System Bits: Aug. 5

Algorithm could advance quantum computing
Scientists at the Los Alamos National Laboratory report the development of a quantum computing algorithm that promises to provide a better understanding of the quantum-to-classical transition, enabling model systems for biological proteins and other advanced applications.

“The quantum-to-classical transition occurs when you add more and more particles to a quantum system,” said Patrick Coles of the Physics of Condensed Matter and Complex Systems group at Los Alamos National Laboratory, “such that the weird quantum effects go away and the system starts to behave more classically. For these systems, it’s essentially impossible to use a classical computer to study the quantum-to-classical transition. We could study this with our algorithm and a quantum computer consisting of several hundred qubits, which we anticipate will be available in the next few years based on the current progress in the field.”

Answering questions about the quantum-to-classical transition is notoriously difficult. For systems of more than a few atoms, the problem rapidly becomes intractable. The number of equations grows exponentially with each added atom. Proteins, for example, consist of long strings of molecules that may become important biological components or sources of disease, depending on how they fold up. Although proteins can be comparatively large molecules, they are small enough that the quantum-to-classical transition, and algorithms that can handle it, become important when trying to understand and predict how proteins fold.

White crosses represent solutions to a simple quantum problem analyzed with a new quantum computer algorithm developed at the Los Alamos National Laboratory. Image provided courtesy of Los Alamos National Laboratory.

In order to study aspects of the quantum-to-classical transition on a quantum computer, researchers first need a means to characterize how close a quantum system is to behaving classically. Quantum objects have characteristics of both particles and waves. In some cases, they interact like tiny billiard balls, in others they interfere with each other in much the same way that waves on the ocean combine to make larger waves or cancel each other out. The wave-like interference is a quantum effect. Fortunately, a quantum system can be described using intuitive classical probabilities rather than the more challenging methods of quantum mechanics, when there is no interference.

The LANL group’s algorithm determines how close a quantum system is to behaving classically. The result is a tool they can use to search for classicality in quantum systems and understand how quantum systems, in the end, seem classical to us in our everyday life.

Soft wearable devices
Researchers at the University of Houston and the Georgia Institute of Technology are separately working on wearable technology, trying to make such devices less obtrusive in everyday life. Both teams are addressing physical and technical challenges in health care.

Wearable human-machine interfaces – devices that can collect and store important health information about the wearer, among other uses – have benefited from advances in electronics, materials, and mechanical designs. But current models still can be bulky and uncomfortable, and they can’t always handle multiple functions at one time.

Researchers report the discovery of a multifunctional, ultrathin wearable electronic device that is imperceptible to the wearer.

The device allows the wearer to move naturally and is less noticeable than wearing a Band-Aid, said Cunjiang Yu, Bill D. Cook Associate Professor of Mechanical Engineering at the University of Houston and lead author for the paper, published as the cover story in Science Advances.

“Everything is very thin, just a few microns thick,” said Yu, who also is a principal investigator at the Texas Center for Superconductivity at UH. “You will not be able to feel it.”

It has the potential to work as a prosthetic skin for a robotic hand or other robotic devices, with a robust human-machine interface that allows it to automatically collect information and relay it back to the wearer.

That has applications for health care – “What if when you shook hands with a robotic hand, it was able to instantly deduce physical condition?” Yu asked – as well as for situations such as chemical spills, which are risky for humans but require human decision-making based on physical inspection.

While current devices are gaining in popularity, the researchers said they can be bulky to wear, offer slow response times and suffer a drop in performance over time. More flexible versions are unable to provide multiple functions at once – sensing, switching, stimulation and data storage, for example – and are generally expensive and complicated to manufacture.

The device described in the paper, a metal-oxide-semiconductor on a polymer base, offers manufacturing advantages and can be processed at temperatures lower than 300 degrees C.

“We report an ultrathin, mechanically imperceptible, and stretchable human-machine interface device, which is worn on human skin to capture multiple physical data and also on a robot to offer intelligent feedback, forming a closed-loop HMI,” the researchers wrote. “The multifunctional soft stretchy HMI device is based on a one-step formed, sol-gel-on-polymer-processed indium zinc oxide semiconductor nanomembrane electronics.”

In addition to Yu, the paper’s co-authors include first author Kyoseung Sim, Zhoulyu Rao, Faheem Ershad, Jianming Lei, Anish Thukral and Jie Chen, all of UH; Zhanan Zou and Jianliang Xiao, both of the University of Colorado; and Qing-An Huang of Southeast University in Nanjing, China.

Meanwhile, at Georgia Tech, the research team came up with a wireless, wearable monitor built with stretchable electronics could allow comfortable, long-term health monitoring of adults, babies, and small children without concern for skin injury or allergic reactions caused by conventional adhesive sensors with conductive gels.

