UW–Madison named member of new $25 million Midwest quantum science institute

cartoon showing a quantum hardware network

As joint members of a Midwest quantum science collaboration, the University of Wisconsin–Madison, the University of Illinois at Urbana–Champaign and the University of Chicago have been named partners in a National Science Foundation Quantum Leap Challenge Institute, NSF announced Tuesday.

The five-year, $25 million NSF Quantum Leap Challenge Institute for Hybrid Quantum Architectures and Networks (HQAN) was one of three in this first round of NSF Quantum Leap funding and helps establish the region as a major hub of quantum science. HQAN’s principal investigator, Brian DeMarco, is a professor of physics at UIUC. UW–Madison professor of physics Mark Saffman and University of Chicago engineering professor Hannes Bernien are co-principal investigators.

“HQAN is very much a regional institute that will allow us to accelerate in directions in which we’ve already been headed and to start new collaborative projects between departments at UW–Madison as well as between us, the University of Illinois, and the University of Chicago.” says Saffman, who is also director of the Wisconsin Quantum Institute. “These flagship institutes are being established as part of the National Quantum Initiative Act that was funded by Congress, and it is a recognition of the strength of quantum information research at UW–Madison that we are among the first.”

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cartoon showing a quantum hardware network
In a hybrid quantum network, hardware for storing and processing quantum information is linked together. This design could be beneficial for applications that rely on distributed quantum computing resources. | Credit: E. Edwards, IQUIST

New method measures temperature within 3D objects

four infrared images of the fused silica window used

University of Wisconsin–Madison engineers have made it possible to remotely determine the temperature beneath the surface of certain materials using a new technique they call depth thermography. The method may be useful in applications where traditional temperature probes won’t work, like monitoring semiconductor performance or next-generation nuclear reactors.

Many temperature sensors measure thermal radiation, most of which is in the infrared spectrum, coming off the surface of an object. The hotter the object, the more radiation it emits, which is the basis for gadgets like thermal imaging cameras.

Depth thermography, however, goes beyond the surface and works with a certain class of materials that are partially transparent to infrared radiation.

“We can measure the spectrum of thermal radiation emitted from the object and use a sophisticated algorithm to infer the temperature not just on the surface, but also underneath the surface, tens to hundreds of microns in,” says Mikhail Kats, a UW–Madison professor of electrical and computer engineering. “We’re able to do that precisely and accurately, at least in some instances.”

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four infrared images of the fused silica window used
An infrared image of the fused silica window used to test the depth thermography concept. For the project, the team heated the silica, a type of glass, and analyzed it using a spectrometer. They then measured temperature readings from various depths of the sample. IMAGE COURTESY OF MIKHAIL KATS

Chicago Quantum Summit to gather international experts

abstract graphic of atoms

Top experts in quantum technology from around the globe — including experts from the Wisconsin Quantum Institute — will gather at the University of Chicago on Oct. 25 to discuss the future of quantum information science and strategies to build a quantum workforce.

The second annual Chicago Quantum Summit, hosted by the Chicago Quantum Exchange, will engage scientific and government leaders and the industries that will drive the applications of emerging quantum information science.

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WQI scientists earn grant to improve materials for quantum sensing, computing

four panels of images showing quantum sensors and qubits used in the lab and to develop quantum computers

Researchers at the Wisconsin Quantum Institute (WQI) have been awarded a US Department of Energy grant to study the noise that hampers advances in quantum systems, including quantum computers.

The three-year, $4 million funding will allow the researchers to apply emerging tools to identify new materials and fabrication methods that can improve the performance of these systems.

“All of physics is quantum on some level, and quantum systems let you understand how physics works when you get to the cleanest, smallest, most isolated systems,” says Shimon Kolkowitz, assistant professor of physics at the University of Wisconsin–Madison and lead investigator of the grant. “We think that quantum computing, and quantum technologies more generally, are a really promising area of technological development and research.”

Quantum systems — which make use of single atoms or electrons and the quantum mechanical properties that govern them — have the potential to push boundaries in such areas as computing, precision sensing, and secure communications.

