From Symmetry: “How big can a fundamental particle be?”

From Symmetry<

09/29/20
Sarah Charley

Extremely massive fundamental particles could exist, but they would seriously mess with our understanding of quantum mechanics.

Illustration by Sandbox Studio, Chicago with Steve Shanabruch.

Fundamental particles are objects that are so small, they have no deeper internal structure.

There are about a dozen “matter” particles that scientists think are fundamental, and they come in a variety of sizes. For instance, the difference between the masses of the top quark and the electron is equivalent to the difference between the masses of an adult elephant and a mosquito.

Still, all of these masses are extremely tiny compared to what’s physically possible. The known laws of physics allow for fundamental particles with masses approaching the “Planck mass”: a whopping 22 micrograms, or about the mass of a human eyelash. To go back to our comparisons with currently known particles, if the top quark had the same mass as an elephant, then a fundamental particle at the Planck mass would weigh as much as the moon.

Could such a particle exist? According to CERN Theory Fellow Dorota Grabowska, scientists aren’t completely sure.

“Particles with a mass below the Planck scale can be elementary,” Grabowska says. “Above that scale, maybe not. But we don’t know.”

Scientists at particle accelerators such as the Large Hadron Collider at CERN are always on the look-out for undiscovered massive particles that could fill in the gaps of their models. Finding new particles is so important that the global physics community is discussing building larger colliders that could produce even more massive particles. US involvement in the LHC is supported by the US Department of Energy’s Office of Science and the National Science Foundation.

CERN FCC Future Circular Collider map.

ILC schematic, being planned for the Kitakami highland, in the Iwate prefecture of northern Japan.

China Circular Electron Positron Collider (CEPC) map. It would be housed in a hundred-kilometer- (62-mile-) round tunnel at one of three potential sites. The documents work under the assumption that the collider will be located near Qinhuangdao City around 200 miles east of Beijing.

If scientists found a fundamental particle with a mass above the Planck scale, they would need to revisit how they think about particle sizes. For the kind of research performed at the LHC, fundamental particles are all considered to be the same size—no size at all.

“When we think about the pure mathematics, elementary particles are, by definition, point-like,” Grabowska says. “They don’t have a size.”

Treating fundamental particles as points works well in particle physics because their masses are so small that gravity, which would have an effect on more massive objects, is not really a factor. It’s kind of like how truck drivers planning a trip don’t need to consider the effects of special relativity and time dilation. These effects are there, at some level, but they don’t have a noticeable impact on drive time.

But a fundamental particle above the Planck scale would sit at the threshold between two divergent mathematical models. Quantum mechanics describes objects that are very tiny, and general relativity describes objects that are very massive. But to describe a particle that is both very tiny and very massive, scientists need a new theory called quantum gravity.

Mathematically, physicists could no longer consider such a massive particle as a volume-less point. Instead, they would need to think about it behaving more like a wave.

The particle-wave duality concept was born about 100 years ago and states that subatomic particles have both particle-like and wave-like properties. When scientists think about an electron as a particle, they consider that it has no physical volume. But when they think about it as a wave, it extends throughout all the space it’s granted, such as the orbit around the nucleus of an atom. Both interpretations are correct, and scientists typically use the one that best suits their area of research.

The mass-to-radius ratio of these waves is important because it determines how they feel the effects of gravity. A super massive particle with tons of room to roam would barely feel the force of gravity. But if that same particle were confined to an extremely small space, it could collapse into a miniature black hole. Scientists at the LHC have searched for such tiny black holes—which would evaporate almost immediately—but so far have come up empty-handed.

According to Grabowska, quantum gravity is tricky because there is no way to experimentally test it with today’s existing technology. “We would need a collider 14 orders of magnitude more energetic than the LHC,” she says.

But thinking about the implications of finding such a particle helps theorists push the known laws of physics.

“Our model of particle physics breaks down when pushed to certain scales,” says Netta Engelhardt, a quantum gravity theorist at the Massachusetts Institute of Technology. “But that doesn’t mean that our universe doesn’t feature these regimes. If we want to understand massive objects at tiny scales, we need a model of quantum gravity.”

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Symmetry is a joint Fermilab/SLAC publication.

From CERN: “CERN meets quantum technology”

From CERN

28 September, 2020
Matthew Chalmers

The CERN Quantum Technology Initiative will explore the potential of devices harnessing perplexing quantum phenomena such as entanglement to enrich and expand its challenging research programme.

CERN AEgIS 1T antimatter trap stack

Today’s information and communication technology grew out of the invention and development of quantum mechanics during the last century. But, nifty as it is that billions of transistors can be packed into your smartphone or that photons are routed around the internet with the help of lasers, the devices underpinning the “first quantum revolution” merely rely on the weird properties of quantum mechanics – they don’t put them to use directly.

The CERN Quantum Technology Initiative (QTI), which was announced by CERN Director-General Fabiola Gianotti in June, sees CERN join a rapidly-growing global effort to bring about a “second quantum revolution” – whereby phenomena such as superposition and entanglement, which enable an object to be in two places at the same time or to influence another instantaneously, are exploited to build new computing, communication, sensing and simulation devices.

It is difficult to predict the impact of such quantum technologies on society, but for high-energy physics and CERN the benefits are clear. They include advanced computing algorithms to cope with future data-analysis challenges, ultrasensitive detectors to search for hidden-sector particles and gravitational waves, and the use of well-controlled quantum systems to simulate or reproduce the behaviour of complex many-body quantum phenomena for theoretical research.

Though relatively new to the quantum technologies scene, CERN is in the unique position of having in one place the diverse set of skills and technologies – including software, computing and data science, theory, sensors, cryogenics, electronics and material science – necessary for such a multidisciplinary endeavour. AEgIS at CERN’s Antiproton Decelerator, which is able to explore the multi-particle entangled nature of photons from positronium annihilation, is one of several examples of existing CERN experiments already working in relevant technology areas. CERN also provides valuable use cases to help compare classical and quantum approaches to certain applications, as demonstrated recently when a team at Caltech used a quantum computer comprising 1098 superconducting qubits to “rediscover” the Higgs boson from LHC data. CERN’s rich network of academic and industry relations working in unique collaborations such as CERN openlab is a further strength.

The path to CERN’s QTI began with a workshop on quantum computing in high-energy physics organised by CERN openlab in November 2018, which was followed by several initiatives, pilot projects and events. During the next three years, the initiative will assess the potential impact of quantum technologies on CERN and high-energy physics on the timescale of the HL-LHC (late 2030s) and beyond. Governance and operational instruments are being finalised and concrete R&D objectives are being defined in the four main quantum technologies areas: computing; sensing and metrology; communication; and simulation and information processing. The CERN QTI will also develop an international education and training programme in collaboration with experts, universities and industry, and identify mechanisms for knowledge sharing within the CERN Member States, the high-energy physics community, other scientific research communities and society at large.

