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Microwave amplification with nanomechanical resonators


The sensitive measurement of electrical signals is at the heart of modern technology. According to the principles of quantum mechanics, any detector or amplifier necessarily adds a certain amount of noise to the signal, equal to at least the noise added by quantum fluctuations1,2. This quantum limit of added noise has nearly been reached in superconducting devices that take advantage of nonlinearities in Josephson junctions3,4. Here we introduce the concept of the amplification of microwave signals using mechanical oscillation, which seems likely to enable quantum-limited operation. We drive a nanomechanical resonator with a radiation pressure force5,6,7, and provide an experimental demonstration and an analytical description of how a signal input to a microwave cavity induces coherent stimulated emission and, consequently, signal amplification. This generic scheme, which is based on two linear oscillators, has the advantage of being conceptually and practically simpler than the Josephson junction devices. In our device, we achieve signal amplification of 25 decibels with the addition of 20 quanta of noise, which is consistent with the expected amount of added noise. The generality of the model allows for realization in other physical systems as well, and we anticipate that near-quantum-limited mechanical microwave amplification will soon be feasible in various applications involving integrated electrical circuits.

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Figure 1: Electromechanical microwave amplification.
Figure 2: Amplification mechanism.
Figure 3: Amplifier gain.

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We would like to thank S. Paraoanu and H. Seppä for discussions. This work was supported by the Academy of Finland and by the European Research Council (grant numbers 240362-Heattronics and 240387-NEMSQED) and EU-FP7-NMP-246026.

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Authors and Affiliations



F.M. and T.T.H. developed the theory. J.-M.P. and S.U.C. contributed to the design and fabrication of the samples and to the cryogenic set-up. H.S. made the samples. P.J.H. and M.A.S. designed the experimental set-up. M.A.S. initiated the work and carried out the measurements.

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Correspondence to F. Massel.

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The authors declare no competing financial interests.

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The file contains Supplementary Text and Data 1-2, Supplementary Figures 1-6 with legends and additional references. (PDF 1555 kb)

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Massel, F., Heikkilä, T., Pirkkalainen, JM. et al. Microwave amplification with nanomechanical resonators. Nature 480, 351–354 (2011).

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