In the same way that cream blends into coffee, transforming it from a whirl of white to a uniform brown, quantum computer chips face a challenge.

These devices operate on the minuscule scale of the universes fundamental particles, where data can quickly become chaotic, limiting memory efficiency.

However, new research spearheaded by Rahul Nandkishore, an associate professor of physics at the University of Colorado Boulder, suggests a groundbreaking approach that could revolutionize data retention in quantum computing.

Nandkishore and his team, through mathematical modeling, propose a scenario akin to cream and coffee that never mix, regardless of how much they are stirred.

This concept, if realized, could lead to significant advancements in quantum computer chips, providing engineers with novel methods for storing data in extremely small scales.

Nandkishore, the senior author of the study, illustrates his idea using the familiar sight of cream swirling in coffee, imagining these patterns remaining dynamic indefinitely.

Think of the initial swirling patterns that appear when you add cream to your morning coffee, said Nandkishore. Imagine if these patterns continued to swirl and dance no matter how long you watched.

This concept is central to the study, which involved David Stephen and Oliver Hart, postdoctoral researchers in physics at CU Boulder.

Quantum computers differ fundamentally from classical computers. While the latter operate on bits (zeros or ones), quantum computers use qubits, which can exist as zero, one, or both simultaneously.

Despite their potential, qubits can easily become disordered, leading to a loss of coherent data, much like the inevitable blending of cream into coffee.

Nandkishore and his teams solution lies in arranging qubits in specific patterns that maintain their information even under disturbances, like magnetic fields.

This could be a way of storing information, he said. You would write information into these patterns, and the information couldnt be degraded.

This arrangement could allow for the creation of devices with quantum memory, where data, once written into these patterns, remains uncorrupted.

The researchers employed mathematical models to envision an array of hundreds to thousands of qubits in a checkerboard pattern.

They discovered that tightly packing qubits influences their neighboring qubits behavior, akin to a crowded phone booth where movement is severely limited.

This specific arrangement might enable the patterns to flow around a quantum chip without degrading, much like the enduring swirls of cream in a cup of coffee.

Nandkishore notes that this studys implications extend beyond quantum computing.

The wonderful thing about this study is that we discovered that we could understand this fundamental phenomenon through what is almost simple geometry, Nandkishore said.

It challenges the common understanding that everything in the universe, from coffee to oceans, moves toward thermal equilibrium, where differences in temperature eventually even out, like ice melting in a warm drink.

His findings suggest that certain matter organizations might resist this equilibrium, potentially defying some long-standing physical laws.

While further experimentation is necessary to validate these theoretical swirls, the study represents a significant stride in the quest to create materials that stay out of equilibrium for extended periods.

This pursuit, known as ergodicity breaking, could redefine our understanding of statistical physics and its application to everyday phenomena.

As Nandkishore puts it, while we wont need to rewrite the math for ice and water, there are scenarios where traditional statistical physics might not apply, opening new frontiers in quantum computing and beyond.

The full study was published in the journal Physical Review Letters.

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Coffee, creamer, and the Quantum Realm - Earth.com

By Light Publishing Center, Changchun Institute of Optics, Fine Mechanics And Physics, CAS January 25, 2024

New research reveals new insights into electron tunneling dynamics at the sub-nanometer scale. Using a van der Waals complex, Ar-Kr+, and an innovative approach for tracking tunneling dynamics, the research highlights the crucial influence of neighboring atoms in quantum tunneling. This work has important implications for quantum physics, nanoelectronics, and the study of complex biomolecules.

Tunneling is a fundamental process in quantum mechanics, involving the ability of a wave packet to cross an energy barrier that would be impossible to overcome by classical means. At the atomic level, this tunneling phenomenon significantly influences molecular biology. It aids in speeding up enzyme reactions, causes spontaneous DNA mutations, and initiates the sequences of events that lead to the sense of smell.