The soft and conformable monitor can broadcast electrocardiogram (ECG), heart rate, respiratory rate, and motion activity data as much as 15 meters to a portable recording device, such as a smartphone or tablet computer. The electronics are mounted on a stretchable substrate and connected to gold, skin-like electrodes through printed connectors that can stretch with the medical film in which they are embedded.

“This health monitor has a key advantage for young children who are always moving, since the soft conformal device can accommodate that activity with a gentle integration onto the skin,” said Woon-Hong Yeo, an assistant professor in the George W. Woodruff School of Mechanical Engineering and the Wallace H. Coulter Department of Biomedical Engineering at Georgia Tech. “This is designed to meet the electronic health monitoring needs of people whose sensitive skin may be harmed by conventional monitors.”

Details of the monitor were reported July 24 in the journal Advanced Science. The research was supported by the Imlay Innovation Fund at Children’s Healthcare of Atlanta, NextFlex (the Flexible Hybrid Electronics Manufacturing Institute), and by a seed grant from the Institute for Electronics and Nanotechnology at Georgia Tech. The monitor has been studied on both animal models and humans.

Because the device conforms to the skin, it avoids signal issues that can be created by the motion of the typical metal-gel electrodes across the skin. The device can even obtain accurate signals from a person who is walking, running or climbing stairs.

“When you put a conventional electrode on the chest, movement from sitting up or walking creates motion artifacts that are challenging to separate from the signals you want to measure,” Yeo said. “Because our device is soft and conformal, it moves with the skin and provides information that cannot be seen with the motion artifacts of conventional sensors.”

Continuous evaluation with a wireless health monitor could improve the assessment of children and help clinicians identify trends earlier, potentially facilitating intervention before a condition progresses, said Dr. Kevin Maher, a pediatric cardiologist at Children’s Healthcare of Atlanta.

“The generation of continuous data from the respiratory and cardiovascular systems could allow for the application of advanced diagnostics to detect changes in clinical status, response to therapies and implementation of early intervention,” Maher said. “A device to literally follow every breath a child takes could allow for early recognition and intervention prior to a more severe presentation of a disease.”

Used in the home, a wearable monitor might detect changes that might not otherwise be apparent, he said. In clinical settings, the wireless device could allow children to feel less “tethered” to equipment. “I see this device as a significant change in pediatric health care and am excited to partner with Georgia Tech on the project,” Maher added.

The monitor uses three gold electrodes embedded in the film that also contains the electronic processing equipment. The entire health monitor is just three inches in diameter, and a more advanced version under development will be half that size. The wireless monitor is now powered by a small rechargeable battery, but future versions may replace the battery with an external radio-frequency charging system.

Yeo and his collaborators, including first author and postdoctoral fellow Yun-Soung Kim, are focusing on pediatric applications because of the need for ambulatory monitoring in children. However, they envision that the health monitor could also be used for other patient groups, including older adults who may also have sensitive skin. For adults, there would be additional advantages.

“The monitor could be worn for multiple days, perhaps for as long as two weeks,” Yeo said. “The membrane is waterproof, so an adult could take a shower while wearing it. After use, the electronic components can be recycled.”

Two versions of the monitor have been developed. One is based on medical tape and designed for short-term use in a hospital or other care facility, while the other uses a soft elastomer medical film approved for use in wound care. The latter can remain on the skin longer.

“The devices are completely dry and do not require a gel to pick up signals from the skin,” Yeo explained. “There is nothing between the skin and the ultrathin sensor, so it is comfortable to wear.”

Because the monitor can be worn for long periods of time, it can provide a long-term record of ECG data helpful to understanding potential heart problems. “We use deep learning to monitor the signals while comparing them to data from a larger group of patients,” Yeo said. “If an abnormality is detected, it can be reported wirelessly through a smartphone or other connected device.”

Fabrication of the monitor’s circuitry uses thin-film, mesh-like patterns of copper that can flex with the soft substrate. The chips are the only part not flexible, but they are mounted on the strain-isolated soft substrate instead of a traditional plastic circuit board.

As next steps, Yeo plans to reduce the size of the device and add features to measure other health-related parameters such as temperature, blood oxygen and blood pressure. A major milestone would be a clinical trial to evaluate performance against conventional health monitors.

For Yeo, who specializes in nano-engineering and micro-engineering, the prospect of seeing the device in clinical trials – and ultimately used in children’s hospitals – is a powerful incentive.

“It will be a dream come true for me to see something we have developed be helpful to someone who is suffering,” he said. “We all want to see developments in science and engineering translated into improved patient care.”

In addition to those already mentioned, paper coauthors included Robert Herbert, Shinjae Kwon, and Musa Mahmood from Georgia Tech; Yongkuk Lee from Wichita State University; Nam Kyun Kim and Hee Cheol Cho from Emory University; and Donghyun Kim from Yonsei University Wonju College of Medicine in Korea.