“By taking part in this rapidly growing field, CERN not only has much to offer, but also stands to benefit directly from it,” says Alberto Di Meglio, coordinator of the CERN QTI and head of CERN openlab. “The CERN Quantum Technology Initiative, by helping structure and coordinate activities with our community and the many international public and private initiatives, is a vital step to prepare for this exciting quantum future.”

See the full article here.

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Meet CERN in a variety of places:

Quantum Diaries

Cern Courier

THE FOUR MAJOR PROJECT COLLABORATIONS

ATLAS

CERN ATLAS Image Claudia Marcelloni CERN/ATLAS

ALICE

CERN/ALICE Detector

CMS

LHCb

LHC

CERN map

CERN LHC Tunnel

SixTrack CERN LHC particles

From Niels Bohr Institute DK: “Quantum entanglement realized between distant large objects”

University of Copenhagen DK

From Niels Bohr Institute DK

28 September 2020
Eugene Simon Polzik, Professor
polzik@nbi.ku.dk
Phone: +45 35 32 54 24
Mobil: +45 23 38 20 45

A team of researchers at the Niels Bohr Institute, University of Copenhagen, have succeeded in entangling two very different quantum objects. The result has several potential applications in ultra-precise sensing and quantum communication and is now published in Nature Physics.

Light propagates through the atomic cloud shown in the center and then falls onto the SiN membrane shown on the left. As a result of interaction with light the precession of atomic spins and vibration of the membrane become quantum correlated. This is the essence of entanglement between the atoms and the membrane. Credit: Niels Bohr Institute DK.

Entanglement is the basis for quantum communication and quantum sensing. It can be understood as a quantum link between two objects which makes them behave as a single quantum object.

Now, researchers from the Niels Bohr Institute DK, University of Copenhagen DK, have succeeded in making entanglement between two distinctly different and distant objects. One is a mechanical oscillator, a vibrating dielectric membrane, and the other is a cloud of atoms, each acting as a tiny magnet – what physicists call spin. These very different entities have now become possible to entangle by connecting them with photons, particles of light.Atoms can be useful in processing quantum information and the membrane – or mechanical quantum systems in general – can be useful for storage of quantum information.

Professor Eugene Polzik, who led the effort, states that: “With this new technique, we are on route to pushing the boundaries of the possibilities of entanglement. The bigger the objects, the further apart they are, the more disparate they are, the more interesting entanglement becomes from both fundamental and applied perspectives. With the new result, entanglement between very different objects has become possible”.

What is entanglement and how is it applied?

In order to understand the full reach of the new result, it is important to understand exactly what the concept of entanglement means:

Sticking to the example of spins entangled with a mechanical membrane, imagine the position of the vibrating membrane and the tilt of the total spin of all atoms, akin to a spinning top. If both objects move randomly, but we can observe that both of them move right or left at the same time, we call it a correlation. Such correlated motion is normally limited to the so-called zero-point motion – the residual, uncorrelated motion of all matter that occurs even at absolute zero temperature. This limits our knowledge about any of the systems. In their experiment, Eugene Polzik’s team has entangled the systems, which means that they move in a correlated way with a precision better than the zero-point motion. “Quantum mechanics is like a double-edged sword – it gives us wonderful new technologies, but also limits precision of measurements which would seem just easy from a classical point of view” – says a team member, Michał Parniak. Entangled systems can remain perfectly correlated even if they are at a distance from each other – a feature that has puzzled researchers from the very birth of quantum mechanics more than 100 years ago.

PhD student Christoffer Østfeldt explains further: “Imagine the different ways of realizing quantum states as a kind of zoo of different realities or situations with very different qualities and potentials. If, for example, we wish to build a device of some sort, in order to exploit the different qualities they all possess and in which they perform different functions and solve a different task, it will be necessary to invent a language they are all able to speak. The quantum states need to be able to communicate, for us to use the full potential of the device. That’s what this entanglement between two elements in the zoo has shown we are now capable of”.

A specific example of perspectives of entangling different quantum objects is quantum sensing. Different objects possess sensitivity to different external forces. For example, mechanical oscillators are used as accelerometers and force sensors, whereas atomic spins are used in magnetometers. When only one of the two different entangled objects is subject to external perturbation, entanglement allows it to be measured with a sensitivity not limited by the object’s zero-point fluctuations.

The outlook for the future applications of the new technique

There is a fairly immediate possibility for application of the technique in sensing both for tiny oscillators and big ones. One of the biggest scientific pieces of news in recent years was the first detection of gravity waves, made by the Laser Interferometer Gravitational-wave Observatory (LIGO).

MIT /Caltech Advanced aLigo .

Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA.

Caltech/MIT Advanced aLigo detector installation Hanford, WA, USA.

VIRGO Gravitational Wave interferometer, near Pisa, Italy.

VIRGO Gravitational Wave interferometer, near Pisa, Italy.

LIGO senses and measures extremely faint waves caused by astronomical events in deep space, such as black hole mergers or neutron star mergers. The waves can be observed because they shake the mirrors of the interferometer. But even LIGO’s sensitivity is limited by quantum mechanics because the mirrors of the laser interferometer are also shaken by the zero-point fluctuations. Those fluctuations lead to noise preventing observation of the tiny motion of the mirrors caused by gravitational waves.

Limitless precision in measurements likely to be achievable

It is, in principle, possible to generate entanglement of the LIGO mirrors with an atomic cloud and thus cancel the zero-point noise of the mirrors in the same way as it does for the membrane noise in the present experiment. The perfect correlation between the mirrors and the atomic spins due to their entanglement can be used in such sensors to virtually erase uncertainty. It simply requires us to take information from one system and apply the knowledge to the other. In such a way, we could learn both about the position and the momentum of LIGO’s mirrors at the same time, entering a so-called quantum-mechanics-free subspace and taking a step towards limitless precision of measurements of motion. A model experiment demonstrating this principle is on the way at Eugene Polzik’s laboratory.

See the full article here .

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Stem Education Coalition

Niels Bohr Institute DK (Danish: Niels Bohr Institutet DK) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen DK, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute. Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

The University of Copenhagen (UCPH) DK (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

From Simons Foundation: “Infinitely Long Chains of Hydrogen Atoms Have Surprising Properties, Including a Metallic Phase”

From Simons Foundation

September 14, 2020
Thomas Sumner

Stacey Greenebaum
press@simonsfoundation.org.

Scientists with the Flatiron Institute and the Simons Collaboration on the Many Electron Problem combined cutting-edge computational methods to probe an endless line of protons surrounded by electrons.

A map of where electrons are most likely to be found around a chain of hydrogen atoms. Brighter colors denote higher probabilities. At this spacing between atoms, the electrons try to link pairs of adjacent atoms to form dihydrogen molecules. Because the protons are fixed in place, these molecules can’t form. Instead, each electron ‘leans’ toward a neighboring atom. M. Motta et al./Physical Review X 2020.

An infinite chain of hydrogen atoms is just about the simplest bulk material imaginable — a never-ending single-file line of protons surrounded by electrons. Yet a new computational study combining four cutting-edge methods finds that the modest material boasts fantastic and surprising quantum properties.