Quantum computers, for example, allow scientists to simulate quantum mechanics in ways that classical computers cannot. But, the computing power of quantum computers has not yet exceeded classical ones.

a grayscale image of a scanning electron micrograph of one of the double quantum dot qubits
A scanning electron microscope image of a gate-defined double quantum dot qubit fabricated by the Eriksson group.

A limiting factor in quantum computing power is the number of qubits, or quantum bits, that can be strung together. Like bits in a classic computer, the more qubits in a quantum computer, the more the computing power. And the limiting factor in how many qubits can be connected with each other while remaining in the fragile quantum states required to perform a computation — called “coherence”  in quantum lingo — is their resistance to external environmental factors, or “noise” that may cause them to “decohere.”

However, researchers have found that the materials used to make the qubits themselves generate a lot of this noise.

“People for quite a while have seen this noise, treated it as a fact of nature, and tried to design around it. But no one really knows what it is or how to get rid of it,” Kolkowitz says. “Even more fundamentally than just understanding or reducing this noise, we think that if you can reduce or ultimately eliminate this noise, it actually opens up the design space for the kinds of qubits you can build, and that will make it much easier to wire qubits together.”

With the DOE funding, Kolkowitz, along with colleagues at WQI and the Livermore National Laboratory, seeks to first identify the nature of the noise and how specific materials contribute to it, and then to develop ways to reduce it.

small white dots, representing single atom defects, are visible in a dark purplish background that is from a diamond
Atom-size quantum defects in a diamond, imaged using a confocal microscope in the Kolkowitz lab.

Work in Kolkowitz’s group, as well as that of Victor Brar, assistant professor of physics and co-investigator on the grant, has led to the development of quantum sensors that allow the researchers to characterize things like magnetic fields at the nanometer scale, or to see how single atoms are arranged in various materials. Part of the DOE funding will be used to continue improving these sensors.

Kolkowitz and Brar then want to use their sensors to identify the noise affecting qubits designed by UW quantum computing researchers Mark Eriksson and Robert McDermott.

“And then we can work in a feedback loop, where, for example, Robert McDermott makes samples and characterizes their performance, then we study the noise limiting that performance with these quantum and nanoscale probes to figure out what’s happening on the microscopic scale,” Kolkowitz says. “Then, we give that information to our theory collaborators here and at Livermore who build models and simulations based on what we’ve measured. And then Robert can use what we’ve learned to design and make new samples to see if we’ve improved on these issues.”

scanning tunneling micrograph showing graphene with a single atomic defect as a white dot in the center.
An image taken with a scanning tunneling microscope of a single atomic defect in graphene

Trying to identify sources of this noise is nothing new, but what Kolkowitz finds most promising about the work funded through this grant is the development and application of new sensing technologies.

“These emerging tools that use quantum states and quantum systems themselves should give us access to the origins and behavior of noise in quantum platforms on scales that haven’t been accessible before,” Kolkowitz says.

Other WQI members who are co-investigators on the grant include Jennifer Choy, Laura Faoro, Mark Friesen, and Alex Levchenko.

Not so defective, after all: Demystifying advanced quantum materials

Jason Kawasaki adjusting a piece of metal equipment in his lab

Sometimes, flaws are what makes a thing special.

That’s the case for a type of material called optical quantum emitters, which send out light in an exceptionally precise manner, one photon at a time, often due to tiny imperfections in a crystal’s structure.

The ability to emit light one photon at a time could allow optical quantum emitters to become the backbones of ultrafast computers, super high-resolution sensors and uncrackable long-range secure communication technologies.

Recently, buzz has been building about a newly discovered variety of quantum emitters consisting of two-dimensional materials (think flat sheets only as thick as a single molecule, similar to graphene). But there’s a hitch: No one truly understands the exact natures of the tiny flaws, called defects, that cause these two-di materials to become optical quantum emitters. And that’s been a major obstacle in obtaining these potentially useful materials.

This story continues on the College of Engineering’s site.