule. Since then, two main teams have been leapfrogging one another every few years with increasingly precise measurements.
One experiment, now at Northwestern University, goes by the name of Advanced Cold Molecule Electron EDM, or ACME (a backronym inspired by the old Road Runner cartoons). Another is based at the University of Colorados JILA institute. The competing teams measurements have jumped in sensitivity by a factor of 200 in the last decade still with no EDM to be seen.
It is sort of a race, except we have no idea where the finish line is, or whether there is a finish line, even, said David DeMille, a physicist at the University of Chicago and one of the leaders of the ACME group.
To keep trekking ahead, researchers want two things: more measurements and a longer measurement time. The two teams take opposite approaches.
The ACME group, which set the previous record in 2018, prioritizes quantity of measurements. They shoot a beam of neutral molecules across the lab, probing tens of millions of them every second, but only for a few milliseconds each. The JILA group measures fewer molecules, but for longer: They trap a few hundred molecules at a time, then measure them for up to three seconds.
The ion-trapping technique, first developed by Eric Cornell, a physicist at the University of Colorado, Boulder who directs the JILA group, was a big conceptual breakthrough, DeMille said. Many people in the field thought this was nuts. Seeing it come to fruition is really exciting.
Having two distinct experimental setups that can cross-check one another is absolutely crucial, Budker said. I dont have words to express my admiration of this cleverness and persistence. Its just the best science there is.
Cornells technique was first showcased in 2017 with hafnium fluoride molecules. Since then, technical improvements have allowed the group to surpass ACMEs record by a factor of 2.4, as described in a recent preprint led by Cornells former graduate student Tanya Roussy. The team declined to comment while their paper is under review at Science.
Probing the electrons roundness with increased precision equates to looking for new physics at higher energy scales,or looking for signs of heavier particles. This new bound is sensitive to energies above roughly 1013 electron-volts more than an order of magnitude beyond what the LHC can currently test. A few decades ago, most theorists expected that hints of new particles would be discovered significantly below this scale. Each time the bar rises, some ideas are discredited.
We have to keep wrestling with what these limits imply, Ramsey-Musolf said. Nothings killed yet, but its turning up the heat.
Meanwhile, the electron EDM community forges ahead. In future experimental iterations, the dueling groups aim to meet somewhere in the middle: The JILA team plans to make a beam full of ions to increase their count, and the ACME team wants to extend the length of their beam to increase their measurement time. Vutha is even working on some totally crazy approaches, like freezing molecules in blocks of ice, in the hope of jumping several orders of magnitude in sensitivity.
The dream is that these EDM experiments will be the first to detect signs of new physics, prompting a wave of follow-up investigations from other precision measurement experiments and larger particle colliders.
The shape of the electron is something that teaches us about totally new and different pieces of the fundamental laws of nature, Graham said. Theres a huge discovery waiting to happen. Im optimistic that well get there.
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The Electron Is So Round That Its Ruling Out New Particles - Quanta Magazine
Lets take a quantum leap! – The New Indian Express
By Shrimansi Kaushik| Express News Service |Published: 11th April 2023 11:36 AMImage used for representational purposes only
HYDERABAD: Thinking of what will dominate the future of technology; scientists, academicians and entrepreneurs are increasingly looking at quantum mechanics. Quantum is being seen as the new-age paradigm of science, with the possibility of bringing a revolutionary change in how we perceive our physical world.To understand what possibilities quantum science brings, World Quantum Day is celebrated on April 14, a reference to the rounded digits of Plancks constant: 4.14 (4.1356676961015 eV.s), which essentially governs quantum physics.
Reiterating the amusing expression of Richard Feynman, I think I can safely say that nobody understands quantum mechanics, particle physicist Dr Bindu Bambah says that it is undoubtedly an unusual expression from the mouth of a physicist.