By computing the consequences of changing the spacing between the atoms, an international team of researchers from the Flatiron Institute and the Simons Collaboration on the Many Electron Problem found that the hydrogen chain’s properties can be varied in unexpected and drastic ways. That includes the chain transforming from a magnetic insulator into a metal, the researchers report September 14 in Physical Review X.

The computational methods used in the study present a significant step toward custom-designing materials with sought-after properties, such as the possibility of high-temperature superconductivity in which electrons flow freely through a material without losing energy, says the study’s senior author Shiwei Zhang. Zhang is a senior research scientist at the Center for Computational Quantum Physics (CCQ) at the Simons Foundation’s Flatiron Institute in New York City.

“The main purpose was to apply our tools to a realistic situation,” Zhang says. “Almost as a side product, we discovered all of this interesting physics of the hydrogen chain. We didn’t think that it would be as rich as it turned out to be.”

Zhang, who is also a chancellor professor of physics at the College of William and Mary, co-led the research with Mario Motta of IBM Quantum. Motta serves as first author of the paper alongside Claudio Genovese of the International School for Advanced Studies (SISSA) in Italy, Fengjie Ma of Beijing Normal University, Zhi-Hao Cui of the California Institute of Technology, and Randy Sawaya of the University of California, Irvine. Additional co-authors include CCQ co-director Andrew Millis, CCQ Flatiron Research Fellow Hao Shi and CCQ research scientist Miles Stoudenmire.

The paper’s long author list — 17 co-authors in total — is uncommon for the field, Zhang says. Methods are often developed within individual research groups. The new study brings many methods and research groups together to combine forces and tackle a particularly thorny problem. “The next step in the field is to move toward more realistic problems,” says Zhang, “and there is no shortage of these problems that require collaboration.”

While conventional methods can explain the properties of some materials, other materials, such as infinite hydrogen chains, pose a more daunting computational hurdle. That’s because the behavior of the electrons in those materials is heavily influenced by interactions between electrons. As electrons interact, they become quantum-mechanically entangled with one another. Once entangled, the electrons can no longer be treated individually, even when they are physically separate.

The sheer number of electrons in a bulk material — roughly 100 billion trillion per gram — means that conventional brute force methods can’t even come close to providing a solution. The number of electrons is so large that it’s practically infinite when thinking at the quantum scale.

Thankfully, quantum physicists have developed clever methods of tackling this many-electron problem. The new study combines four such methods: variational Monte Carlo, lattice-regularized diffusion Monte Carlo, auxiliary-field quantum Monte Carlo, and standard and sliced-basis density-matrix renormalization group. Each of these cutting-edge methods has its strengths and weaknesses. Using them in parallel and in concert provides a fuller picture, Zhang says.

Researchers, including authors of the new study, previously used those methods in 2017 to compute the amount of energy each atom in a hydrogen chain has as a function of the chain’s spacing [Physical Review X]. This computation, known as the equation of state, doesn’t provide a complete picture of the chain’s properties. By further honing their methods, the researchers did just that.

At large separations, the researchers found that the electrons remain confined to their respective protons. Even at such large distances, the electrons still ‘know’ about each other and become entangled. Because the electrons can’t hop from atom to atom as easily, the chain acts as an electrical insulator.

As the atoms move closer together, the electrons try to form molecules of two hydrogen atoms each. Because the protons are fixed in place, these molecules can’t form. Instead, the electrons ‘wave’ to one another, as Zhang puts it. Electrons will lean toward an adjacent atom. In this phase, if you find an electron leaning toward one of its neighbors, you’ll find that neighboring electron responding in return. This pattern of pairs of electrons leaning toward each other will continue in both directions.

Moving the hydrogen atoms even closer together, the researchers discovered that the hydrogen chain transformed from an insulator into a metal with electrons moving freely between atoms. Under a simple model of interacting particles known as the one-dimensional Hubbard model, this transition shouldn’t happen, as electrons should electrically repel each other enough to restrict movement. In the 1960s, British physicist Nevill Mott predicted the existence of an insulator-to-metal transition based on a mechanism involving so-called excitons, each consisting of an electron trying to break free of its atom and the hole it leaves behind. Mott proposed an abrupt transition driven by the breakup of these excitons — something the new hydrogen chain study didn’t see.

Instead, the researchers discovered a more nuanced insulator-to-metal transition. As the atoms move closer together, electrons gradually get peeled off the tightly bound inner core around the proton line and become a thin `vapor’ only loosely bound to the line and displaying interesting magnetic structures.

The infinite hydrogen chain will be a key benchmark in the future in the development of computational methods, Zhang says. Scientists can model the chain using their methods and check their results for accuracy and efficiency against the new study.

The new work is a leap forward in the quest to utilize computational methods to model realistic materials, the researchers say. In the 1960s, British physicist Neil Ashcroft proposed that metallic hydrogen, for instance, might be a high-temperature superconductor. While the one-dimensional hydrogen chain doesn’t exist in nature (it would crumple into a three-dimensional structure), the researchers say that the lessons they learned are a crucial step forward in the development of the methods and physical understanding needed to tackle even more realistic materials.

See the full article here.

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Mission and Model

The Simons Foundation’s mission is to advance the frontiers of research in mathematics and the basic sciences.

Co-founded in New York City by Jim and Marilyn Simons, the foundation exists to support basic — or discovery-driven — scientific research undertaken in the pursuit of understanding the phenomena of our world.

The Simons Foundation’s support of science takes two forms: We support research by making grants to individual investigators and their projects through academic institutions, and, with the launch of the Flatiron Institute in 2016, we now conduct scientific research in-house, supporting teams of top computational scientists.

From UC Santa Barbara: “Quantum Shake”

From UC Santa Barbara

September 9, 2020
Sonia Fernandez
(805) 893-4765
sonia.fernandez@ucsb.edu

There they were, in all their weird quantum glory: ultracold lithium atoms in the optical trap operated by UC Santa Barbara undergraduate student Alec Cao and his colleagues in David Weld’s atomic physics group. Held by lasers in a regular, lattice formation and “driven” by pulses of energy, these atoms were doing crazy things.

“It was a bit bizarre,” Weld said. “Atoms would get pumped in one direction. Sometimes they would get pumped in another direction. Sometimes they would tear apart and make these structures that looked like DNA.”

These new and unexpected behaviors were the results of an experiment conducted by Cao, Weld and colleagues to push the boundaries of our knowledge of the quantum world. The outcomes? New directions in the field of dynamical quantum engineering, and a tantalizing path toward a link between classical and quantum physics.

Their research is published in the journal Physical Review Research.

“A lot of funny things happen when you shake a quantum system,” said Weld, whose lab creates “artificial solids” — low-dimensional lattices of light and ultracold atoms — to simulate the behavior of quantum mechanical particles in more densely packed true solids when subjected to driving forces. The recent experiments were the latest in a line of reasoning that stretches back to 1929, when physicist and Nobel Laureate Felix Bloch first predicted that within the confines of a periodic quantum structure, a quantum particle under a constant force will oscillate.

