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Antiferromagnetically ordered particles are represented by red and blue spheres in this artist’s impression. The particles are in an array of optical traps. Credit: Chen Lei

Topics: Applied Physics, Computer Science, Quantum Computer, Quantum Mechanics

Experiments on the Fermi–Hubbard model can now be made much larger, more uniform, and more quantitative.

A universal quantum computer—capable of crunching the numbers of any complex problem posed to it—is still a work in progress. But for specific problems in quantum physics, there’s a more direct approach to quantum simulation: Design a system that captures the physics you want to study, and then watch what it does. One of the systems most widely studied that way is the Fermi–Hubbard model (FHM), in which spin-up and spin-down fermions can hop among discrete sites in a lattice. Originally conceived as a stripped-down description of electrons in a solid, the FHM has attracted attention for its possible connection to the mysterious physics of high-temperature superconductivity.

Stripped down, though it may be, the FHM defies solution, either analytical or numerical, except in the simplest cases, so researchers have taken to studying it experimentally. In 2017, Harvard University’s Markus Greiner and colleagues made a splash when they observed antiferromagnetic order—a checkerboard pattern of up and down spins—in their FHM experiment consisting of fermionic atoms in a 2D lattice of 80 optical traps. (See Physics Today, August 2017, page 17.) The high-temperature-superconductor phase diagram has an antiferromagnetic phase near the superconducting one, so the achievement promised more exciting results to come. But the small size of the experiment limited the observations the researchers could make.

A 10 000-fold leap for a quintessential quantum simulator, Johanna L. Miller, Physics Today.

Credit: CC0 Public Domain

Topics: Condensed Matter Physics, Materials Science, Quantum Computer, Quantum Mechanics

Quantum scientists have discovered a rare phenomenon that could hold the key to creating a 'perfect switch' in quantum devices, which flips between being an insulator and a superconductor.

The research, led by the University of Bristol and published in Science, found these two opposing electronic states exist within purple bronze, a unique one-dimensional metal composed of individual conducting chains of atoms.

Tiny changes in the material, for instance, prompted by a small stimulus like heat or light, may trigger an instant transition from an insulating state with zero conductivity to a superconductor with unlimited conductivity and vice versa. This polarized versatility, known as "emergent symmetry," has the potential to offer an ideal On/Off switch in future quantum technology developments.

Lead author Nigel Hussey, Professor of Physics at the University of Bristol, said, "It's a really exciting discovery that could provide a perfect switch for quantum devices of tomorrow.

"The remarkable journey started 13 years ago in my lab when two Ph.D. students, Xiaofeng Xu, and Nick Wakeham, measured the magnetoresistance—the change in resistance caused by a magnetic field—of purple bronze."

In the absence of a magnetic field, the resistance of purple bronze was highly dependent on the direction in which the electrical current was introduced. Its temperature dependence was also rather complicated. Around room temperature, the resistance is metallic, but as the temperature is lowered, this reverses and the material appears to be turning into an insulator. Then, at the lowest temperatures, the resistance plummets again as it transitions into a superconductor.

Despite this complexity, surprisingly, the magnetoresistance was found to be extremely simple. It was essentially the same irrespective of the direction in which the current or field was aligned and followed a perfect linear temperature dependence all the way from room temperature down to the superconducting transition temperature.

Research reveals rare metal could offer revolutionary switch for future quantum devices, Queen's University Belfast, Phys.org.

Topics: Chemistry, Computer Science, Quantum Computer, Quantum Mechanics

Scientists at the University of Sydney have, for the first time, used a quantum computer to engineer and directly observe a process critical in chemical reactions by slowing it down by a factor of 100 billion times.

Joint lead researcher and Ph.D. student Vanessa Olaya Agudelo said, "It is by understanding these basic processes inside and between molecules that we can open up a new world of possibilities in materials science, drug design, or solar energy harvesting.

"It could also help improve other processes that rely on molecules interacting with light, such as how smog is created or how the ozone layer is damaged."

Specifically, the research team witnessed the interference pattern of a single atom caused by a common geometric structure in chemistry called a "conical intersection."

Conical intersections are known throughout chemistry and are vital to rapid photochemical processes such as light harvesting in human vision or photosynthesis.

Chemists have tried to directly observe such geometric processes in chemical dynamics since the 1950s, but it is not feasible to observe them directly, given the extremely rapid timescales involved.