Explaining the mechanism that helped develop some of the crucial technologies today and why it is so revolutionary (and unusual), Dr Bambah says, In particular, in the quantum world, there are particles that behave like waves and waves behaving like particles, with consciousness and observers who create reality play a crucial role. Regardless of the details, everyone seems to agree that the world-view depicted by quantum theory is radically different from the one emerging from classical physics, because of this, many have identified the transition from classical to quantum mechanics as a prototypical example of a paradigm shift, such that the rise of quantum mechanics amounted to a scientific revolution, as famously described by Thomas Kuhn.
This explains all the infamous, yet plausible sci-fi movies are not all wrong when their storylines depict merging timelines. Dr Bambah explains what exactly is a paradigm shift. The transition from classical to quantum mechanics is an example of a Kuhnian scientific revolution, in which there is a shift from the simple, intuitive, straightforward classical paradigm, to the quantum, convoluted, counterintuitive, amazing new quantum paradigm.
Essentially it means to encounter a new understanding of what we have known so far, owing to an obstacle or a hurdle, but the shift would come when this novelty is assimilated into the known such that it becomes expected. Not every new thing, though, brings a paradigm shift.
Quantum emerged when several attempts to use the laws of classical physics failed to explain the behaviour of matter on the atomic scale. Quantum physics includes both the ideas of dealing with smallest units as well as biggest leaps. Quantum mechanics is the part that deals with the smallest elements.
It results in what may appear to be some very strange conclusions about the physical world. At the scale of atoms and electrons, many of the equations of classical mechanics, which describe how things move at everyday sizes and speeds, cease to be useful. In classical mechanics, objects exist in a specific place at a specific time. However, in quantum mechanics, objects instead exist in a haze of probability; they have a certain chance of being at point A, another chance of being at point B and so on, says Dr Bambah.
In 1918, the German physicist Max Planck got the Nobel in Physics for his discovery of the quantised nature of energy. Einstein proposed that quantization is a fundamental property of light and other electromagnetic radiation. This led to the concept of photons and further discoveries led to the concept of photoelectrons.
Scientists continued to dabble over the mysterious nature of matter, deliberating whether it is a wave or a particle, until Werner Heisenberg, with his uncertainty principle, explained that It is physically impossible to measure, simultaneously, the exact position and the exact momentum of a particle. The inescapable uncertainties do not arise from imperfections in practical measuring instruments but rather the quantum structure of matter, says Dr Bambah.
She says that quantum mechanics has evolved further and many new paradigm shifts have arisen, including the production of particles out of energy, giving rise to quantum field theory. Other is quantum entanglement and quantum information and of course, quantum computers. Each is a scientific revolution and we look forward to many more, she says.
To harness these new developments, the Indian government introduced a whopping 8000 crore in its 2020 budget for investment in quantum technology, she added. Two marvels of quantum mechanical thinking are lasers and quantum computers. Lasers work on the quantum mechanical process of stimulated emission of radiation giving intense monochromatic radiation used in eye treatments. Quantum computers promise to revolutionise computing as they offer more versatility for encoding information. Rather than the two-state binary encoding used in classical computers, the quantum mechanical principle of superposition allows multiple-state encryption, increasing the power of computing, said Dr Bambah.
In Hyderabad itself, said Dr Bambah, departments at academic institutes such as the University of Hyderabad, IIT and IIIT have made some remarkable contributions to the field of quantum physics.Shedding light on what quantum technology has in store for entrepreneurs, Nikhil Malhotra, Global Head, Makers Lab, Tech Mahindra said, I truly believe that the opportunities in the field are vast and there is plenty of room for innovation and growth. At Tech Mahindra, we have always been at the forefront of technological innovation & advancement and we are working to develop a quantum ecosystem to accelerate the adoption and commercialization of quantum technology globally. With quantum computing, our market can expand from $300 billion to $800 Billion by 2040.
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From GPS to Laser Pointers, Quantum Science Is All Around Us – NIST
NIST researcher Andrew Wilson holds a surface-electrode ion trap used for quantum information processing. The computer screen behind Wilson shows three white dots, a live microscope image of three single atoms. They are held in a triangle pattern by an ion trap like the one Wilson is holding.