Photoelectron tunneling is a key process in light-induced chemical reactions, charge and energy transfer, and radiation emission. The size of optoelectronic chips and other devices has been close to the sub-nanometer atomic scale, and the quantum tunneling effects between different channels would be significantly enhanced.

The electronic chip and the Van der Waals complex with an internuclear distance 0.39 nm. Credit: Ming Zhu, Jihong Tong, Xiwang Liu, Weifeng Yang, Xiaochun Gong, Wenyu Jiang, Peifen Lu, Hui Li, Xiaohong Song & Jian Wu

The real-time imaging of electron tunneling dynamics in complex has important scientific significance for promoting the development of tunneling transistors and ultrafast optoelectronic devices. The effect of neighboring atoms on electron tunneling dynamics in the complex is one of the key scientific issues in the fields of quantum physics, quantum chemistry, nanoelectronics, etc.

In a new paper published in Light Science & Application, a team of scientists from Hainan University and East China Normal University designed a van der Waals complex Ar-Kr+ as a prototype system with an internuclear distance of 0.39 nm to track the electron tunneling via the neighboring atom in the system of sub-nanometer scale.

The electron emitted from Ar atom is firstly trapped to the highly excited transient states of the Ar-Kr+* before its eventual release to the continuum. A linearly polarized pump laser pulse is used to prepare the Ar-Kr+ ion by removing e1 from Kr site, and a time-delayed elliptically polarized probe laser pulse is used to track the electron transfer mediated electron tunneling dynamics (e2, orange arrow). Credit: Ming Zhu, Jihong Tong, Xiwang Liu, Weifeng Yang, Xiaochun Gong, Wenyu Jiang, Peifen Lu, Hui Li, Xiaohong Song & Jian Wu

The intrinsic electron localization of the highest occupied molecular orbital of Ar-Kr gives a preference for electron removal from the Kr site in the first ionization step. The site-assisted electron-hole in Ar-Kr+ guarantees that the second electron is mainly removed from the Ar atom in the second ionization step, where the electron may straightly tunnel to the continuum from the Ar atom or alternatively via the neighboring Kr+ ionic core.

In combination with the improved Coulomb-corrected strong-field approximation (ICCSFA) method developed by the team, which is able to take into account the Coulomb interaction under the potential during tunneling, and by monitoring the photoelectron transverse momentum distribution to track the tunneling dynamics, then, it was discovered that there are two effects of strong capture and weak capture of tunneling electrons by a neighboring atom.

This work successfully reveals the critical role of neighboring atoms in electron tunneling in sub-nanometer complex systems. This discovery provides a new way to deeply understand the key role of the Coulomb effect under the potential barrier in the electron tunneling dynamics, solid high harmonics generation, and lays a solid research foundation for probing and controlling the tunneling dynamics of complex biomolecules.

Reference: Tunnelling of electrons via the neighboring atom by Ming Zhu, Jihong Tong, Xiwang Liu, Weifeng Yang, Xiaochun Gong, Wenyu Jiang, Peifen Lu, Hui Li, Xiaohong Song and Jian Wu, 16 January 2024, Light: Science & Applications.DOI: 10.1038/s41377-023-01373-2

The study was funded by the National Natural Science Foundation of China, the Hainan Provincial Natural Science Foundation of China, Fundamental Research Funds for the Central Universities, and the Sino-German Center for Research Promotion.

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Quantum Breakthrough: Unveiling the Mysteries of Electron Tunneling - SciTechDaily

BOULDER, Colo. Your morning coffee is playing an important role in the world of quantum physics. Adding cream to a cup of joe can cause mesmerizing swirls, but imagine if it was for an indefinite period of time instead of a few seconds. Researchers at the University of Colorado-Boulder are now drawing a parallel between this tasty event and the potential advancements of quantum computing.

They have made a theoretical breakthrough, suggesting that quantum computer chips could be engineered to maintain information in a constant state, much like unending swirls in a coffee cup. This discovery could revolutionize how we approach data storage in quantum computers.