“They actually slosh back and forth, which is a consequence of the wave nature of matter,” Weld said. While these position-space Bloch oscillations were predicted almost a century ago, they were directly observed only relatively recently; in fact Weld’s group was the first to see them in 2018 [Physical Review Letters], with a method that made these often rapid, infinitesimal sloshings large and slow, and easy to see.

A decade ago, other experiments added a time dependency to the Bloch oscillating system by subjecting it to an additional, periodic force, and found even more intense activity. Oscillations on top of oscillations — super Bloch oscillations — were discovered.

For this study, the researchers took the system another step further, by modifying the space in which these atoms interact.

“We’re actually changing the lattice,” said Weld, by way of varying laser intensities and external magnetic forces that not only added a time dependency but also curved the lattice, creating an inhomogenous force field. Their method of creating large, slow oscillations, he added, “gave us the opportunity to look at what happens when you have a Bloch oscillating system in an inhomogenous environment.”

This is when things got weird. The atoms shot back and forth, sometimes spreading apart, other times creating patterns in response to the pulses of energy pushing on the lattice in various ways.

“We could follow their progress with numerics if we worked hard at it,” Weld said. “But it was a little bit hard to understand why they do one thing and not the other.”

It was insight from Cao, the paper’s lead author, that led to a way of deciphering the strange behavior.

“When we investigated the dynamics for all times at once, we just saw a mess because there was no underlying symmetry, making the physics challenging to interpret,” said Cao, who is beginning his fourth year at UCSB’s College of Creative Studies.

To draw out the symmetry, the researchers simplified this seemingly chaotic behavior by eliminating a dimension (in this case, time) by utilizing a mathematical technique initially developed to observe classical nonlinear dynamics called a Poincaré section.

“In our experiment, a time interval is set by how we periodically modify the lattice in time,” Cao said. “When we chucked out all the ‘in-between’ times and looked at the behavior once every period, structure and beauty emerged in the shapes of the trajectories because we were properly respecting the symmetry of the physical system.” Observing the system only at periods based on this time interval yielded something like a stop-motion representation of these atoms’ complicated yet cyclical movements.

“What Alec figured is that these paths — these Poincaré orbits — tell us exactly why in some regimes of driving the atoms get pumped, while in other regimes of driving the atoms spread out and break up the wave function,” Weld added. One direction the researchers could take from here, he said, is to use this knowledge to engineer quantum systems to have new behaviors through driving, with applications in burgeoning fields such as topological quantum computing.

“But another direction we can take is looking at whether we can study the emergence of quantum chaos as we start to do things like add interactions to a driven system like this,” Weld said.

It’s no small feat. Physicists for decades have been trying to find links between classical and quantum physics — a common math that might explain concepts in one field that seem to have no analog in the other, such as classical chaos, the language for which does not exist in quantum mechanics.

“You’ve probably heard of the butterfly effect — a butterfly flapping its wings in the Caribbean can cause a typhoon somewhere across the world,” said Weld. “That’s actually a feature of classical chaotic systems, which have a sensitive dependence on initial conditions. That feature is actually very hard to reproduce in quantum systems — it’s puzzling to come up with the same explanation in quantum systems. So this is maybe a small piece of that body of research.”

See the full article here .

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The University of California, Santa Barbara (commonly referred to as UC Santa Barbara or UCSB) is a public research university and one of the 10 general campuses of the University of California system. Founded in 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944 and is the third-oldest general-education campus in the system. The university is a comprehensive doctoral university and is organized into five colleges offering 87 undergraduate degrees and 55 graduate degrees. In 2012, UCSB was ranked 41st among “National Universities” and 10th among public universities by U.S. News & World Report. UCSB houses twelve national research centers, including the renowned Kavli Institute for Theoretical Physics.

From Niels Bohr Institute: “Extracting order from a quantum measurement finally shown experimentally”

University of Copenhagen

From Niels Bohr Institute

4 September 2020

Professor Albert Schliesser
albert.schliesser@nbi.ku.dk

QUANTUM TECHNOLOGY: In physics, it is essential to be able to show a theoretical assumption in actual, physical experiments. For more than a hundred years, physicists have been aware of the link between the concepts of disorder in a system, and information obtained by measurement. However, a clean experimental assessment of this link in common monitored systems, that is systems which are continuously measured over time, was missing so far.

A thin silicon nitride membrane (white) is stretched tight across a silicon frame (red). The membrane contains a pattern of holes, with one small island in the center, whose vibrations are measured in the experiment.

But now, using a “quantum drum”, a vibrating, mechanical membrane, researchers at the Niels Bohr Institute, University of Copenhagen, have realized an experimental setup that shows the physical interplay between the disorder and the outcomes of a measurement. Most importantly, these outcomes allow to extract order from the largely disordered system, providing a general tool to engineer the state of the system, essential for future quantum technologies, like quantum computers. The result is now published in as an Editors’ Suggestion in Physical Review Letters.

Measurements will always introduce a level of disturbance of any system it measures. In the ordinary, physical world, this is usually not relevant, because it is perfectly possible for us to measure, say, the length of a table without noticing that disturbance. But on the quantum scale, like the movements of the membranes used in the Schliesser lab at the Niels Bohr Institute, the consequences of the disturbance made by measurements are huge. These large disturbances increase the entropy, or disorder, of the underlying system, and apparently preclude to extract any order from the measurement. But before explaining how the recent experiment realized this, the concepts of entropy and thermodynamics need a few words.

Breaking an egg is thermodynamics.

The law of thermodynamics covers extremely complicated processes. The classic example is that if an egg falls off of a table, it breaks on the floor. In the collision, heat is produced – among many other physical processes – and if you imagine you could control all of these complicated processes, there is nothing in the physical laws that say you can’t reverse the process. In other words, the egg could actually assemble itself and fly up to the table surface again, if we could control the behavior of every single atom, and reverse the process. It is theoretically possible. You can also think of an egg as an ordered system, and if it breaks, it becomes extremely disordered. Physicists say that the entropy, the amount of disorder, has increased. The laws of thermodynamics tell us that the disorder will in fact always increase, not the other way round: So eggs do not generally jump off floors, assemble and land on tables in the real world.

Correct quantum system readouts are essential – and notoriously difficult to obtain.

If we turn to quantum mechanics, the world looks rather different, and yet the same. If we continuously measure the displacement of a mechanical, moving system like the “membrane-drum” with a precision only limited by the quantum laws, this measurement disturbs the movement profoundly. So you will end up measuring a displacement which is disturbed during the measurement process itself, and the readout of the original displacement will be spoiled – unless you can measure the introduced disorder as well. In this case, you can use the information about the disorder to reduce the entropy produced by the measurement and generate order from it – comparable to controlling the disorder in the shattered egg-system. But this time we have the information on the displacement as well, so we have learnt something about the entire system along the way, and, crucially, we have access to the original vibration of the membrane, i.e. the correct readout.

A generalized framework for understanding entropy in quantum systems.