Credit: R. Jacobson/NIST
If youve gotten around with GPS, had an MRI, or tormented your cat with a laser pointer, quantum science is a part of your life.
Ahead of World Quantum Day this week, we asked Andrew Wilson, who leads NISTs Quantum Physics Division, to explain just what exactly quantum science is and why it matters.
Well, it means different things to different people. But it essentially comes down to using fundamental quantum properties to do great things. When people talk about using quantum, it generally comes down to two things:
Entanglement and superposition are resources for quantum computing. These are what make quantum computing powerful.
I think in the early days of quantum physics, there were ideas like the laser. Quantum physics underpins the laser, and the laser turns out to be rather important. It supports the internet. Quantum also comes into things like MRI imaging and semiconductor chips. So, we rely on quantum behavior to understand how these things work. Thats quantum physics. This early version of quantum physics is called semiclassical physics. And a lot of technology based on this uses superposition. Today, this is widely referred to as Quantum 1.0.
But as we physicists kept working on quantum systems, and getting better at making and controlling these, we started thinking, OK, maybe we can do useful things with entanglement. So, we added entanglement to the toolbox. Thats Quantum 2.0. Quantum 2.0 is about trying to capture the advantages and the practical applications of both superposition and entanglement. Were really trying to see how we can make entanglement practical. There will have to be many scientific breakthroughs, including fundamental science, for this kind of technology to be ubiquitous in our economy and society.
At the same time that progress was being made in labs, some clever people realized that this toolbox could be used for information processing. Quantum computing emerged from the coming together of clever ideas and advancements in labs, a mix of quantum physics and information science.
We can develop quantum computers, but what else can we do?
We can also use superposition and entanglement for improved sensors and communications. We can make quantum sensors that measure things more precisely than classical physics allows. We can communicate information in quantum form that is resistant to eavesdropping. The challenge with these Quantum 2.0 things is making them practical. There is much work to do, and its very exciting to see the progress being made.
Another thing that makes quantum interesting is that there are potential applications in many areas, far beyond physics. There are applications being pursued in chemistry, biology, health care, finance, transport, manufacturing and so forth. It can be a very interdisciplinary field. That makes it hard because each one of us only has a certain amount of expertise. On the other hand, the cool part is you get to collaborate with people who are experts in other things and learn from them.
Illustration of the quantum physics concept known as superposition. In the ordinary classical world, a skateboarder could be in only one location or position at a time, such as the left side of the ramp (which could represent a data value of 0) or the right side (representing a 1). But if a skateboarder could behave like a quantum object (such as an atom), he or she could be in a superposition of 0 and 1, effectively existing in both places at the same time.
Credit: N. Hanacek/NIST
People do tend to think of quantum as sort of a weird and abstract thing. Because most of the stuff we deal with in the real world pens, cars, coffee cups, etc. those things dont behave quantum mechanically in our everyday experience. Because quantum mechanics is not an everyday experience for most people, it can seem very strange.
But quantum is not just a theory, its just the way nature is. For those of us who work with this every day, its not mysterious or abstract. Its as practical as anything else that we deal with during the day, including pens and coffee.
As I said, there are lots of practical applications of quantum. There are parts of electronics that rely heavily on quantum mechanics. Health care, communication, lots of technology relies on it.
One of the most common practical applications is timekeeping. The only reason youre able to have a GPS on your phone or in your car is that youve got some atomic clocks in satellites. You may not know it, but youre using quantum superposition in those clocks, making sure you can figure out where youre going. So if Im supposed to be meeting my wife at a restaurant, and I dont know where it is, Im relying on quantum mechanics to get me there, to achieve that goal. This is an everyday use of quantum mechanics, looking at our phones and figuring out where were going.
Studying quantum may lead us to the next big thing, or a bunch of things, whatever the next laser or GPS may be. There are a lot of ideas out there for how we can use quantum, and people are frantically trying to figure out:
Economies are affected by Quantum 1.0, and theres a high probability that Quantum 2.0 will have another transformational impact. There are so many ideas floating around that people are excited about; thats why were doing this.
