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January 25, 2022 | Research News

Tug-of-War Unlocks Menagerie of Quantum Phases of Matter

Often when physicists study phases of matter they examine how a solid slab of metal or a cloud of gas changes as it gets hotter or colder. Sometimes the changes are routine—we’ve all boiled water to cook pasta and frozen it to chill our drinks. Other times the transformations are astonishing, like when certain metals get cold enough to become superconductors or a gas heats up and breaks apart into a glowing plasma soup. However, changing the temperature is only one way to transmute matter into different phases. Scientists also blast samples with strong electric or magnetic fields or place them in special chambers and dial up the pressure. In these experiments, researchers are hunting for a stark transition in a material’s behavior or a change in the way its atoms are organized. In a new paper published recently in the journal Physical Review Letters, Barkeshli and two colleagues continued this tradition of exploring how materials respond to their environment. But instead of looking for changes in conductivity or molecular structure, they focused on changes in a uniquely quantum property: entanglement, or the degree to which quantum particles give up their individuality and become correlated with each other.
Technical graphic composed of two white dots on a blue-green background. The left dot shows a gradient from black to light yellow. A dotted line forms a semicircle connecting the two black dots on the edge of the white dot. The right white dot is filled with a hexagonal grid. The hexagons git smaller the further they are from the center of the dot. Each vertex of the hexagons is a colored dot with the ones near a larger grey dot being purple and the rest fading to yellow the further away they are.
January 18, 2022 | Research News

Enhancing Simulations of Curved Space with Qubits

One of the mind-bending ideas that physicists and mathematicians have come up with is that space itself—not just objects in space—can be curved. When space curves (as happens dramatically near a black hole), sizes and directions defy normal intuition. Understanding curved spaces is important to expanding our knowledge of the universe, but it is fiendishly difficult to study curved spaces in a lab setting (even using simulations). A previous collaboration between researchers at JQI explored using labyrinthine circuits made of superconducting resonators to simulate the physics of certain curved spaces. In particular, the team looked at hyperbolic lattices that represent spaces—called negatively curved spaces—that have more space than can fit in our everyday “flat” space. Our three-dimensional world doesn’t even have enough space for a two-dimensional negatively curved space. Now, in a paper published in the journal Physical Review Letters on Jan. 3, 2022, the same collaboration between the groups of JQI Fellows Alicia Kollár and Alexey Gorshkov, who is also Fellow of the Joint Center for Quantum Information and Computer Science, expands the potential applications of the technique to include simulating more intricate physics. They’ve laid a theoretical framework for adding qubits—the basic building blocks of quantum computers—to serve as matter in a curved space made of a circuit full of flowing microwaves. Specifically, they considered the addition of qubits that change between two quantum states when they absorb or release a microwave photon—an individual quantum particle of the microwaves that course through the circuit. 
Jay Sau sets in an office in front of a picture frame and framed artistic representation of the Latin alphabet.
January 14, 2022 | People News

Sau Named UMD Co-Director of JQI

JQI Fellow Jay Sau has been appointed the newest UMD Co-Director of JQI. He assumed the role on January 1, 2022.
An artist's depiction of an array of atomic ions controlled by lasers
December 20, 2021 | Research News

In a Smooth Move, Ions Ditch Disorder and Keep Their Memories

Scientists have found a new way to create disturbances that do not fade away. Instead of relying on disorder to freeze things in place, they tipped a quantum container to one side—a trick that is easier to conjure in the lab. A collaboration between the experimental group of College Park Professor Christopher Monroe and the theoretical group of JQI Fellow Alexey Gorshkov, who is also a Fellow of the Joint Center for Quantum Information and Computer Science, has used trapped ions to implement this new technique, confirming that it prevents their quantum particles from reaching equilibrium. The team also measured the slowed spread of information with the new tipping technique for the first time. They published their results recently in the journal Nature.
November 19, 2021 | People News

Two JQI Fellows Named 2021 Highly Cited Researchers

Two JQI Fellows are included on the Clarivate Web of Science Group’s 2021 list of Highly Cited Researchers, which recognizes influential scientists for their highly cited papers over the preceding decade. The two researchers are Sankar Das Sarma, who is also the Director of the Condensed Matter Theory Center and the Richard E. Prange Chair and Distinguished University Professor of Physics at the University of Marlyand (UMD), and Christopher Monroe, who is also a College Park Professor.
Two hexagonal grids are twisted relative to each other to create hexagonal snowflake-like repeating patterns against a blue background.
October 18, 2021 | Research News

Graphene’s Magic Act Relies on a Small Twist

Atomically thin sheets of carbon, called graphene, have caught many scientists' attention in recent years. Researchers have discovered that stacking layers of graphene two or three at a time and twisting the layers opens fertile new territory for them to explore. Research into these stacked sheets of graphene is like the Wild West, complete with the lure of striking gold and the uncertainty of uncharted territory. Researchers at JQI and the Condensed Matter Theory Center (CMTC) at the University of Maryland are busy creating the theoretical physics foundation that will be a map of this new landscape. And there is a lot to map; the phenomena in graphene range from the familiar like magnetism to more exotic things like strange metallicity, different versions of the quantum Hall effect, and the Pomeranchuk effect—each of which involve electrons coordinating to produce unique behaviors. One of the most promising veins for scientific treasure is the appearance of superconductivity (lossless electrical flow) in stacked graphene.
October 15, 2021 | People News

