System Bits: Sept. 24

Quantum states
Many companies and academic researchers are working on quantum computing technology, including the University of Buffalo.

New research on two-dimensional tungsten disulfide (WS2) could open the door to advances in quantum computing, UB reports.

In a paper published Sept. 13 in Nature Communications, scientists report that they can manipulate the electronic properties of this super-thin material in ways that could be useful for encoding quantum data.

The study deals with WS2’s energy valleys, which University at Buffalo physicist Hao Zeng, co-lead author of the paper, describes as “the local energy extrema of the electronic structure in a crystalline solid.”

Valleys correspond with specific energies that electrons can have in a material, and the presence of an electron in one valley versus another can be used to encode information. An electron in one valley can represent a 1 in binary code, while an electron in the other can represent a 0.

The ability to control where electrons might be found could yield advances in quantum computing, enabling the creation of qubits, the basic unit of quantum information. Qubits have the mysterious quality of being able to exist not just in a state of 1 or 0, but in a “superposition” related to both states.

The paper in Nature Communications marks a step toward these future technologies, demonstrating a novel method of manipulating valley states in WS2.

Zeng, PhD, professor of physics in the UB College of Arts and Sciences, led the project with Athos Petrou, PhD, UB Distinguished Professor of Physics, and Renat Sabirianov, PhD, chair of physics at the University of Nebraska Omaha. Additional co-authors included UB physics graduate students Tenzin Norden, Chuan Zhao and Peiyao Zhang. The research was funded by the National Science Foundation.

Tractica forecasts worldwide revenue for enterprise quantum computing will reach $9.1 billion per year by 2030, compared with $111.6 million in 2018. North America will lead the market in revenue, followed by Europe, Asia Pacific, Latin America, and Middle East/Africa. “Quantum computers are not destined to replace the processors in personal computers or smartphones anytime soon,” Keith Kirkpatrick, principal analyst at Tractica, said in a statement. “Significantly scaling the processing power, improving error correction abilities, and writing and refining quantum algorithms will be required before enterprises adopt quantum computing en masse.”

A Harvard chip for neuronal networking
Researchers from Harvard University have developed an electronic chip that can perform high-sensitivity intracellular recording from thousands of connected neurons simultaneously. This breakthrough allowed them to map synaptic connectivity at an unprecedented level, identifying hundreds of synaptic connections.

“Our combination of the sensitivity and parallelism can benefit fundamental and applied neurobiology alike, including functional connectome construction and high-throughput electrophysiological screening,” said Hongkun Park, Mark Hyman Jr. Professor of Chemistry and Professor of Physics, and co-senior author of the paper.

“The mapping of the biological synaptic network enabled by this long sought-after parallelization of intracellular recording also can provide a new strategy for machine intelligence to build next-generation artificial neural network and neuromorphic processors,” said Donhee Ham, Gordon McKay Professor of Applied Physics and Electrical Engineering at the John A. Paulson School of Engineering and Applied Sciences (SEAS), and co-senior author of the paper.

The research is described in Nature Biomedical Engineering.

The researchers developed the electronic chip using the same fabrication technology as computer microprocessors. The chip features a dense array of vertically-standing nanometer-scale electrodes on its surface, which are operated by the underlying high-precision integrated circuit. Coated with platinum powder, each nanoelectrode has a rough surface texture, which improves its ability to pass signals.

Neurons are cultured directly on the chip. The integrated circuit sends a current to each coupled neuron through the nanoelectrode to open tiny holes in its membrane, creating an intracellular access. Simultaneously, the same integrated circuit also amplifies the voltage signals from the neuron picked up by the nanoelectrode through the holes.

“In this way we combined the high sensitivity of intracellular recording and the parallelism of the modern electronic chip,” said Jeffrey Abbott, a postdoctoral fellow in the Department of Chemistry and Chemical Biology and SEAS, and the first author of the paper.

In experiments, the array intracellularly recorded more than 1,700 rat neurons. Just 20 minutes of recording gave researchers a never-before-seen look at the neuronal network and allowed them to map more than 300 synaptic connections.

This work was also co-authored by Tianyang Ye, Keith Krenek, Rona S. Gertner, Steven Ban, Youbin Kim, Ling Qin and Wenxuan Wu. “We also used this high-throughput, high-precision chip to measure the effects of drugs on synaptic connections across the rat neuronal network, and now we are developing a wafer-scale system for high-throughput drug screening for neurological disorders such as schizophrenia, Parkinson’s disease, autism, Alzheimer’s disease, and addiction,” said Abbott.

The research was supported by Samsung Advanced Institute of Technology of Samsung Electronics, the Catalyst Foundation, the U.S. Army Research Office, the National Science Foundation, the National Institutes of Health, and the Gordon and Betty Moore Foundation.