NIST specifically is doing this because we do measurement science to help spur innovation and competitiveness. People come to NIST with measurement problems, and often, we can overcome classical barriers to this measurement problem using quantum mechanics. Thats why NIST has been a leader in quantum mechanics since its earliest day because of the precision measurement involved.
The more you can measure something very precisely, the more you can make improvements to that technology. So theres a lovely cycle of measuring more precisely, improving the technology, and measuring more. But at some point, we hit the limit of the measurement scheme were using, and we have to develop a new approach. Measurement science is key to advancing technology. Thats how I think about it.
When I was a kid, I liked building and fixing things. My bike would break, and it was the way I got around, so I was highly motivated to figure out how to fix it. So, I pulled things apart and put them back together again. I tinkered with things. I had some people around me who had knowledge of electronics, and I started building little simple circuits or simple gadgets with little motors or lights.
I wanted to understand how things work. Why is it doing this thing? And I was curious and got drawn into things. It helps to have a high tolerance for being confused. I want to say that physicists are perpetually confused about the latest thing theyre thinking about, and that is the way we learn, right? Youre confused today. You figure something out, and youre very happy about this, but youll be confused by something new tomorrow!
When I got into the lab, I found I was pretty good at fixing things, making things work, and understanding why things dont work and fixing those things. So, when you have that kind of inclination, you wind up as an experimentalist.
NIST researcher Andrew Wilson points to an ion trap inside a glass vacuum envelope. This trap is used for quantum computing. It can confine more than one atomic element (beryllium and magnesium) at the same time. NIST pioneered this capability, and its now being used by companies working on quantum computing.
Credit: R. Jacobson/NIST
And as for quantum, its just cool, right? For example, I do a lot of work with lasers. Theres almost nothing cooler than lasers. If youve only seen the little red dots of a laser pointer, come into some of these labs, and youll see the most incredible colors in nature. Its basically a rainbow on steroids. Theyre so beautiful and just wonderful to be around. Theres also a profound sense of joy from seeing something that no one has ever seen before, sometimes a discovery that scientists have been seeking for decades.
The lab feels like a playground to me, albeit with a challenging scientific mission, hard work, long hours, occasional setbacks, and serious safety requirements that require careful following of protocols.
A lab is like Disneyland to an experimental physicist like me. When youre in the lab and you see on your screen a signal, an image, a trace of something, after all that hard work, its just a reminder of how incredible nature really is. Its better than any fiction book thats ever been written in my humble opinion. This work just draws you in.
And of course, were not just tinkering around here, were mission-driven. We push very hard; its also a very competitive field. Many of us like to compete.
Theres a ton of really great science being done and quantum technologies being developed. We now do things in the lab routinely that even just a few years ago we only dreamed about being able to do and didnt know how. We can implement important algorithms for quantum computing. We can build sensing-type devices with quantum performance far beyond what anyone has had before. We can communicate quantum information over greater distances and with better fidelity than ever before.
There are different sorts of quantum computers that many companies are now building. NIST is developing ideas and technologies that these companies will need in the future as they try to extend the capabilities of their machines.
Many things about how quantum technologies might evolve remain unclear, but we as scientists are just very patient, slowly chipping away at problems. When youre chasing after something really important, that can be massively transformative, you have to have a lot of resilience and grit.
Scientists hammer things out improve things by factors of two year after year. Its like a running a marathon. We have our 100-meter races, too, but quantum is really a sustained effort. NIST has had a sustained quantum effort for decades now.
As we begin to work on potential applications of quantum, were learning so much about things beyond quantum physics. Its exciting to support companies that are part of the emerging quantum industry and to see the creative ways they are advancing technologies. Perhaps we will be able to look back at this moment in time as when quantum revolutionized technology, in the same way that silicon chips and integrated circuits did in the 1960s and 70s. I hope so. We shall see.