What Are Quantum Computers?

Quantum computers, unlike traditional computers, operate on qubits instead of bits. While bits represent data as zeros or ones, qubits, due to the peculiarities of quantum physics, can exist as zero, one, or both simultaneously. This unique capability allows quantum computers to perform complex computations at unprecedented speeds. However, qubits are notoriously susceptible to becoming jumbled, leading to disorganized and unusable data a challenge akin to the settling of coffee swirls into a uniform brown liquid.

Scientists have proposed a solution to this instability. By arranging qubits in specific patterns, similar to a checkerboard, and bringing them in close proximity, they can influence each other in a way that preserves their initial state. This arrangement, the researchers suggest, could create a form of quantum memory, resistant to disturbances like magnetic fields.

This could be a way of storing information, says study author Rahul Nandkishore, an associate professor of physics at CU Boulder, in a university release. You would write information into these patterns, and the information couldnt be degraded.

The study used mathematical models to envision an array of hundreds to thousands of qubits in tight configurations. In such a setup, individual qubits can affect their neighbors, preventing them from flipping states randomly. This concept, Nandkishore explains, is akin to squeezing people into a telephone booth, where movement is highly restricted.

Beyond quantum computers, this research touches on fundamental principles of physics. It challenges the concept of thermal equilibrium, where systems like a cup of coffee or an ice cube in water eventually reach a uniform state. Nandkishores work suggests that in certain conditions, systems can resist this equilibrium, potentially defying long-standing physical laws.

The wonderful thing about this study is that we discovered that we could understand this fundamental phenomenon through what is almost simple geometry, says Nandkishore.

While further experimental validation is required, the research teams findings offer a promising avenue for developing more stable and efficient quantum computers, potentially leading to significant advancements in the field.

Were not going to have to redo our math for ice and water, concludes Nandkishore. The field of mathematics that we call statistical physics is incredibly successful for describing things we encounter in everyday life. But there are settings where maybe it doesnt apply.

The study is published in the journal Physical Review Letters.

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Coffee With Cream Is Revolutionizing Quantum Physics - Study Finds

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Electrons that spin to the right and the left at the same time. Particles that change their states together, even though they are separated by enormous distances. Intriguing phenomena like these are completely commonplace in the world of quantum physics. Researchers at the TUM Garching campus are using them to build quantum computers, high-sensitivity sensors and the internet of the future.

"We cool the chip down to only a few thousandths of a degree above absolute zerocolder than in outer space," says Rudolf Gross, Professor of Technical Physics and Scientific Director of the Walther Meissner Institute (WMI) at the Garching research campus. He's standing in front of a delicate-looking device with gold-colored disks connected by cables: The cooling system for a special chip that utilizes the bizarre laws of quantum physics.

For about twenty years now, researchers at WMI have been working on quantum computers, a technology based on a scientific revolution that occurred 100 years ago when quantum physics introduced a new way of looking at physics. Today it serves as the foundation for a "new era of technology," as Prof. Gross calls it.

To shape this emerging era, researchers at Garching are investigating ways to utilize the rules of quantum physics, as well as the associated risks and the potential benefits of quantum technology to society.

"We encounter quantum physics every day," says Gross. For example, when we see a stovetop burner element glowing red. In 1900 Max Planck found the formula for the radiation that bodies of different temperatures emit. This meant that he had to assume that the emitted light consists of tiny energy parcels, referred to as quanta. Quantum physics continued to develop in the years that followed, fundamentally changing our understanding of the microcosmos. New technologies exploited the special properties of atoms and electrons, for example, the laser, the magnetic resonance tomograph and the computer chip.

The technologies of this first quantum revolution control large quantities of particles. In the meantime, physicists can also manipulate individual atoms and photons and can produce objects that obey the laws of quantum physics. "Today we can create tailor-made quantum systems," says Gross. The principles of quantum physics, for which there as yet hardly any technological realizations, can be used in this so-called second quantum revolution.

