# Cornell receives nearly $3.5M in federal push for quantum information research Four Cornell researchers have received grants from the U.S. Department of Energy as part of a$218 million federal push to advance quantum information science.

The awards, part of the DOE’s Basic Energy Science (BES) program, were made in conjunction with the White House Summit on Advancing American Leadership in Quantum Information Science. At the summit, the administration emphasized the importance of laying the foundation for the next generation of computing and information processing as well as an array of other innovative technologies.

“[Quantum information science] represents the next frontier in the Information Age,” U.S. Secretary of Energy Rick Perry said in a press release announcing the grants. “At a time of fierce international competition, these investments will ensure sustained American leadership in a field likely to shape the long-term future of information processing and yield multiple new technologies that benefit our economy and society.”

The project “Coherent Spin-Magnon Coupling for Quantum-to-Quantum Transduction” was awarded $1.5 million, and is led by Greg Fuchs, associate professor of applied and engineering physics. Co-principal investigators include Dan Ralph, professor of physics, as well as collaborators from the University of Iowa and Ohio State University. The research team will be tackling a fundamental problem of solid-state quantum information technologies: It is very difficult to network local quantum processors with each other. Those systems could be networked, however, if the local quantum bits, which operate at microwave frequencies, could transfer their states coherently into individual photons of light. The research team aims to achieve that by coupling diamond nitrogen-vacancy centers – atomic defects inside diamonds – with magnons, a collective excitation of spins within a magnet. The coupling would provide a key link between microwave-frequency quantum processors and quantum optical networks. “We want to know if high-quality magnetic nanostructures, placed in close proximity to nitrogen-vacancy centers, can form the missing quantum link,” said Fuchs. “To do that, all of the parts will have to work well, and the entire thing will have to be cold – only about a tenth of a degree above absolute zero.” If successful, the research team hopes to be the first to send quantum bits of information between two nitrogen-vacancy centers mediated by magnons. The project “Planar Systems for Quantum Information” was awarded$1.95 million, and is led by Jie Shan, professor of applied and engineering physics. Co-principal investigators include Kin Fai Mak, assistant professor of physics, as well as collaborators from Columbia University, the University of Texas at Austin and SLAC National Accelerator Laboratory, operated by Stanford University.

The research team will investigate a family of two-dimensional semiconductors known as transition metal dichalcogenides – compounds such as molybdenum disulfide and tungsten diselenide – as potential candidates for storing and communicating quantum bits of information. The family of semiconductors has the unique ability to store quantum information in ways other systems can’t.

Most quantum systems use electron charge or spin to represent “degrees of freedom” that can store and process information, but there is a third degree of freedom, known as the valley index, in which electrons can occupy different states in their momentum space but with the same energy.

Those valleys are a new way to represent quantum bits of information, potentially more coherently than with other systems, and with the ability to more precisely tune the information, among other novel functions.

Until recently, there have been few approaches to accessing, much less controlling, valley degree of freedom in solids. But transition metal dichalcogenides offer direct access to the valley by means of optical excitation.

“In these materials, each handedness of light couples only to one of the two independent valleys. The valleys and spins are coupled, providing the possibility of stabilizing excitations within the valley. This is a largely unexploited and unstudied quantum degree of freedom in solids,” said Shan.

The Cornell projects were among 27 chosen by the DOE for funding through its fiscal year 2018 BES Quantum Information Science Research Awards program. Twenty-one of the awarded projects are university-based; Cornell was the only university with multiple awardees.

Syl Kacapyr is public relations and content manager for the College of Engineering.

This story also appeared in the Cornell Chronicle.

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