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SBU’s Qiang Li Collaborated on Discovery That Can Advance Quantum Computing

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Qiang Li, SUNY Empire Innovation Professor in the Department of Physics and Astronomy and Stony Brook University, is co-author of a paper with Jigang Wang, a senior scientist at the U.S. Department of Energy’s Ames Laboratory and a professor of physics and astronomy at Iowa State University, that is published in Nature Materials about the discovery of a new light-induced switch that twists the crystal lattice of a Weyl semimetal, switching on a giant electron current that appears to be nearly dissipationless. The discovery and control of such properties brings these materials another step closer to use in applications such as quantum computing. 

Schematics of light-induced coherent phonons that break crystal inversion symmetry and lead to the formation of Weyl points in a Dirac semimetal ZrTe5
Schematics of light-induced coherent phonons that break crystal inversion symmetry and lead to the formation of Weyl points in a Dirac semimetal ZrTe5

Li, who also holds a joint appointment at Brookhaven National Laboratory as leader of the Advanced Energy Materials Group, collaborated on the project with scientists at the U.S. Department of Energy’s Ames Laboratory, Brookhaven Laboratory and the University of Alabama at Birmingham. Pedro Lozano, Li’s PhD student, is also involved in the research.

Weyl and Dirac semimetals can host exotic, nearly dissipationless, electron conduction properties that take advantage of the unique state in the crystal lattice and electronic structure of the material that protects the electrons from doing so. These anomalous electron transport channels, protected by symmetry and topology, don’t normally occur in conventional metals such as copper. After decades of being described only in the context of theoretical physics, there is growing interest in fabricating, exploring, refining and controlling their topologically protected electronic properties for device applications. For example, wide-scale adoption of quantum computing requires building devices in which fragile quantum states are protected from impurities and noisy environments. One approach to achieve this is through the development of topological quantum computation, in which qubits (quantum bits) are based on “symmetry-protected” dissipationless electric currents that are immune to noise.

“What we’ve lacked until now is a low energy and fast switch to induce and control symmetry of these materials,” said Li. “Our discovery of a light symmetry switch opens a fascinating opportunity to carry dissipationless electron current, a topologically protected state that doesn’t weaken or slow down when it bumps into imperfections and impurities in the material.”

“Light-induced lattice twisting, or a phononic switch, can control the crystal inversion symmetry and photogenerate giant electric current with very small resistance,” said Wang. “This new control principle does not require static electric or magnetic fields and has much faster speeds and lower energy cost.”

In this experiment, the team altered the symmetry of the electronic structure of the material using laser pulses to twist the lattice arrangement of the crystal. This light switch enables “Weyl points” in the material, causing electrons to behave as massless particles that can carry the protected, low dissipation current that is sought after.

Qiang Li’s research was supported by the U.S. Department of Energy, Office of Basic Energy Science.

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