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Hajime Okamoto

Bio: Hajime Okamoto is an academic researcher from Nippon Telegraph and Telephone. The author has contributed to research in topics: Resonator & Cantilever. The author has an hindex of 12, co-authored 38 publications receiving 725 citations. Previous affiliations of Hajime Okamoto include Waseda University & École Polytechnique Fédérale de Lausanne.

Papers
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Journal ArticleDOI
TL;DR: In this article, it was shown that phonons can be coherently transferred between two nanomechanical resonators, and the technique of controlling the coupling between nanoscale oscillators using a piezoelectric transducer is useful for manipulating classical oscillations, but if extended to the quantum regime it could also enable entanglement of macroscopic mechanical objects.
Abstract: It is now shown that phonons can be coherently transferred between two nanomechanical resonators, it is now shown. The technique of controlling the coupling between nanoscale oscillators using a piezoelectric transducer is useful for manipulating classical oscillations, but if extended to the quantum regime it could also enable entanglement of macroscopic mechanical objects.

321 citations

Journal ArticleDOI
TL;DR: In this article, a phonon cavity from different oscillating modes of the resonator is used to investigate physics not accessible in their analogous, but better developed, quantum-optics counterpart.
Abstract: Conventional approaches to optomechanics control and monitor the motion of nanoscale mechanical resonators by coupling it to a high-quality photonic cavity. An all-mechanical implementation is now demonstrated by creating a so-called phonon cavity from different oscillating modes of the resonator. This idea opens a route to using solid-state systems to investigate physics not accessible in their analogous, but better developed, quantum-optics counterpart.

134 citations

Journal ArticleDOI
TL;DR: These results suggest that an electromechanical simulator could be built for the Ising Hamiltonian in a nontrivial configuration, namely, for a large number of spins with multiple degrees of coupling.
Abstract: Solving intractable mathematical problems in simulators composed of atoms, ions, photons, or electrons has recently emerged as a subject of intense interest. We extend this concept to phonons that are localized in spectrally pure resonances in an electromechanical system that enables their interactions to be exquisitely fashioned via electrical means. We harness this platform to emulate the Ising Hamiltonian whose spin 1/2 particles are replicated by the phase bistable vibrations from the parametric resonances of multiple modes. The coupling between the mechanical spins is created by generating two-mode squeezed states, which impart correlations between modes that can imitate a random, ferromagnetic state or an antiferromagnetic state on demand. These results suggest that an electromechanical simulator could be built for the Ising Hamiltonian in a nontrivial configuration, namely, for a large number of spins with multiple degrees of coupling.

90 citations

Journal ArticleDOI
TL;DR: Carrier-induced dynamic backaction in micromechanical resonators is demonstrated and optomechanical coupling does not require any optical cavities but is instead based on the piezoelectric effect that is generated by photoinduced carriers.
Abstract: Carrier-induced dynamic backaction in micromechanical resonators is demonstrated. Thermal vibration of an n-GaAs/i-GaAs bilayer cantilever is amplified by optical band-gap excitation, and for the excitation power above a critical value, self-oscillations are induced. These phenomena are found in the [1[over ¯]10]-oriented cantilever, whereas the damping (deamplification) is observed in the [1[over ¯]10] orientation. This optomechanical coupling does not require any optical cavities but is instead based on the piezoelectric effect that is generated by photoinduced carriers.

52 citations

Journal ArticleDOI
TL;DR: In this paper, the eigenfrequency of a doubly clamped GaAs beam shifts downward in proportion to laser power due to optically induced thermal stress, which modifies the spring constant of the resonator.
Abstract: Frequency tuning of two mechanically coupled microresonators by laser irradiation is demonstrated. The eigenfrequency of a doubly clamped GaAs beam shifts downward in proportion to laser power due to optically induced thermal stress, which modifies the spring constant of the resonator. This frequency tuning enables the control of the coupling efficiency and thus the realization of perfect coupling between the micromechanical resonators, i.e., purely symmetric and anti-symmetric coupled vibration. This optical tuning is a valuable method for the study of physics in coupled resonators as well as for expanding the applications of micromechanical resonators for sensors, filters, and logics.