To get around this problem, quantum researchers in the School of Physics and the School of Chemistry created an experiment using a trapped-ion quantum computer in a completely new way. This allowed them to design and map this very complicated problem onto a relatively small quantum device—and then slow the process down by a factor of 100 billion. Their research findings are published August 28 in Nature Chemistry.

"In nature, the whole process is over within femtoseconds," said Olaya Agudelo from the School of Chemistry. "That's a billionth of a millionth—or one quadrillionth—of a second.

"Using our quantum computer, we built a system that allowed us to slow down the chemical dynamics from femtoseconds to milliseconds. This allowed us to make meaningful observations and measurements.

"This has never been done before."

Joint lead author Dr. Christophe Valahu from the School of Physics said, "Until now, we have been unable to directly observe the dynamics of 'geometric phase'; it happens too fast to probe experimentally.

"Using quantum technologies, we have addressed this problem."

Scientists use a quantum device to slow down simulated chemical reactions 100 billion times. University of Sydney, Phys.org.

Chip off the old block: Intel’s Tunnel Falls chip is based on silicon spin qubits, which are about a million times smaller than other qubit types. (Courtesy: Intel Corporation)

Topics: Applied Physics, Chemistry, Electrical Engineering, Quantum Computer, Quantum Mechanics

Intel – the world’s biggest computer-chip maker – has released its newest quantum chip and has begun shipping it to quantum scientists and engineers to use in their research. Dubbed Tunnel Falls, the chip contains a 12-qubit array and is based on silicon spin-qubit technology.

The distribution of the quantum chip to the quantum community is part of Intel’s plan to let researchers gain hands-on experience with the technology while at the same time enabling new quantum research.

The first quantum labs to get access to the chip include the University of Maryland, Sandia National Laboratories, the University of Rochester, and the University of Wisconsin-Madison.

The Tunnel Falls chip was fabricated on 300 mm silicon wafers in Intel’s “D1” transistor fabrication facility in Oregon, which can carry out extreme ultraviolet lithography (EUV) and gate and contact processing techniques.

Intel releases 12-qubit silicon quantum chip to the quantum community, Martijn Boerkamp, Physics World.

A quantum computer at IBM’s Thomas J. Watson Research Center.

Credit: Connie Zhou for IBM

Topics: Computer Science, Cryptography, Cybersecurity, Quantum Computer

A team of researchers in China has unveiled a technique that — theoretically — could crack the most commonly used types of digital privacy using a rudimentary quantum computer.

The technique worked in a small-scale demonstration, the researchers report, but other experts are skeptical that the procedure could scale up to beat ordinary computers at the task. Still, they Are quantum computers about to break online privacy. Davide Castelvecchi, Naturewarn that the paper, posted late last month on the arXiv repository¹, is a reminder of the vulnerability of online privacy.

Quantum computers are known to be a potential threat to current encryption systems. However, the technology is still in its infancy, and researchers typically estimate that it will be many years until it can be faster than ordinary computers at cracking cryptographic keys.

Researchers realized in the 1990s that quantum computers could exploit peculiarities of physics to perform tasks that seem to be beyond the reach of ‘classical’ computers. Peter Shor, a mathematician now at the Massachusetts Institute of Technology in Cambridge, showed in 1994² how to apply the phenomena of quantum superposition and interference to factoring integer numbers into primes — the integers that cannot be further divided without a remainder.

Are quantum computers about to break online privacy? Davide Castelvecchi, Nature

Credit: sakkmesterke/ Getty Images

Topics: Lasers, Modern Physics, Quantum Computer, Quantum Mechanics

Physicists have devised a mind-bending error-correction technique that could dramatically boost the performance of quantum computers.

When the ancient Incas wanted to archive tax and census records, they used a device made up of a number of strings called a quipu, which encoded the data in knots. Fast-forward several hundred years, and physicists are on their way to developing a far more sophisticated modern equivalent. Their “quipu” is a new phase of matter created within a quantum computer, their strings are atoms, and the knots are generated by patterns of laser pulses that effectively open up [a] second dimension of time.