The first of these principles is superposition: A quantum object can assume parallel states, which are mutually exclusive in the classic frame of reference. For example, an electron can rotate both to the right and to the left at the same time. The superposed states can also mutually interact, similar to intersecting waves which either reinforce one another or cancel out one anotherthis is the second principle: Quantum interference.

The third phenomenon is entanglement. Two particles can have a joint quantum state, even if they are located kilometers away from one another. For example, if we measure the polarization of a given photon, then the measurement result for the entangled partner is instantaneously ascertained as if the space between the two photons did not exist.

As exotic as these concepts may sound, they're equally important for technical progress. Classical computers have a drawback: They process information sequentially, one step at a time. "Not even supercomputers which are constantly growing faster will be able to master all the tasks at hand," says Gross, since the complexity of some tasks can increase drastically.

For example, the number of possible travel routes between several cities increases with each potential stop. There are six possible routes between four cities, while for 15 cities the number is more than 40 billion. Thus, the task of finding the shortest route very quickly becomes overwhelmingly complex, even unsolvable, using classical computers within a viable amount of time.

The principle of superposition makes the task much easier for the quantum computer: It uses quantum bits, or qubits, which can process the bit values 0 and 1 simultaneously instead of sequentially. A large number of qubits, linked with one another by quantum interference or entanglement, can process an inconceivably large number of combinations in parallel and can thus solve highly complex tasks very quickly.

Back to WMI: Here we find silver vacuum chambers in which metal atoms are precisely deposited on hand-sized silicon wafers. The highly pure metal layers forming on these wafers form the basis for tiny circuits. When supercooling makes the circuits superconductive, the electricity they carry oscillates at various frequencies corresponding to different energy levels. The two lowest levels serve as the qubit values 0 and 1. The chip in one of these cooling systems contains six qubits, sufficient for research purposes.

However, quantum computers need several hundred qubits in order to solve practical problems. In addition, each one of the qubits should be able to perform as many computational steps as possible in order to realize algorithms that are relevant for practical purposes. But qubits lose their superposition very quickly, even after the slightest disturbance, such as material defects or electrosmog"an enormous problem," says Gross.

Complex correction procedures must then be used to correct these errors, but these processes will require thousands of additional qubits. Experts expect that this will take many years to achieve. Nevertheless, initial applications could already be functional when the number of qubit errors is reduced, if not eliminated.

"One important error source is unwanted mutual interaction between qubits," says Dr. Kirill Fedorov of the WMI. His remedy: Distributing qubits across several chips and entangling them with one another. In the basement of the WMI Fedorov points to a tube with the diameter of a tree branch leading from one quantum computer to the next. The tubes contain microwave conductors which put the qubits into mutual interaction with one another. This approach could make it possible for thousands of qubits to work together in the future.

Eva Weig, Professor of Nano and Quantum Sensor Technology, has a different perspective on this lack of perfection. "The fact that quantum states react so sensitively to everything can also be an advantage," she says. Even the most minute magnetic fields, pressure variations or temperature fluctuations can measurably change a quantum state. "This can make sensors more sensitive and more precise and make them capable of better spatial resolution," says Weig.

She wants to use relatively large objects as mechanical quantum sensors. Even nanostructures consisting of millions of atoms can be put into their quantum ground state, as researchers at the University of California first demonstrated in 2010. Eva Weig is building on the finding. "I want to construct easily controlled nanosystems in order to measure the smallest forces."

In the laboratory, the physicist presents a chip her team made in its own cleanroom. On it are what she calls "nano-guitars," invisible to the naked eye: Tiny strings, 1,000 times thinner than a human hair, which vibrate at radio frequency. Weig's team is attempting to put these nano-oscillators into a defined quantum state. Then the strings could be used as quantum sensors, for example in measuring the forces existing between individual cells.

