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研究者情報 |
研究者業績
基本情報
研究分野
2経歴
4-
2021年4月 - 現在
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2015年4月 - 現在
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2015年12月 - 2019年3月
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2014年4月 - 2015年3月
学歴
3-
2011年4月 - 2014年3月
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2009年4月 - 2011年3月
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2005年4月 - 2009年3月
受賞
2論文
19-
Physical Review Letters, 124, 221102 (2020) 124(22) 2020年6月 査読有り最終著者責任著者
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PHYSICAL REVIEW A 101(1) 2020年1月 査読有りPrecise measurements of the displacement of, and force acting on, a mechanical oscillator can be performed by coupling the oscillator to an optical cavity. Brownian thermal forces represent a fundamental limit to measurement sensitivity which impedes the ability to use precise force measurements as a tool of fundamental enquiry, particularly in the context of macroscopic quantum measurements and tabletop gravitational experiments. A torsion pendulum with a low mechanical resonant frequency can be limited by very small thermal forces-from its suspensions-at frequencies above resonance. Here, we report torque sensing of a 10-mg torsion pendulum formed by a bar mirror, using two optical cavities on either edge. The rotational mode was measured by subtracting the two signals from the cavities, while intracavity radiation pressure forces were used to trap the torsional mode with a 1 kHz optical spring. The resulting torque sensitivity of 20 aN m/root Hz is a record for a milligram-scale torsional oscillator. This allows us to test spontaneous wave-function collapse in a parameter regime that falls in between that tested by space-based experiments, and high-frequency cryogenic cantilevers.
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Physical Review Letters 122(071101) 2019年2月 査読有り
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International Journal of Modern Physics D (ja) 2018年 査読有り
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Progress of Theoretical and Experimental Physics 2018(1) 2018年1月1日 査読有り
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OPTICS EXPRESS 25(12) 13799-13806 2017年6月 査読有りWe propose a new method to optically levitate a macroscopic mirror with two vertical Fabiy-Perot cavities linearly aligned. This configuration gives the simplest possible optical levitation in which the number of laser beams used is the minimum of two. We demonstrate that reaching the standard quantum limit (SQL) of a displacement measurement with our system is feasible with current. technology. The cavity geometry and the levitated mirror parameters are designed to ensure that the Brownian vibration of the mirror surface is smaller than the SQL. Our scheme provides a promising tool for testing macroscopic quantum mechanics. (C) 2017 Optical Society of America
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PHYSICAL REVIEW A 94(3) 033822-1-033822-5 2016年9月 査読有りThermal decoherence is a major obstacle to the realization of quantum coherence for massive mechanical oscillators. Although optical trapping has been used to reduce the thermal decoherence rate for such oscillators, it also increases the rate by subjecting the oscillator to stochastic forces resulting from the frequency fluctuations of the optical field, thereby setting a fundamental limit on the reduction. This is analogous to the noise penalty in an active feedback system. Here, we directly measure the rethermalization process for an initially cooled and optically trapped suspended mirror, and identify the current limiting decoherence rate as due to the optical trap. Our experimental study of the trap-induced decoherence rate will enable future advances in the probing of fundamental quantum mechanics in the bad-cavity regime, such as testing of deformed commutators.
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日本物理学会講演概要集 71 402-402 2016年<p>熱雑音を極限まで低減した機械光学系は巨視的量子力学の検証に用いることができ、注目を浴びている。鏡を機械的に支持すると、支持に伴うロスから熱雑音が導入されてしまうため、我々は光輻射圧のみを用いて鏡を支持する光学浮上の新手法を提案した。この光学浮上方法の安定性検証と浮上手順の確認のため、我々はねじれ振り子を使った基礎実験を行っている。本講演ではねじれ振り子実験の現状について報告する。</p>
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LIVING REVIEWS IN RELATIVITY 19(1) 2016年 査読有りWe present a possible observing scenario for the Advanced LIGO and Advanced Virgo gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We determine the expected sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron-star systems, which are considered the most promising for multi-messenger astronomy. The ability to localize the sources of the detected signals depends on the geographical distribution of the detectors and their relative sensitivity, and 90% credible regions can be as large as thousands of square degrees when only two sensitive detectors are operational. Determining the sky position of a significant fraction of detected signals to areas of 5 deg(2) to 20 deg(2) will require at least three detectors of sensitivity within a factor of similar to 2 of each other and with a broad frequency bandwidth. Should the third LIGO detector be relocated to India as expected, a significant fraction of gravitational-wave signals will be localized to a few square degrees by gravitational-wave observations alone.