“The connection between thermodynamics and quantum measurements has been known for more than a century. However, an experimental assessment of this link was missing so far, in the context of continuous measurements. That is exactly what we have done with this experiment. It is absolutely essential that we understand how measurements produce entropy and disorder in quantum systems, and how we use it in order to have control over the readouts we shall have in the future from, say, a quantum system like a quantum computer. If we are not able to control the disturbances, we basically won’t be able to understand the readouts – and the quantum computer readouts will be illegible, and useless, of course”, says Massimiliano Rossi, PhD student and first author on the scientific article. “This framework is important in order to create a generalized basic foundation for our understanding of entropy producing systems on the quantum scale. That’s basically where this study fits into the grander scale of things in physics”.

See the full article here .

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Stem Education Coalition

Niels Bohr Institute (Danish: Niels Bohr Institutet) is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics.

The Institute was founded in 1921, as the Institute for Theoretical Physics of the University of Copenhagen, by the Danish theoretical physicist Niels Bohr, who had been on the staff of the University of Copenhagen since 1914, and who had been lobbying for its creation since his appointment as professor in 1916. On the 80th anniversary of Niels Bohr’s birth – October 7, 1965 – the Institute officially became The Niels Bohr Institute.[1] Much of its original funding came from the charitable foundation of the Carlsberg brewery, and later from the Rockefeller Foundation.[2]

During the 1920s, and 1930s, the Institute was the center of the developing disciplines of atomic physics and quantum physics. Physicists from across Europe (and sometimes further abroad) often visited the Institute to confer with Bohr on new theories and discoveries. The Copenhagen interpretation of quantum mechanics is named after work done at the Institute during this time.

On January 1, 1993 the institute was fused with the Astronomic Observatory, the Ørsted Laboratory and the Geophysical Institute. The new resulting institute retained the name Niels Bohr Institute.

The University of Copenhagen (UCPH) (Danish: Københavns Universitet) is the oldest university and research institution in Denmark. Founded in 1479 as a studium generale, it is the second oldest institution for higher education in Scandinavia after Uppsala University (1477). The university has 23,473 undergraduate students, 17,398 postgraduate students, 2,968 doctoral students and over 9,000 employees. The university has four campuses located in and around Copenhagen, with the headquarters located in central Copenhagen. Most courses are taught in Danish; however, many courses are also offered in English and a few in German. The university has several thousands of foreign students, about half of whom come from Nordic countries.

The university is a member of the International Alliance of Research Universities (IARU), along with University of Cambridge, Yale University, The Australian National University, and UC Berkeley, amongst others. The 2016 Academic Ranking of World Universities ranks the University of Copenhagen as the best university in Scandinavia and 30th in the world, the 2016-2017 Times Higher Education World University Rankings as 120th in the world, and the 2016-2017 QS World University Rankings as 68th in the world. The university has had 9 alumni become Nobel laureates and has produced one Turing Award recipient

From Rice University: “Quantum leap for speed limit bounds”

From Rice University

September 2, 2020
Jade Boyd

Rice physicists set far-more-accurate limits on speed of quantum information.

A Wang-Hazzard commutativity graph captures the microscopic detail of the mathematical functions physicists typically use to describe energy in quantum systems, reducing the calculation of quantum speed limits to an equation with just two inputs. (Image courtesy of Zhiyuan Wang/Rice University)

Nature’s speed limits aren’t posted on road signs, but Rice University physicists have discovered a new way to deduce them that is better — infinitely better, in some cases — than previous methods.

“The big question is, ‘How fast can anything — information, mass, energy — move in nature?’” said Kaden Hazzard, a theoretical quantum physicist at Rice. “It turns out that if somebody hands you a material, it is incredibly difficult, in general, to answer the question.”

In a study published today in the American Physical Society journal PRX Quantum, Hazzard and Rice graduate student Zhiyuan Wang describe a new method for calculating the upper bound of speed limits in quantum matter.

“At a fundamental level, these bounds are much better than what was previously available,” said Hazzard, an assistant professor of physics and astronomy and member of the Rice Center for Quantum Materials. “This method frequently produces bounds that are 10 times more accurate, and it’s not unusual for them to be 100 times more accurate. In some cases, the improvement is so dramatic that we find finite speed limits where previous approaches predicted infinite ones.”

Nature’s ultimate speed limit is the speed of light, but in nearly all matter around us, the speed of energy and information is much slower. Frequently, it is impossible to describe this speed without accounting for the large role of quantum effects.

In the 1970s, physicists proved that information must move much slower than the speed of light in quantum materials, and though they could not compute an exact solution for the speeds, physicists Elliott Lieb and Derek Robinson pioneered mathematical methods for calculating the upper bounds of those speeds.

“The idea is that even if I can’t tell you the exact top speed, can I tell you that the top speed must be less than a particular value,” Hazzard said. “If I can give a 100% guarantee that the real value is less than that upper bound, that can be extremely useful.”

Hazzard said physicists have long known that some of the bounds produced by the Lieb-Robinson method are “ridiculously imprecise.”

“It might say that information must move less than 100 miles per hour in a material when the real speed was measured at 0.01 miles per hour,” he said. “It’s not wrong, but it’s not very helpful.”

The more accurate bounds described in the PRX Quantum paper were calculated by a method Wang created.

“We invented a new graphical tool that lets us account for the microscopic interactions in the material instead of relying only on cruder properties such as its lattice structure,” Wang said.

Hazzard said Wang, a third-year graduate student, has an incredible talent for synthesizing mathematical relationships and recasting them in new terms.

“When I check his calculations, I can go step by step, churn through the calculations and see that they’re valid,” Hazzard said. “But to actually figure out how to get from point A to point B, what set of steps to take when there’s an infinite variety of things you could try at each step, the creativity is just amazing to me.”

The Wang-Hazzard method can be applied to any material made of particles moving in a discrete lattice. That includes oft-studied quantum materials like high-temperature superconductors, topological materials, heavy fermions and others. In each of these, the behavior of the materials arises from interactions of billions upon billions of particles, whose complexity is beyond direct calculation.

Hazzard said he expects the new method to be used in several ways.

“Besides the fundamental nature of this, it could be useful for understanding the performance of quantum computers, in particular in understanding how long they take to solve important problems in materials and chemistry,” he said.

Hazzard said he is certain the method will also be used to develop numerical algorithms because Wang has shown it can put rigorous bounds on the errors produced by oft-used numerical techniques that approximate the behavior of large systems.

A popular technique physicists have used for more than 60 years is to approximate a large system by a small one that can be simulated by a computer.

“We draw a small box around a finite chunk, simulate that and hope that’s enough to approximate the gigantic system,” Hazzard said. “But there has not been a rigorous way of bounding the errors in these approximations.”

The Wang-Hazzard method of calculating bounds could lead to just that.

“There is an intrinsic relationship between the error of a numerical algorithm and the speed of information propagation,” Wang explained, using the sound of his voice and the walls in his room to illustrate the link.

“The finite chunk has edges, just as my room has walls. When I speak, the sound will get reflected by the wall and echo back to me. In an infinite system, there is no edge, so there is no echo.”