Professor of Quantum Networks Andreas Reiserer wants to use another aspect of quantum systems in order to facilitate a quantum internet: The quantum state of a particle is destroyed when it is measured, meaning that the information it contains can only be read out once. Thus any attempt at interception would inevitably leave behind traces. If there are no such traces, a communication can then be trusted. "Quantum cryptography is cost-effective and can already support interception-proof communication today," he says.

But the scope of this technology still remains limited. According to Reiserer, fiber optic elements are ideal for transporting quantum information using light. But the glass absorbs some of the light in every kilometer it travels. After about 100 kilometers, communication is no longer possible.

Reiserer's team is therefore conducting research into what are called quantum repeaters, storage units for quantum information which are to be spaced out along the fiber optical network approximately every 100 kilometers. If it is possible to entangle each of the quantum repeaters with its immediate neighbor, then information sent can be passed on without any loss. "This way we hope to be able to traverse global-scale distances," Reiserer says. "Then it could be possible to link devices everywhere around the world to form a 'quantum supercomputer.'"

The Munich-based team wants to miniaturize quantum repeaters, to simplify them and make them suitable for mass production by putting them onto a computer chip. The chip contains an optical fiber in which erbium atoms have been embedded. These atoms serve as qubits which can buffer the information. However, Reiserer admits, this requires cooling to as little as four degrees Kelvin (i.e., approximately -269C) and adds that a lot more research will be necessary before practical viability is achieved.

The arrival of quantum technologies in everyday life also entails some risks. An error-corrected quantum computer could crack today's conventional encryption procedures and could for example compromise online banking security. "The good news is that there are already new encryption procedures which are secure against quantum computer attacks," says Urs Gasser, Professor of Public Policy, Governance and Innovative Technology and head of the "Quantum Social Lab" at TUM. Gasser, a legal scholar, adds that the transition will take several years, making it necessary to get started now.

"The cost of arriving too late could even outstrip the cost of being late on Artificial Intelligence," Gasser warns. The Quantum Social Lab focuses on the ethical, legal and societal impacts of emerging quantum technologies. This includes for example the question of how to integrate people in the debate surrounding the new technology, or whether or not only wealthy countries should be able to better plan their cities thanks to quantum optimization.

"The second quantum revolution is a paradigm shift which will have a far-reaching social, political and economic impact," says Prof. Gasser. "We have to shape this revolution in the best interests of society."

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Shaping the dawn of the quantum age - Phys.org

Mickael Perrins pioneering work in quantum electronics focuses on generating electricity with minimal loss and improving energy efficiency in electronics, using groundbreaking applications of graphene nanoribbons. His research, recognized by prestigious awards, aims to revolutionize the practical application of quantum technologies. Credit: SciTechDaily.com

Quantum physicist Mickael Perrin uses graphene ribbons to build nanoscale power plants that turn waste heat from electrical equipment into electricity.

When Mickael Perrin started out on his scientific career 12 years ago, he had no way of knowing he was conducting research in an area that would be attracting wide public interest only a few years later: quantum electronics.

At the time, physicists were just starting to talk about the potential of quantum technologies and quantum computers, he recalls. Today there are dozens of start-ups in this area, and governments and companies are investing billions in developing the technology further. We are now seeing the first applications in computer science, cryptography, communications, and sensors.

Perrins research is opening up another field of application: electricity production using quantum effects with almost zero energy loss. To achieve this, the 36-year-old scientist combines two usually separate disciplines of physics: thermodynamics and quantum mechanics.

Mickael Perrin. Credit: SNF

In the past year, the quality of Perrins research and its potential for future applications has brought him two awards: he received not only one of the ERC Starting Grants that are so highly sought-after by young researchers, but also an Eccellenza Professorial Fellowship of the Swiss National Science Foundation (SNS)F. He now leads a research group of nine at Empa as well as being an Assistant Professor of Quantum Electronics at ETH Zurich.