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PHYSICAL REVIEW A 92(3) 033825 2015年9月 査読有りQuantum mechanics predicts superpositions of position states even for macroscopic objects. Recently, the use of a quasifreely suspended mirror combined with a laser was proposed to prepare such states [H. Muuller-Ebhardt et al., Phys. Rev. Lett. 100, 013601 (2008)]. One of the key milestones towards this goal is the preparation of the mechanical oscillator mainly driven by measurement-induced backaction in the quantum regime. Here we describe the observation of backaction acting on a suspended 5-mg mirror in the classical regime. Furthermore, its quantum component is estimated to be larger than the thermal fluctuating force due to internal damping of the suspension, by a factor of 1.4 +/- 0.2 at 325 Hz.
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OPTICS EXPRESS 22(11) 12915-12923 2014年6月 査読有りThe preparation of a mechanical oscillator driven by quantum back-action is a fundamental requirement to reach the standard quantum limit (SQL) for force measurement, in optomechanical systems. However, thermal fluctuating force generally dominates a disturbance on the oscillator. In the macroscopic scale, an optical linear cavity including a suspended mirror has been used for the weak force measurement, such as gravitational-wave detectors. This configuration has the advantages of reducing the dissipation of the pendulum (i.e., suspension thermal noise) due to a gravitational dilution by using a thin wire, and of increasing the circulating laser power. However, the use of the thin wire is weak for an optical torsional anti-spring effect in the cavity, due to the low mechanical restoring force of the wire. Thus, there is the trade-off between the stability of the system and the sensitivity. Here, we describe using a triangular optical cavity to overcome this limitation for reaching the SQL. The triangular cavity can provide a sensitive and stable system, because it can optically trap the mirror's motion of the yaw, through an optical positive torsional spring effect. To show this, we demonstrate a measurement of the torsional spring effect caused by radiation pressure forces. (C) 2014 Optical Society of America
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CPT and Lorentz Symmetry-Proceedings of the Sixth Meeting 2014年1月15日 査読有り
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PHYSICAL REVIEW D 88(11) 111101 2013年12月 査読有りAn optical ring cavity is used to place the first laboratory constraints on parity-odd nonrenormalizable Lorentz violation. Variations in resonant frequencies are limited to parts in 10(15). Absolute sensitivity to Lorentz-violating operators of mass dimension 6 is improved by a factor of a million over existing parity-even microwave-cavity bounds. Sensitivity to dimension-8 violations is improved by 14 orders of magnitude.
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PHYSICAL REVIEW LETTERS 110(20) 200401 2013年5月 査読有りA search for Lorentz violation in electrodynamics was performed by measuring the resonant frequency difference between two counterpropagating directions of an optical ring cavity. Our cavity contains a dielectric element, which makes our cavity sensitive to the violation. The laser frequency is stabilized to the counterclockwise resonance of the cavity, and the transmitted light is reflected back into the cavity for resonant frequency comparison with the clockwise resonance. This double-pass configuration enables a null experiment and gives high common mode rejection of environmental disturbances. We found no evidence for odd-parity anisotropy at the level of delta c/c less than or similar to 10(-14). Within the framework of the standard model extension, our result put more than 5 times better limits on three odd-parity parameters (kappa) over tilde (JK)(0+) and a 12 times better limit on the scalar parameter (kappa) over tilde (tr) compared with the previous best limits.