Hafezi Elected APS Fellow

JQI Fellow Mohammad Hafezi has been elected as a Fellow of the American Physical Society (APS). He was cited for “pioneering theoretical and experimental work in topological photonics and quantum synthetic matter.”
Photo of a diamond chip NV experiment
October 11, 2021 | Podcast | Research News

Diamonds Are a Quantum Sensing Scientist’s Best Friend

We all know that diamonds can hold great sentimental (and monetary) value. As luck may have it, diamonds—particularly defective ones, with little errors in their crystal structure—also hold great scientific value. The defects have properties that can only be described by quantum mechanics, and researchers are working on harnessing these properties to pick up on tiny signals coming from individual biological cells. In this episode of Relatively Certain, Dina sits down with defective diamond expert Ronald Walsworth, the founding director of the Quantum Technology Center at the University of Maryland (UMD), as well as Minta Martin professor of electrical and computer engineering and professor of physics at the UMD. Walsworth is also a member of the Institute for Research in Electronics & Applied Physics and a Fellow of the Joint Quantum Institute. Walsworth explains how diamond defects can be used as superb magnetic field sensors and discusses recent strides toward using them to image the insides of individual cells. More details on these advances can be found in two recent publications from Walsworth’s lab. This episode of Relatively Certain was produced by Dina Genkina, Chris Cesare and Emily Edwards. Music featured in this episode includes Picturebook by Dave Depper, The Jitters and Apogee by Metre and Examples by Ketsa, with sound effects by Brian Little. Relatively Certain is a production of the Joint Quantum Institute, a research partnership between the University of Maryland and the National Institute of Standards and Technology, and you can find it on iTunes, Google Play, Soundcloud or Spotify.
A chip made of golden bow-tie-shaped structure on top of a dark rectangular base that is used to contain ions for experiments and quantum computing tasks. The base of the chip has illegible markings on it.
October 4, 2021 | Research News

Foundational Step Shows Quantum Computers Can Be Better Than the Sum of Their Parts

Pobody’s nerfect—not even the indifferent, calculating bits that are the foundation of computers. But JQI Fellow Christopher Monroe’s group, together with colleagues from Duke University, have made progress toward ensuring we can trust the results of quantum computers even when they are built from pieces that sometimes fail. They have shown in an experiment, for the first time, that an assembly of quantum computing pieces can be better than the worst parts used to make it. In a paper published in the journal Nature on Oct. 4, 2021, the team shared how they took this landmark step toward reliable, practical quantum computers. In their experiment, the researchers combined several qubits—the quantum version of bits—so that they functioned together as a single unit called a logical qubit. They created the logical qubit based on a quantum error correction code so that, unlike for the individual physical qubits, errors can be easily detected and corrected, and they made it to be fault-tolerant—capable of containing errors to minimize their negative effects. This is the first time that a logical qubit has been shown to be more reliable than the most error-prone step required to make it.  
Rendering of a light-guiding lattice of micro-rings that researchers predict will create a highly efficient frequency comb
September 27, 2021 | Research News

Novel Design May Boost Efficiency of On-Chip Frequency Combs

On the cover of the Pink Floyd album Dark Side of the Moon, a prism splits a ray of light into all the colors of the rainbow. This multicolored medley, which owes its emergence to the fact that light travels as a wave, is almost always hiding in plain sight; a prism simply reveals that it was there. For instance, sunlight is a mixture of many different colors of light, each bobbing up and down with their own characteristic frequency. But taken together the colors merge into a uniform yellowish glow. A prism, or something like it, can also undo this splitting, mixing a rainbow back into a single beam. Back in the late 1970s, scientists figured out how to generate many colors of light, evenly spaced in frequency, and mix them together—a creation that became known as a frequency comb because of the spiky way the frequencies lined up like the teeth on a comb. They also overlapped the crests of the different frequencies in one spot, making the colors come together to form short pulses of light rather than one continuous beam. As frequency comb technology developed, scientists realized that they could enable new laboratory developments, such as ultra-precise optical atomic clocks, and by 2005 frequency combs had earned two scientists a share of the Nobel Prize in physics. These days, frequency combs are finding uses in modern technology, by helping self-driving cars to “see” and allowing optical fibers to transmit many channels worth of information at once, among others. Now, a collaboration of researchers at the University of Maryland (UMD) has proposed a way to make chip-sized frequency combs ten times more efficient by harnessing the power of topology—a field of abstract math that underlies some of the most peculiar behaviors of modern materials. The team, led by JQI Fellows Mohammad Hafezi and Kartik Srinivasan, as well as Yanne Chembo, an associate professor of electrical and computer engineering at UMD and a member of the Institute for Research in Electronics and Applied Physics, published their result recently in the journal Nature Physics.

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