Perrin tells us that he never regarded himself as having a natural gift for mathematics. It was mainly curiosity that pushed me in the direction of physics. I wanted to gain a better understanding of how the world around us works, and physics offers excellent tools for doing just that. After finishing high school in Amsterdam, he began a degree in applied physics at Delft University of Technology (TU Delft) in 2005. Right from the start, Perrin was more interested in concrete applications than theory.

It was while studying under Herre van der Zant, a pioneer in the field of quantum electronics, that Perrin first experienced the fascination of engineering tiny devices at microscale and nanoscale. He soon recognized the endless possibilities presented by molecular electronics, since circuits have completely different characteristics depending on the molecules and materials selected, and can be used as transistors, diodes, or sensors.

While studying for his doctorate, Perrin spent a great deal of time in the nanolab cleanroom at TU Delft constantly enveloped in a white full-body overall to prevent the miniature electronics from being contaminated by hairs or dust particles. The cleanroom provided the technological infrastructure to build machines a few nanometres in size (around 10,000 times smaller than the diameter of a human hair).

As a general rule, the smaller the structure you want to build, the bigger and more expensive the machine you will need to do so, explains Perrin. Lithography machines, for example, are used to pattern complex mini-circuits on microchips. Nanofabrication and experimental physics require a lot of creativity and patience, because something nearly always goes wrong, says Perrin. Yet its the strange and unexpected results that often turn out to be the most exciting.

A year after completing his doctorate, Perrin obtained a post at Empa in the laboratory of Michel Calame, an expert in integrating quantum materials into nano devices. Since then, Perrin a French and Swiss national has lived in Dbendorf with his partner and two daughters.

Switzerland was a good choice for me for several reasons, he says. The research infrastructure is unparalleled. Empa, ETH Zurich and the IBM Research Center in Rschlikon provide him with everything he needs in order to produce nanostructures, as well as the measuring instruments to test them.

Also, Im an outdoor type. I love the mountains, and often go walking and skiing with my family. Perrin is a keen rock climber, too. He sometimes takes himself off climbing in remote valleys for weeks at a time, often in France, which is his familys country of origin.

At Empa this young researcher had the freedom to continue experimenting with nanomaterials. A certain material soon attracted his particular attention: graphene nanoribbons, a material made from carbon atoms that is as thin as the individual atoms. These nanoribbons are manufactured with the greatest precision by Roman Fasels group at Empa. Perrin was able to show that these ribbons have unique properties and can be used for a whole raft of quantum technologies.

At the same time, he began to take a close interest in converting heat into electrical energy. In 2018 it was in fact proved that quantum effects can be used to efficiently convert thermal energy into electricity.

Up to now, the problem has been that these desirable physical properties appear only at very low temperatures close to absolute zero (0 Kelvin; -273C). This is of little relevance to potential future applications such as in smartphones or minisensors. Perrin had the idea of circumventing this problem by using graphene nanoribbons. Their specific physical properties mean that temperature has a much smaller impact on the quantum effects and thus the desired thermoelectric effects than is the case with other materials.

His group at Empa was soon able to demonstrate that the quantum effects of graphene nanoribbons are largely preserved even at 250 Kelvin, i.e. -23C. In the future, the system is expected to work at room temperature, too.

There are still many challenges to overcome before the technology will enable our smartphones to use less power. Extreme miniaturization means that special components keep being required to ensure that the built systems actually work.

Perrin, together with colleagues from China, the UK, and Switzerland, recently showed that carbon nanotubes just one nanometre in diameter can be integrated into those systems as electrodes. However, Perrin estimates that it will take at least another 15 years before these delicate and highly complicated materials can be manufactured at scale and incorporated in devices.

My aim is to work out the fundamental basis for applying this technology. Only then will we be able to gauge its potential for practical uses.

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Nanoscale Power Plants: Turning Heat Into Power With Graphene Ribbons - SciTechDaily