This isn’t quite as incomprehensible as it first appears. The new phase is one of many within a family of so-called topological phases, which were first identified in the 1980s. These materials display order not on the basis of how their constituents are arranged—like the regular spacing of atoms in a crystal—but on their dynamic motions and interactions. Creating a new topological phase—that is, a new “phase of matter”—is as simple as applying novel combinations of electromagnetic fields and laser pulses to bring order or “symmetry” to the motions and states of a substance’s atoms. Such symmetries can exist in time rather than space, for example in induced repetitive motions. Time symmetries can be difficult to see directly but can be revealed mathematically by imagining the real-world material as a lower-dimensional projection from a hypothetical higher-dimensional space, similar to how a two-dimensional hologram is a lower-dimensional projection of a three-dimensional object. In the case of this newly created phase, which manifests in a strand of ions (electrically charged atoms), its symmetries can be discerned by considering it as a material that exists in higher-dimensional reality with two-time dimensions.

“It is very exciting to see this unusual phase of matter realized in an actual experiment, especially because the mathematical description is based on a theoretical ‘extra’ time dimension,” says team member Philipp Dumitrescu, who was at the Flatiron Institute in New York City when the experiments were carried out. A paper describing the work was published in Nature on July 20.

Opening a portal to an extra time dimension—even just a theoretical one—sounds thrilling, but it was not the physicists’ original plan. “We were very much motivated to see what new types of phases could be created,” says study co-author Andrew Potter, a quantum physicist at the University of British Columbia. Only after envisioning their proposed new phase did the team members realize it could help protect data being processed in quantum computers from errors.

New Phase of Matter Opens Portal to Extra Time Dimension, Zeeya Merali, Scientific American

Image Source: Link below

Topics: Particle Physics, Quantum Computer, Quantum Mechanics, Theoretical Physics

Flatland: “The book used the fictional two-dimensional world of Flatland to comment on the hierarchy of Victorian culture, but the novella’s more enduring contribution is its examination of dimensions.” Source: Wikipedia

After decades of exploration in nature’s smallest domains, physicists have finally found evidence that anyons exist. First predicted by theorists in the early 1980s, these particle-like objects only arise in realms confined to two dimensions, and then only under certain circumstances — like at temperatures near absolute zero and in the presence of a strong magnetic field.

Physicists are excited about anyons not only because their discovery confirms decades of theoretical work, but also for practical reasons. For example, Anyons are at the heart of an effort by Microsoft to build a working quantum computer.

This year brought two solid confirmations of the quasiparticles. The first arrived in April, in a paper featured on the cover of Science, from a group of researchers at the École Normale Supérieure in Paris. Using an approach proposed four years ago, physicists sent an electron gas through a teeny-tiny particle collider to tease out weird behaviors — especially fractional electric charges — that only arise if anyons are around. The second confirmation came in July when a group at Purdue University in Indiana used an experimental setup on an etched chip that screened out interactions that might obscure anyon behavior.

MIT physicist Frank Wilczek, who predicted and named anyons in the early 1980s, credits the first paper as the discovery but says the second lets the quasiparticles shine. “It’s gorgeous work that makes the field blossom,” he says. Anyons aren’t like ordinary elementary particles; scientists will never be able to isolate one from the system where it forms. They’re quasiparticles, which means they have measurable properties like a particle — such as a location, maybe even a mass — but they’re only observable as a result of the collective behavior of other, conventional particles. (Think of the intricate geometric shapes made by group behavior in nature, such as flocks of birds flying in formation or schools of fish swimming as one.)

The known universe contains only two varieties of elementary particles. One is the family of fermions, which includes electrons, as well as protons, neutrons, and the quarks that form them. Fermions keep to themselves: No two can exist in the same quantum state at the same time. If these particles didn’t have this property, all matter could simply collapse to a single point. It’s because of fermions that solid matter exists.

The rest of the particles in the universe are bosons, a group that includes particles like photons (the messengers of light and radiation) and gluons (which “glue” quarks together). Unlike fermions, two or more bosons can exist in the same state at the same time. They tend to clump together. It’s because of this clumping that we have lasers, which are streams of photons all occupying the same quantum state.

Physicists prove the existence of two-dimensional particles called 'anyons', Stephen Omes, Astronomy (December 2020)

Topics: Quantum Computer, Quantum Mechanics, Thermodynamics

In what could prove to be a momentous accomplishment for fundamental physics and quantum physics, scientists say they’ve finally figured out how to manufacture a scientific oddity called a time crystal.

Time crystals harness a quirk of physics in which they remain ever-changing yet dynamically stable. In other words, they don’t give off energy as they change conformation, making them an apparent violation of the natural law that all things gradually turn towards entropy and disorder.

