Coherent phonon dynamics realized in spatially separated mechanical resonators

The CAS Key Laboratory of Quantum Information makes a significant progress in nanomechanical resonators. A group led by Prof. GUO Guo-Ping, SONG Xiang-Xiang, DENG Guang-Wei (now at UESTC) in collaboration with Prof. TIAN Lin from University of California, Merced, and Origin Quantum Company Limited realized coherent phonon manipulations within spatially separated mechanical resonators. The research results were published online on March, 2nd, in Proceedings of the National Academy of Sciences of the United States of America.

With the rapid development of nanotechnology, devices like surface acoustic wave resonators and nanomechanical resonators are found to be suitable for generation, storage, and manipulation of few or even single phonon, which can be further applied in both classical and quantum information process. The realization of the various applications requires coherent manipulation between different phonon modes. Coherent manipulations within neighbouring phonon modes have been reported previously, while controllable coherent information transfer between spatially separated phonon modes, remains technically challenging. Focusing on this goal, the researchers designed a novel device based on their previous achievements (Nano Lett.16, 5456 (2016)?Nano Lett.17, 915 (2017); Nat. Commun. 9, 383 (2018)). Taking advantages of the extraordinary electronic and mechanical properties of graphene, they realized tunable strong coupling between non-neighbouring phonon modes, mediated by the center phonon mode. By improving sample structure design and measurement technique, the coupling strengths and quality factors are enhanced by one and two orders of magnitude, respectively, comparing to their previous work. The cooperativity reaches 107, which is several orders of magnitude higher than other works. With combined properties of high tunablitiy, large coupling strength, and excellent coherence, the researchers demonstrated electrically tunable Rabi oscillations and Ramsey interferences between non-neighbouring phonon modes in this system.

This work is the first experimental realization of tunable coherent phonon dynamics between non-neighbouring phonon modes. It shows new possibilities towards information storage and processing using phonon modes in nanomechanical resonators, and hybrid devices based on nano-phononics. Reviewers highly evaluated this work: “These results clearly go beyond what has been achieved thus far on the coherent manipulation of resonators in the classical regime.” Taking advantages of the cooling technologies, this work also shed lights on coherent manipulations of phonons in the quantum regime and development of phonon-based novel quantum devices.

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Dr. ZHANG Zhuo-Zhi, Dr. SONG Xiang-Xiang, and Dr. LUO Gang are equally-contributed first authors. This work in China is supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, China Postdoctoral Science Foundation, and Anhui Initiative in Quantum Information Technologies. Part of the sample fabrication is performed at the USTC center for Micro and Nanoscale Research and Fabrication.