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From GPS to Laser Pointers, Quantum Science Is All Around Us - NIST
The first black hole portrait got sharper thanks to machine learning – Science News Magazine
If the first image of a black hole looked like a fuzzy doughnut, this one is a thin onion ring.
Using a machine learning technique, scientists have sharpened the portrait of the supermassive black hole at the center of galaxy M87, revealing a thinner halo of glowing gas than seen previously.
In 2019, scientists with the Event Horizon Telescope unveiled an image of M87s black hole (SN: 4/10/19). The picture was the first ever taken of a black hole and showed a blurry orange ring of swirling gas silhouetted by the dark behemoth. The new rings thickness is half that of the original, despite being based on the same data, researchers report April 13 in the Astrophysical Journal Letters.
The Event Horizon Telescope takes data using a network of telescopes across the globe. But that technique leaves holes in the data. Since we cant just cover the entire Earth in telescopes, what that means is that there is some missing information, says astrophysicist Lia Medeiros of the Institute for Advanced Study in Princeton, N.J. We need to have an algorithm that can fill in those gaps.
Previous analyses had used certain assumptions to fill in those gaps, such as preferring an image that is smooth. But the new technique uses machine learning to fill in those gaps based on over 30,000 simulated images of matter swirling around a black hole, creating a sharper image.
In the future, this technique could help scientists get a better handle on the black holes mass and perform improved tests of gravity and other studies of black hole physics.
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Physics writer Emily Conover has a Ph.D. in physics from the University of Chicago. She is a two-time winner of the D.C. Science Writers Association Newsbrief award.
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The first black hole portrait got sharper thanks to machine learning - Science News Magazine
Videos of gold nanoparticles snapping together show how some … – Science News Magazine
Mesmerizing videos offer a new look at the ways crystals form.
The real-time clips, described March 30 in Nature Nanotechnology, show closeup views of microscopic gold particles tumbling, sliding and flitting about before clicking into place in crystalline structures.
Before embarking on the study, physicist Erik Luijten of Northwestern University in Evanston, Ill., had expected to simply confirm century-old perceptions about how crystals form. But, he says, there was still so much to discover about crystallization.
Atoms that make up familiar crystals such as salt, sugar and quartz are hard to image in action. So the team turned to gold nanoparticles, each about 60 billionths of a meter across, or roughly one-thousandth the diameter of a typical human hair. The researchers used transmission electron microscopy to track the particles as they snapped into position after floating in a salty fluid.
Among the surprises in the videos, Luijten says, is the way crystallization depended on the gold nanoparticles skittering across crystal surfaces, as well as how the particles rapidly made their way to the growing crystals from the surrounding fluid. The videos allowed the researchers to find ways to control both of those processes.
By adjusting the chemistry of the fluid, the researchers tuned the rate at which the nanoparticles were deposited from the surrounding solution to build up the crystals. Choosing among shapes including cubes, cubes with indented faces and spheres changed how the particles moved along the crystals. By changing both fluid chemistry and particle shape, the researchers controlled whether the nanoparticle crystals grew smooth planes or rough surfaces.
The nanoparticles are hundreds of times the size of atoms. But the researchers think that atoms grow into crystals in much the same way, making the nanoparticles handy stand-ins. The study could aid in the design of bendable electronics, high-efficiency solar cells and other materials with properties that rely on crystal structures (SN: 6/1/18; SN: 7/26/17).
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James Riordon is a freelance science writer and coauthor of the bookGhost ParticleIn Search of the Elusive and Mysterious Neutrino.
Our mission is to provide accurate, engaging news of science to the public. That mission has never been more important than it is today.
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Videos of gold nanoparticles snapping together show how some ... - Science News Magazine
College of Science and Mathematics Student Named a Goldwater … – University of Massachusetts Boston
Kenji Maeda, a second-year engineering physics major, was named a 2023 Barry M. Goldwater Scholar. This is the fifth consecutive year that a UMass Boston student has been selected to receive the esteemed award, and the third time in the last five years that a student from the Physics Department has been chosen.