42 citations


Cited by
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Journal ArticleDOI
04 Nov 2016-Science
TL;DR: It is shown that an optical processing approach based on a network of coupled optical pulses in a ring fiber can be used to model and optimize large-scale Ising systems, and a coherent Ising machine outperformed simulated annealing in terms of accuracy and computation time for a 2000-node complete graph.
Abstract: The analysis and optimization of complex systems can be reduced to mathematical problems collectively known as combinatorial optimization. Many such problems can be mapped onto ground-state search problems of the Ising model, and various artificial spin systems are now emerging as promising approaches. However, physical Ising machines have suffered from limited numbers of spin-spin couplings because of implementations based on localized spins, resulting in severe scalability problems. We report a 2000-spin network with all-to-all spin-spin couplings. Using a measurement and feedback scheme, we coupled time-multiplexed degenerate optical parametric oscillators to implement maximum cut problems on arbitrary graph topologies with up to 2000 nodes. Our coherent Ising machine outperformed simulated annealing in terms of accuracy and computation time for a 2000-node complete graph.

555 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss different techniques for sensitive position detection and give an overview of the cooling techniques that are being employed, including sideband cooling and active feedback cooling, and conclude with an outlook of how state-of-the-art mechanical resonators can be improved to study quantum mechanics.

399 citations

Journal ArticleDOI
TL;DR: This work highlights the importance of knowing the carrier and removal status of these materials before, during, and after the construction of the coatings.
Abstract: 2.4. Temperature Effects 527 2.4.1. Effect on Material Properties 528 2.4.2. Effect on Geometry 528 3. Detection Schemes 528 3.1. Optical Lever 528 3.2. Interferometer 529 3.3. Piezoresistive 529 3.4. Capacitive 529 4. Design, Materials, and Fabrication 529 4.1. Design Considerations 530 4.2. Fabrication of Silicon-based Cantilevers 530 4.2.1. Film Deposition 530 4.2.2. Photolithography 530 4.2.3. Etching 530 4.2.4. Doping 530 4.3. Fabrication of Polymeric Cantilevers 531 5. Chemical Selectivity 531 6. Chemical Applications 533 6.1. Volatile Organics 533 6.2. Chemical Warfare Agents 534 6.3. Explosives 534 6.4. Toxic Metal Ions 534 7. Biological Applications 534 7.1. Cells 534 7.2. Viruses 534 7.3. Antigen−Antibody Interactions 535 7.4. DNA Hybridization 536 7.5. Enzymes 537 8. Recommendations for Future Work 538 8.1. Guidelines for Reporting Sensor Performance 538 8.2. Experimental Design Considerations 538 8.3. Fruitful Areas for Further Research 539 8.3.1. More Selective Coatings 539 8.3.2. Increased Sensitivity and Faster Response 539

349 citations

Journal ArticleDOI
TL;DR: In this article, it was shown that phonons can be coherently transferred between two nanomechanical resonators, and the technique of controlling the coupling between nanoscale oscillators using a piezoelectric transducer is useful for manipulating classical oscillations, but if extended to the quantum regime it could also enable entanglement of macroscopic mechanical objects.
Abstract: It is now shown that phonons can be coherently transferred between two nanomechanical resonators, it is now shown. The technique of controlling the coupling between nanoscale oscillators using a piezoelectric transducer is useful for manipulating classical oscillations, but if extended to the quantum regime it could also enable entanglement of macroscopic mechanical objects.

321 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss different techniques for sensitive position detection and give an overview of the cooling techniques that are being employed, including sideband cooling and active feedback cooling, and conclude with an outlook of how state-of-the-art mechanical resonators can be improved to study quantum physics.
Abstract: Mechanical systems are ideal candidates for studying quantumbehavior of macroscopic objects. To this end, a mechanical resonator has to be cooled to its ground state and its position has to be measured with great accuracy. Currently, various routes to reach these goals are being explored. In this review, we discuss different techniques for sensitive position detection and we give an overview of the cooling techniques that are being employed. The latter include sideband cooling and active feedback cooling. The basic concepts that are important when measuring on mechanical systems with high accuracy and/or at very low temperatures, such as thermal and quantum noise, linear response theory, and backaction, are explained. From this, the quantum limit on linear position detection is obtained and the sensitivities that have been achieved in recent opto and nanoelectromechanical experiments are compared to this limit. The mechanical resonators that are used in the experiments range from meter-sized gravitational wave detectors to nanomechanical systems that can only be read out using mesoscopic devices such as single-electron transistors or superconducting quantum interference devices. A special class of nanomechanical systems are bottom-up fabricated carbon-based devices, which have very high frequencies and yet a large zero-point motion, making them ideal for reaching the quantum regime. The mechanics of some of the different mechanical systems at the nanoscale is studied. We conclude this review with an outlook of how state-of-the-art mechanical resonators can be improved to study quantum {\it mechanics}.

316 citations