Now, it seems like it’s possible for these things to exist, after all, Quanta Magazine reports. At least, that’s according to what a massive team of researchers from Stanford, Princeton, and elsewhere working with Google’s quantum computing labs claimed in preprint research shared online last week. Aside from being an incredible scientific discovery in abstract — time crystals represent a new, bizarre phase of matter — the discovery could have profound implications for the finicky world of quantum computing.

“The consequence is amazing: You evade the second law of thermodynamics,” study coauthor and Max Planck Institute for the Physics of Complex Systems director Roderich Moessner told Quanta.

Google Claims To Create Time Crystals Inside Quantum Computer, Dan Robitzski, Futurism

(Credit: Yurchanka Siarhei/Shutterstock)

Topics: Computer Science, Quantum Computer, Quantum Mechanics

Quantum technologies are already revolutionizing life on Earth. But they also have the potential to change the way we operate in space. With the U.S., China, and Europe all investing heavily in this area, these changes are likely to be with us sooner rather than later.

So how will space-based quantum technologies make a difference?

Now, we get an overview thanks to the work of Rainer Kaltenbaek at the Institute for Quantum Optics and Quantum Information, in Austria, and colleagues throughout Europe, who have mapped out the future in this area and set out the advances that space-based quantum technologies will make possible.

While quantum computing and quantum communication grab most of the headlines, Kaltenbaek and colleagues point out that other quantum technologies are set to have equally impressive impacts. Take, for example, atom interferometry with quantum sensors.

These devices can measure with unprecedented accuracy any change in motion of a satellite in orbit as it is buffeted by tiny variations in the Earth’s gravitational field. These changes are caused by factors such as the movement of cooler, higher-density water flows in the deep ocean, flooding, the movement of the continents, and ice flows.

The Future of Space-Based Quantum Technology, Discover/Physics arXiv

Splitting up: schematic of the electron beam splitter with the n side on the right and the p side on the left. (Courtesy: M Jo et al/Phys. Rev. Lett.)

Topics: Graphene, Interferometry, Nanotechnology, Quantum Computer

A graphene-based “beam splitter” for electronic currents has been built by researchers in France, South Korea, and Japan. Created by Preden Roulleau at the University of Paris and colleagues, the tunable device’s operation is directly comparable to that of an optical interferometer. The technology could soon enable allow electron interferometry to be used in nanotechnology and quantum computing.

An optical interferometer splits a beam of light in two, sending each beam along a different path before recombining the beams at a detector. The measured interference of the beams at the detector can be used to detect tiny differences in the lengths of the two paths. Recently, physicists have become interested in doing a similar thing with currents of electrons in solid-state devices, taking advantage of the fact that electrons behave like waves in the quantum world.

Graphene is a sheet of carbon just one atom thick and is widely considered to be the best material for realizing such “electron quantum optics”. Indeed, researchers have already used the material to make simple electron interferometers. Now, Roulleau’s team has created a fully adjustable electron beam splitter that could be used to build more sophisticated devices. It exploits the quantum Hall effect, whereby the application of a strong magnetic field perpendicular to a sheet of graphene will cause an electron current to flow around the edge of the sheet.

Graphene beam splitter gives electron quantum optics a boost, Sam Jarman, Physics World

Nanophotonic integration for simultaneously controlling a large number of quantum mechanical spins in nanodiamonds. (Image: P. Schrinner/AG Schuck)

Topics: Nanotechnology, Quantum Computer, Quantum Mechanics, Semiconductor Technology

(Nanowerk News) Physicists at Münster University have succeeded in fully integrating nanodiamonds into nanophotonic circuits and at the same time addressing several of these nanodiamonds optically. The study creates the basis for future applications in the field of quantum sensing schemes or quantum information processors.

The results have been published in the journal Nano Letters ("Integration of Diamond-Based Quantum Emitters with Nanophotonic Circuits").

Using modern nanotechnology, it is possible nowadays to produce structures that have feature sizes of just a few nanometers.

This world of the most minute particles – also known as quantum systems – makes possible a wide range of technological applications, in fields which include magnetic field sensing, information processing, secure communication, or ultra-precise timekeeping. The production of these microscopically small structures has progressed so far that they reach dimensions below the wavelength of light.

In this way, it is possible to break down hitherto existent boundaries in optics and utilize the quantum properties of light. In other words, nanophotonics represents a novel approach to quantum technologies.

Controlling fully integrated nanodiamonds, Westfälische Wilhelms-Universität Münster