The Goldwater Scholarship Program is designed to foster and encourage outstanding college sophomores and juniors to pursue research careers in mathematics, natural sciences, and engineering. Undergraduate students who receive the award demonstrate a passion for doing research and also exhibit the creative spark that can lead to becoming leaders in their fields.
We are extremely proud of Kenji Maeda and also of the support for research excellence that is a hallmark of the UMass Boston Physics Department, said Chancellor Marcelo Surez-Orozco. The Goldwater Scholarship is considered the preeminent scholarship in the nation for undergraduates planning to pursue PhDs in science and mathematics fields. This is a highly impressive achievement.
Maedas path in quantum physics began last summer when he noticed a poster advertising Assistant Professor of Physics Akira Sones Quantum Information course. He took the class, along with a class on the fundamentals of quantum physics with Professor and Physics Department Chair Rahul Kulkarni. Mid-semester, Sone invited Maeda to join his quantum thermodynamics research team and encouraged him to develop a strong foundation by reading a wide range of literature on quantum physics.
Kenji is a remarkable student, Sone said. Earning a Goldwater scholarship is a result of his dedication to his work in quantum information theory, his love and intuition for physics, and his exceptional mathematical skill in analytics and numerics.
Our faculty are humbled and thrilled that the rigorous research in quantum physics taking place at UMass Boston provides opportunities and support for students to achieve the highest levels of academic excellence and sets them up for exciting futures in the field.
Maeda explained he is working on a project about quantum thermodynamics to explain the laws of thermodynamics from the perspective of quantum information science.
In our research group, we are examining how the application of our special measurement scheme on quantum systems would yield informative results compared to using other measurement schemes, Maeda said.
He is looking forward to taking advanced physics courses and upper-level engineering courses during his junior and senior yearsespecially Quantum Information II & IV. Once he completes his undergraduate degree, he intends to pursue a PhD in physics.
In the future, I would like to contribute to the development of quantum-related technology such as quantum computer, sensing, and communication, Maeda said.
Deeply appreciative of the inspiration, guidance, and spirit of collaboration from faculty such as Sone and Kulkarni, along with Assistant Professor Sumientra Rampersad, and Assistant Professor Olga Goulko, and his classmates and physics graduate students, Maeda said, I have earned this honor with everyone.
Goldwater scholarships are awarded annually by the Barry Goldwater Scholarship and Excellence in Education Foundation, an organization established by Congress in 1986 to honor the lifetime work of the late Arizona Senator Barry Goldwater. From an estimated pool of over 5,000 college sophomores and juniors, 1,267 natural science, engineering and mathematics students were nominated by 427 academic institutions to compete for the 2023 Goldwater scholarships. This year, 413 scholarships were awarded.
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Great Mysteries of Physics: do we really need a theory of everything? – Yahoo News UK
Finding a theory of everything explaining all the forces and particles in the universe is arguably the holy grail of physics. While each of its main theories works extraordinarily well, they clash also with each other leaving physicists to search for a deeper, more fundamental theory.
But do we really need a theory of everything? And are we anywhere near achieving one? Thats what we discuss in the sixth and final episode of our Great Mysteries of Physics podcast hosted by me, Miriam Frankel, science editor at The Conversation, and supported by FQxI, the Foundational Questions Institute.
Our two best theories of nature are quantum mechanics and general relativity, describing the smallest and biggest scales of the universe, respectively. Each is tremendously successful and has been experimentally tested over and over. The trouble is, they are incompatible with one another in many ways including mathematically.
General relativity is all about geometry. Its how space is curved and how space-time this unified entity that contains three dimensions of space and one dimension of time is itself also curved, explains Vlatko Vedral, a professor of physics at Oxford University in the UK. Quantum physics is actually all about algebra.