In numerical algorithms, errors are the mathematical equivalent of echoes. They reverberate from the edges of the finite box, and the reflection undermines the algorithms’ ability to simulate the infinite case. The faster information moves through the finite system, the shorter the time the algorithm faithfully represents the infinite.

Hazzard said he, Wang and others in his research group are using their method to craft numerical algorithms with guaranteed error bars.

“We don’t even have to change the existing algorithms to put strict, guaranteed error bars on the calculations,” he said. “But you can also flip it around and use this to make better numerical algorithms. We’re exploring that, and other people are interested in using these as well.”

The research was supported by the Welch Foundation and the National Science Foundation.

See the full article here .

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Stem Education Coalition

In his 1912 inaugural address, Rice University president Edgar Odell Lovett set forth an ambitious vision for a great research university in Houston, Texas; one dedicated to excellence across the range of human endeavor. With this bold beginning in mind, and with Rice’s centennial approaching, it is time to ask again what we aspire to in a dynamic and shrinking world in which education and the production of knowledge will play an even greater role. What shall our vision be for Rice as we prepare for its second century, and how ought we to advance over the next decade?

This was the fundamental question posed in the Call to Conversation, a document released to the Rice community in summer 2005. The Call to Conversation asked us to reexamine many aspects of our enterprise, from our fundamental mission and aspirations to the manner in which we define and achieve excellence. It identified the pressures of a constantly changing and increasingly competitive landscape; it asked us to assess honestly Rice’s comparative strengths and weaknesses; and it called on us to define strategic priorities for the future, an effort that will be a focus of the next phase of this process.

From Griffith University via Science Alert: “Physicists Just Found a New Quantum Paradox That Casts Doubt on a Pillar of Reality”

From Griffith University

via

Science Alert

28 AUGUST 2020
ERIC CAVALCANTI

(Paolo Carnassale/Getty Images.)

If a tree falls in a forest and no one is there to hear it, does it make a sound? Perhaps not, some say.

And if someone is there to hear it? If you think that means it obviously did make a sound, you might need to revise that opinion.

We have found a new paradox in quantum mechanics [Nature Physics] – one of our two most fundamental scientific theories, together with Einstein’s theory of relativity – that throws doubt on some common-sense ideas about physical reality.

Quantum mechanics vs common sense

Take a look at these three statements:

When someone observes an event happening, it really happened.

It is possible to make free choices, or at least, statistically random choices.

A choice made in one place can’t instantly affect a distant event. (Physicists call this “locality”.)

These are all intuitive ideas, and widely believed even by physicists. But our research, published in Nature Physics, shows they cannot all be true – or quantum mechanics itself must break down at some level.

This is the strongest result yet in a long series of discoveries in quantum mechanics that have upended our ideas about reality. To understand why it’s so important, let’s look at this history.

The battle for reality

Quantum mechanics works extremely well to describe the behaviour of tiny objects, such as atoms or particles of light (photons). But that behaviour is … very odd.

In many cases, quantum theory doesn’t give definite answers to questions such as “where is this particle right now?” Instead, it only provides probabilities for where the particle might be found when it is observed.

For Niels Bohr, one of the founders of the theory a century ago, that’s not because we lack information, but because physical properties like “position” don’t actually exist until they are measured.

And what’s more, because some properties of a particle can’t be perfectly observed simultaneously – such as position and velocity – they can’t be real simultaneously.

No less a figure than Albert Einstein found this idea untenable. In a 1935 article [Physical Review Journals Archive] with fellow theorists Boris Podolsky and Nathan Rosen, he argued there must be more to reality than what quantum mechanics could describe.

The article considered a pair of distant particles in a special state now known as an “entangled” state. When the same property (say, position or velocity) is measured on both entangled particles, the result will be random – but there will be a correlation between the results from each particle.

For example, an observer measuring the position of the first particle could perfectly predict the result of measuring the position of the distant one, without even touching it. Or the observer could choose to predict the velocity instead. This had a natural explanation, they argued, if both properties existed before being measured, contrary to Bohr’s interpretation.

However, in 1964 Northern Irish physicist John Bell [Nature] found Einstein’s argument broke down if you carried out a more complicated combination of different measurements on the two particles.

Bell showed that if the two observers randomly and independently choose between measuring one or another property of their particles, like position or velocity, the average results cannot be explained in any theory where both position and velocity were pre-existing local properties.

That sounds incredible, but experiments have now conclusively demonstrated Bell’s correlations do occur. For many physicists, this is evidence that Bohr was right: physical properties don’t exist until they are measured.

But that raises the crucial question: what is so special about a “measurement”?

The observer, observed

In 1961, the Hungarian-American theoretical physicist Eugene Wigner devised a thought experiment to show what’s so tricky about the idea of measurement.

He considered a situation in which his friend goes into a tightly sealed lab and performs a measurement on a quantum particle – its position, say.

However, Wigner noticed that if he applied the equations of quantum mechanics to describe this situation from the outside, the result was quite different. Instead of the friend’s measurement making the particle’s position real, from Wigner’s perspective the friend becomes entangled with the particle and infected with the uncertainty that surrounds it.

This is similar to Schrödinger’s famous cat, a thought experiment in which the fate of a cat in a box becomes entangled with a random quantum event.

For Wigner, this was an absurd conclusion. Instead, he believed that once the consciousness of an observer becomes involved, the entanglement would “collapse” to make the friend’s observation definite.

But what if Wigner was wrong?

Our experiment

In our research, we built on an extended version of the Wigner’s friend paradox, first proposed [MDPI] by Časlav Brukner of the University of Vienna. In this scenario, there are two physicists – call them Alice and Bob – each with their own friends (Charlie and Debbie) in two distant labs.

There’s another twist: Charlie and Debbie are now measuring a pair of entangled particles, like in the Bell experiments.

As in Wigner’s argument, the equations of quantum mechanics tell us Charlie and Debbie should become entangled with their observed particles. But because those particles were already entangled with each other, Charlie and Debbie themselves should become entangled – in theory.

But what does that imply experimentally?

Our experiment goes like this: the friends enter their labs and measure their particles. Some time later, Alice and Bob each flip a coin. If it’s heads, they open the door and ask their friend what they saw. If it’s tails, they perform a different measurement.

This different measurement always gives a positive outcome for Alice if Charlie is entangled with his observed particle in the way calculated by Wigner. Likewise for Bob and Debbie.

In any realisation of this measurement, however, any record of their friend’s observation inside the lab is blocked from reaching the external world. Charlie or Debbie will not remember having seen anything inside the lab, as if waking up from total anaesthesia.

But did it really happen, even if they don’t remember it?

If the three intuitive ideas at the beginning of this article are correct, each friend saw a real and unique outcome for their measurement inside the lab, independent of whether or not Alice or Bob later decided to open their door. Also, what Alice and Charlie see should not depend on how Bob’s distant coin lands, and vice versa.