Physicists have already managed to unite quantum theory with Einsteins other big theory: special relativity (explaining how speed affects mass, time and space). Together, these form a framework called quantum field theory, which is the basis for the Standard Model of Particle Physics our best framework for describing the most basic building blocks of the universe.
The standard model describes three out of the four fundamental forces in the universe electromagnetism, and the strong and weak forces which govern the atomic nucleus excluding gravity.
While the standard model explains most of what we see in particle physics experiments, there are a few gaps. To bridge these, an extension called supersymmetry, suggesting particles are connected through a deep relationship, has been proposed. Supersymmetry suggests each particle has a super partner with the same mass, but opposite spin. Unfortunately, particle accelerators such as the Large Hadron Collider (LHC) at Cern in Switzerland have failed to find evidence of supersymmetry despite being explicitly designed to do so.
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On the other hand, there are recent hints from both LHC and Fermilab in the US suggesting that there may be a fifth force of nature. If these results could be replicated and confirmed as actual discoveries, that would have implications for uniting quantum mechanics and gravity.
I think [the discovery of a new force] would be amazing, says Vedral. It would challenge this thing that that has now existed for well over half a century that there are four fundamental forces.
Vedral argues the first thing to do if we discovered a fifth force would be to establish whether it can be described by quantum mechanics.
If it could, it would indicate that quantum theory might ultimately be more fundamental than general relativity, accounting for four out of five forces suggesting general relativity ultimately may need to be modified. If it couldnt, that would shake up physics suggesting we may need to modify quantum mechanics, too.
But what should a theory of everything include? Would it be enough to unite gravity and quantum mechanics? And what about other mysterious properties such as dark energy, which causes the universe to expand at an accelerated rate, or dark matter, an invisible substance making up most of the matter in the universe?
As Chanda Prescod-Weinstein, an assistant professor in physics and astronomy at the University of New Hampshire in the US, explains, physicists prefer to use the term theory of quantum gravity over theory of everything.
Dark matter and dark energy are most of the matter energy content in the universe. So its not really a theory of everything if its not accounting for most of the matter energy content in the universe, she argues. This is why Im glad we dont actually use theory of everything in our work.
Although they might not explain everything, several proposed theories of quantum gravity exist. One is string theory, which suggests the universe is ultimately made up of tiny, vibrating strings. Another is loop quantum gravity, which suggests Einsteins space-time arises from quantum effects.
One of the strengths that people will point to with string theory is that string theory built on quantum field theory, explains Prescod-Weinstein. It brings the whole standard model with it, which loop quantum gravity doesnt do in the same way. But string theory also has its weaknesses, she argues, such as requiring extra dimensions that weve never seen any evidence of.
The theories are difficult to test experimentally requiring much more energy than we can produce in any laboratory. Vedral argues that while we ultimately cant directly probe the tiny scales needed to find evidence for theories of quantum gravity, it may be possible to amplify such effects so that we could indirectly observe them on larger scales with table-top experiments.
You can listen to Great Mysteries of Physics via any of the apps listed above, our RSS feed, or find out how else to listen here. You can also read a transcript of the episode here.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The Conversation
Vlatko Vedral has had funding from The Templeton and the Moore Foundations. Chanda Prescod-Weinstein has had funding from the NSF, DoE, NASA, FQxI and Heising-Simons Foundation. She is a member of the American Physical Society, American Astronomical Society, FQxI, NASEM Elementary Particle Physics: Progress and Promise Committee
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Great Mysteries of Physics: do we really need a theory of everything? - Yahoo News UK
World Quantum Day A Chance to Look in on NQIS Centers – HPCwire
The U.S. National Quantum Initiative Act (NQIA) is now four years old and the second World Quantum Day 4.14.23 is on Friday. Yes, it was chosen because the date 4.14 is a rounding of Plancks constant which is so foundational in quantum mechanics. While WQD activities are only loosely coordinated and lean heavily towards educational outreach, there are a few reports being issued to commemorate the day and demonstrate value.
WQD describes itself as, an initiative from quantum scientists from 65+ countries. It is a decentralized and bottom-up initiative, inviting all scientists, engineers, educators, communicators, entrepreneurs, technologists, historians, philosophers, artists, museologists, producers, etc., and their organisations, to develop their own activities, such as outreach talks, exhibitions, lab tours, panel discussions, interviews, artistic creations, etc., to celebrate the World Quantum Day around the World.
Its tough to get a bead on WQD activities because they are so diverse and self-directing. That said, at least one of the five National Quantum Information Sciences (NQIS) Centers created by the NQIA the Quantum System Accelerator (QSA) based at Lawrence Berkeley National Laboratories posted an article recapping its progress to date, following closely on the heels of a formal QSA Impact Report issued in March.
Both the article and report provide glimpse into the scope of activities being undertaken by the NQIS centers. QSA is highlighting five of its efforts. Here are three:
Other NQIS centers have periodically released similar kinds of reports and the WQD activities perhaps present a good moment to check out what the centers are up to. Listed below are brief descriptions of the NQIS centers, excerpted from DoE web site:
Q-NEXT Next Generation Quantum Science and Engineering
Director:David AwschalomLead Institution:Argonne National Laboratory
Q-NEXT will create a focused, connected ecosystem to deliver quantum interconnects, to establish national foundries, and to demonstrate communication links, networks of sensors, and simulation testbeds. In addition to enabling scientific innovation, Q-NEXT will build a quantum-smart workforce, create quantum standards by building a National Quantum Devices Database, and provide pathways to the practical commercialization of quantum technology by embedding industry in all aspects of its operations and incentivizing start-ups.
C2QA Co-design Center for Quantum Advantage
Director:Andrew HouckLead Institution:Brookhaven National Laboratory
C2QA aims to overcome the limitations of todays noisy intermediate scale quantum (NISQ) computer systems to achieve quantum advantage for scientific computations in high-energy, nuclear, chemical and condensed matter physics. The integrated five-year goal of C2QA is to deliver a factor of 10 improvement in each of software optimization, underlying materials and device properties, and quantum error correction, and to ensure these improvements combine to provide a factor of 1,000 improvement in appropriate computation metrics.
SQMS Superconducting Quantum Materials and Systems Center
Director:Anna GrassellinoLead Institution:Fermi National Accelerator Laboratory
The primary mission of SQMS is to achieve transformational advances in the major crosscutting challenge of understanding and eliminating the decoherence mechanisms in superconducting 2D and 3D devices, with the goal of enabling construction and deployment of superior quantum systems for computing and sensing. In addition to the scientific advances, SQMS will target tangible deliverables in the form of unique foundry capabilities and quantum testbeds for materials, physics, algorithms, and simulations that could broadly serve the national QIS ecosystem.
QSA Quantum Systems Accelerator
Director: Rick MullerLead Institution: Sandia National Laboratories
QSA aims to co-design the algorithms, quantum devices, and engineering solutions needed to deliver certified quantum advantage in scientific applications. QSAs multi-disciplinary team will pair advanced quantum prototypesbased on neutral atoms, trapped ions, and superconducting circuitswith algorithms specifically constructed for imperfect hardware to demonstrate optimal applications for each platform in scientific computing, materials science, and fundamental physics. The QSA will deliver a series of prototypes to broadly explore the quantum technology trade-space, laying the basic science foundation to accelerate the maturation of commercial technologies.
QSC The Quantum Science Center
Director:Travis HumbleLead Institution:Oak Ridge National Laboratory
QSC is dedicated to overcoming key roadblocks in quantum state resilience, controllability, and ultimately scalability of quantum technologies. This goal will be achieved through integration of the discovery, design, and demonstration of revolutionary topological quantum materials, algorithms, and sensors, catalyzing development of disruptive technologies. In addition to the scientific goals, integral to the activities of the QSC are development of the next generation of QIS workforce by creating a rich environment for professional development and close coordination with industry to transition new QIS applications to the private sector.
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World Quantum Day A Chance to Look in on NQIS Centers - HPCwire