We showed that if this were the case, there would be limits to the correlations Alice and Bob could expect to see between their results. We also showed that quantum mechanics predicts Alice and Bob will see correlations that go beyond those limits.

Next, we did an experiment to confirm the quantum mechanical predictions using pairs of entangled photons. The role of each friend’s measurement was played by one of two paths each photon may take in the setup, depending on a property of the photon called “polarisation”. That is, the path “measures” the polarisation.

Our experiment is only really a proof of principle, since the “friends” are very small and simple. But it opens the question whether the same results would hold with more complex observers.

We may never be able to do this experiment with real humans. But we argue that it may one day be possible to create a conclusive demonstration if the “friend” is a human-level artificial intelligence running in a massive quantum computer.

What does it all mean?

Although a conclusive test may be decades away, if the quantum mechanical predictions continue to hold, this has strong implications for our understanding of reality – even more so than the Bell correlations.

For one, the correlations we discovered cannot be explained just by saying that physical properties don’t exist until they are measured.

Now the absolute reality of measurement outcomes themselves is called into question.

Our results force physicists to deal with the measurement problem head on: either our experiment doesn’t scale up, and quantum mechanics gives way to a so-called “objective collapse theory”, or one of our three common-sense assumptions must be rejected.

There are theories, like de Broglie-Bohm, that postulate “action at a distance”, in which actions can have instantaneous effects elsewhere in the universe. However, this is in direct conflict with Einstein’s theory of relativity.

Some search for a theory that rejects freedom of choice, but they either require backwards causality, or a seemingly conspiratorial form of fatalism called “superdeterminism”.

Another way to resolve the conflict could be to make Einstein’s theory even more relative. For Einstein, different observers could disagree about when or where something happens – but what happens was an absolute fact.

However, in some interpretations, such as relational quantum mechanics, QBism, or the many-worlds interpretation, events themselves may occur only relative to one or more observers. A fallen tree observed by one may not be a fact for everyone else.

All of this does not imply that you can choose your own reality. Firstly, you can choose what questions you ask, but the answers are given by the world. And even in a relational world, when two observers communicate, their realities are entangled. In this way a shared reality can emerge.

Which means that if we both witness the same tree falling and you say you can’t hear it, you might just need a hearing aid.

See the full article here .

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Stem Education Coalition

In 1971, Griffith was created to be a new kind of university—one that offered new degrees in progressive fields such as Asian studies and environmental science. At the time, these study areas were revolutionary—today, they’re more important than ever.

Since then, we’ve grown into a comprehensive, research-intensive university, ranking in the top 5% of universities worldwide. Our teaching and research spans five campuses in South East Queensland and all disciplines, while our network of more than 120,000 graduates extends around the world.

Griffith continues the progressive traditions of its namesake, Sir Samuel Walker Griffith, who was twice the Premier of Queensland, the first Chief Justice of the High Court of Australia, and the principal author of the Australian Constitution.

From Lawrence Berkeley National Lab: “New $115 Million Quantum Systems Accelerator to Pioneer Quantum Technologies for Discovery Science”

From Lawrence Berkeley National Lab

August 26, 2020
Dan Krotz
dakrotz@lbl.gov
510-220-8529

Berkeley Lab-led center to catalyze U.S. leadership in quantum information science, and strengthen the nation’s research community to accelerate commercialization.

The Quantum Systems Accelerator will optimize a wide range of advanced qubit technologies available today. Berkeley Lab uses sophisticated dilution refrigerators to cool and operate superconducting quantum processor circuits. (Credit: Thor Swift/Berkeley Lab.)

The Department of Energy (DOE) has awarded $115 million over five years to the Quantum Systems Accelerator (QSA), a new research center led by Lawrence Berkeley National Laboratory (Berkeley Lab) that will forge the technological solutions needed to harness quantum information science for discoveries that benefit the world. It will also energize the nation’s research community to ensure U.S. leadership in quantum R&D and accelerate the transfer of quantum technologies from the lab to the marketplace. Sandia National Laboratories is the lead partner of the center.

Total planned funding for the center is $115 million over five years, with $15 million in Fiscal Year 2020 dollars and outyear funding contingent on congressional appropriations. The center is one of five new Department of Energy Quantum Information Science (QIS) Research Centers.

The Quantum Systems Accelerator brings together dozens of scientists who are pioneers of many of today’s quantum capabilities from 15 institutions: Lawrence Berkeley National Laboratory, Sandia National Laboratories, University of Colorado at Boulder, MIT Lincoln Laboratory, Caltech, Duke University, Harvard University, Massachusetts Institute of Technology, Tufts University, UC Berkeley, University of Maryland, University of New Mexico, University of Southern California, UT Austin, and Canada’s Université de Sherbrooke.

“The global race is on to build quantum systems that fuel discovery and make possible the next generation of information technology that greatly improves our lives,” said Berkeley Lab’s Irfan Siddiqi, the director of the Quantum Systems Accelerator. “The Quantum Systems Accelerator will transform the enormous promise of quantum entanglement into an engineering resource for the nation, forging the industries of tomorrow.”

The center’s multidisciplinary expertise and network of world-class research facilities will enable the team to co-design the solutions needed to build working quantum systems that outperform today’s computers. The goal is to deliver prototype quantum systems that are optimized for major advances in scientific computing, discoveries in fundamental physics, and breakthroughs in materials and chemistry. In addition to furthering research that is critical to DOE’s missions, this foundational work will give industry partners a toolset to expedite the development of commercial technologies.

The Quantum Systems Accelerator will strengthen the nation’s quantum research ecosystem and help ensure its international leadership in quantum R&D by building a network of national labs, industry, and universities that addresses a broad spectrum of technological challenges. The center will train the workforce needed to keep the nation at the forefront of quantum information science, share its advances with the scientific community, and serve as a central clearinghouse for promising research.

“The national labs have repeatedly demonstrated the ability to accelerate progress by organizing teams of great scientists from several fields. With the Quantum Systems Accelerator we are bringing this tradition to advancing quantum technologies for the nation,” said Berkeley Lab director Mike Witherell.

Accelerating the development of quantum systems for science

A semiconductor chip ion trap, fabricated by Sandia National Laboratories and used in research at the University of Maryland, composed of gold-plated electrodes that suspend individual atomic ion qubits above the surface of the bow-tie shaped chip. (Credit: Chris Monroe/Duke University.)

Quantum mechanics predicts that matter, at the smallest of scales, can be correlated to a degree that is not naturally observed in everyday life. Reliably controlling this coherence in quantum bits, or qubits, could lead to quantum computers that perform calculations and solve urgent scientific challenges that are far beyond the reach of today’s computers. Quantum devices have the potential to significantly improve machine learning and optimization, transform the design of solar cells, new materials, and pharmaceuticals, and probe the mysteries of physics and the universe, among many other applications.

To bring this closer to reality, the Quantum Systems Accelerator will systematically improve a wide range of advanced qubit technologies available today, including neutral atom arrays, trapped ions, and superconducting circuits. The center will engineer new ways to control these platforms and improve their quantum coherence and qubit connectivity. In addition, QSA scientists will develop algorithms that are ideally suited to these platforms, using a co-design approach, enabling a new generation of hardware and software to solve scientific problems.

“The QSA combines Sandia’s expertise in quantum fabrication, engineering, and systems integration with Berkeley Lab’s lead capabilities in quantum theory, design, and development, and a team dedicated to meaningful impact for the emerging U.S. quantum industry,” said Sandia National Laboratories’ Rick Muller, deputy director of the Quantum Systems Accelerator.

“The quantum processors developed by the QSA will explore the mysterious properties of complex quantum systems in ways never before possible, opening unprecedented opportunities for scientific discovery while also posing new challenges,” said John Preskill, the Richard P. Feynman Professor of Theoretical Physics at Caltech and the QSA Scientific Coordinator.

Catalyzing the quantum research ecosystem and workforce

In addition to its core team, the Quantum Systems Accelerator will engage with more than 30 partners across academia, government labs, international research programs, and industry, including large companies and startups. These partnerships will enable the QSA to determine what’s needed to accelerate quantum R&D, and develop technology roadmaps that shepherd promising technologies from the lab to the factory.

To cultivate the future workforce of quantum scientists, engineers, and technicians, the center will partner with California and other states, community colleges, workforce boards, and industry to establish curricula for educators and create apprenticeship opportunities for people interested in quantum science, including women and under-represented minorities. The center will develop a QSA portal, a “one-stop quantum shop” that assembles resources for students and professionals eager to contribute to the future of quantum research.

“It’s imperative to build a quantum-ready workforce by strengthening connections among industry and educational institutions and by exposing students to industry internships and other experiences. The Quantum Economic Development Consortium (QED-C) is pleased to work with QSA to deliver on these goals,” said Celia Merzbacher, deputy director of the QED-C and a QSA external advisory board member.

See the full article here .

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LBNL Molecular Foundry

Bringing Science Solutions to the World
In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

A U.S. Department of Energy National Laboratory Operated by the University of California.

From Science Magazine: “Quantum paradox points to shaky foundations of reality”

From Science Magazine

Aug. 17, 2020
George Musser

Not just “philosophical mumbo-jumbo”: An experiment shows how facts may depend on the observer.
Davide Bonazzi/Salzman Art.

Nearly 60 years ago, the Nobel Prize–winning physicist Eugene Wigner captured one of the many oddities of quantum mechanics in a thought experiment. He imagined a friend of his, sealed in a lab, measuring a particle such as an atom while Wigner stood outside. Quantum mechanics famously allows particles to occupy many locations at once—a so-called superposition—but the friend’s observation “collapses” the particle to just one spot. Yet for Wigner, the superposition remains: The collapse occurs only when he makes a measurement sometime later. Worse, Wigner also sees the friend in a superposition. Their experiences directly conflict.

Now, researchers in Australia and Taiwan offer perhaps the sharpest demonstration that Wigner’s paradox is real. In a study published this week in Nature Physics, they transform the thought experiment into a mathematical theorem that confirms the irreconcilable contradiction at the heart of the scenario. The team also tests the theorem with an experiment, using photons as proxies for the humans. Whereas Wigner believed resolving the paradox requires quantum mechanics to break down for large systems such as human observers, some of the new study’s authors believe something just as fundamental is on thin ice: objectivity. It could mean there is no such thing as an absolute fact, one that is as true for me as it is for you.

“It’s a bit disconcerting,” says co-author Nora Tischler of Griffith University. “A measurement outcome is what science is based on. If somehow that’s not absolute, it’s hard to imagine.”

For physicists who have dismissed thought experiments like Wigner’s as interpretive navel gazing, the study shows the contradictions can emerge in actual experiments, says Dustin Lazarovici, a physicist and philosopher at the University of Lausanne who was not part of the team. “The paper goes to great lengths to speak the language of those who have tried to merely discuss foundational issues away and may thus compel at least some to face up to them,” he says.

Wigner’s thought experiment has seen renewed attention in recent years. In 2015, Časlav Brukner of the University of Vienna tested the most intuitive way around the paradox: that the friend inside the lab has, in fact, seen the particle in one place or another, and Wigner just doesn’t know what it is yet. In the jargon of quantum theory, the friend’s result is a hidden variable.

Brukner ruled out that conclusion in a thought experiment of his own, using a trick—based on quantum entanglement—to bring the hidden variable out into the open. He imagined setting up two friend-Wigner pairs and giving each a particle, entangled with its partner in such a way that their attributes, upon measurement, are correlated. Each friend measures the particle, each Wigner measures the friend measuring the particle, and the two Wigners compare notes. The process repeats. If the friends saw definite results—as you might suspect—the Wigners’ own findings would show only weak correlations. But instead, they find a pattern of strong correlations. “You run into contradictions,” Brukner says. His experiment and a similar one in 2016 by Daniela Frauchiger and Renato Renner of ETH Zürich led to an outpouring of papers and heated discussion at conferences.

But in 2018, Richard Healey, a philosopher of physics at the University of Arizona, pointed out a loophole in Brukner’s thought experiment, which Tischler and her colleagues have now closed. In their new scenario they make four assumptions. One is that the results the friends obtain are real: They can be combined with other measurements to form a shared corpus of knowledge. They also assume quantum mechanics is universal, and as valid for observers as for particles; that the choices the observers make are free of peculiar biases induced by a godlike superdeterminism; and that physics is local, free of all but the most limited form of “spooky action” at a distance.

Yet their analysis shows the contradictions of Wigner’s paradox persist. The team’s tabletop experiment, in which they created entangled photons, also backs up the paradox. Optical elements steered each photon onto a path that depended on its polarization: the equivalent of the friends’ observations. The photon then entered a second set of elements and detectors that played the role of the Wigners. The team found, again, an irreconcilable mismatch between the friends and the Wigners. What is more, they varied exactly how entangled the particles were and showed that the mismatch occurs for different conditions than in Brukner’s scenario. “That shows that we really have something new here,” Tischler says.

It also indicates that one of the four assumptions has to give. Few physicists believe superdeterminism could be to blame. Some see locality as the weak point, but its failure would be stark: One observer’s actions would affect another’s results even across great distances—a stronger kind of nonlocality than the type quantum theorists often consider. So some are questioning the tenet that observers can pool their measurements empirically. “It could be that there are facts for one observer, and facts for another; they need not mesh,” says study co-author and Griffith physicist Howard Wiseman. It is a radical relativism, still jarring to many. “From a classical perspective, what everyone sees is considered objective, independent of what anyone else sees,” says Olimpia Lombardi, a philosopher of physics at the University of Buenos Aires.

And then there is Wigner’s conclusion that quantum mechanics itself breaks down. Of the assumptions, it is the most directly testable, by experiments that are probing quantum mechanics on ever larger scales. But the one position that doesn’t survive the analysis is to have no position, says another co-author at Griffith, Eric Cavalcanti. “Most physicists, they think: ‘That’s just philosophical mumbo-jumbo,’” he says. “They will have a hard time.”

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