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CLASSICAL AND QUANTUM GRAVITY 28(9) 094011 2011年5月 査読有りThe objectives of the DECi-hertz Interferometer Gravitational Wave Observatory (DECIGO) are to open a new window of observation for gravitational wave astronomy and to obtain insight into significant areas of science, such as verifying and characterizing inflation, determining the thermal history of the universe, characterizing dark energy, describing the formation mechanism of supermassive black holes in the center of galaxies, testing alternative theories of gravity, seeking black hole dark matter, understanding the physics of neutron stars and searching for planets around double neutron stars. DECIGO consists of four clusters of spacecraft in heliocentric orbits; each cluster employs three drag-free spacecraft, 1000 km apart from each other, whose relative displacements are measured by three pairs of differential Fabry-Perot Michelson interferometers. Two milestone missions, DECIGO pathfinder and Pre-DECIGO, will be launched to demonstrate required technologies and possibly to detect gravitational waves.
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PHYSICAL REVIEW LETTERS 106(16) 161101 2011年4月 査読有りWe present the first upper limit on gravitational wave (GW) backgrounds at an unexplored frequency of 0.2 Hz using a torsion-bar antenna (TOBA). A TOBA was proposed to search for low-frequency GWs. We have developed a small-scaled TOBA and successfully found Omega(gw)(f) < 4.3 x 10(17) at 0.2 Hz as demonstration of the TOBA's capabilities, where Omega(gw)(f) is the GW energy density per logarithmic frequency interval in units of the closure density. Our result is the first nonintegrated limit to bridge the gap between the LIGO band (around 100 Hz) and the Cassini band (10(-6)-10(-4) Hz).
MISC
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2023年3月8日We investigated the quantum state of an optomechanical suspended mirror under continuous measurement and feedback control using Wiener filtering. We focus on the impact of the two-mode theory of suspended mirror on the quantum state, which is described by the pendulum and rotational modes. It is derived from the beam model coupled to the cavity light in the low-frequency regime, including the internal friction of the beam and the finite size effect of the mirror. We constructed a Wiener filter for the two-mode theory and predicted the quantum state by evaluating the conditional covariance matrix using Wiener filter analysis. The results demonstrate that multimode analysis may play an important role in generating the quantum squeezed state. We also point out the possibility that one-mode analysis can be a good approximation by choosing the range of the Fourier space in the Wiener filter analysis.
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2022年12月21日Pendulums have long been used as force sensors due to their ultimately low dissipation (high-quality factor) characteristic. They are widely used in the measurement of the gravitational constant, detection of gravitational waves, and determination of ultralight dark matter. Furthermore, it is expected that the quantum nature of gravity will be demonstrated by performing quantum control for macroscopic pendulums. Recently, we have demonstrated that quantum entanglement between two pendulums can be generated using an optical spring [D. Miki, N. Matsumoto, A. Matsumura, T. Shichijo, Y. Sugiyama, K. Yamamoto, and N. Yamamoto, arXiv:2210.13169 (2022)]; however, we have ignored that an optical spring can reduce the quality factor (Q-factor) by applying normal-mode splitting between the pendulum and rotational modes possessing relatively high dissipation. Herein, we analyze a system composed of a cylinder suspended using a beam (a suspended mirror, i.e., a pendulum) and an optical spring to consider normal-mode splitting. The reduction in Q-factor is determined only by the beam parameters: the ratio of the radius of the mirror to the length of the beam, and the ratio of the frequency of the rotational mode to the pendulum mode in the absence of cavity photons. In our analysis, we find that the reduction factor $4.38$ is reproduced, which is consistent with the experimental result in Matsumoto \textit{et al.} [N. Matsumoto, S. B. Catan$\tilde{\text{o } }$-Lopez, M. Sugawara, S. Suzuki, N. Abe, K. Komori, Y. Michimura, Y. Aso, and K. Edamatsu, Phys. Rev. Lett. 122, 071101 (2019)]. Our analysis shows that low dissipation (high quality) can be reached using an optical spring for the realistic pendulum system considering the rotational degree of freedom.
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2022年10月24日This study is aimed at investigating the feasibility of generating quantum entanglement between macroscopic mechanical mirrors in optomechanical systems while under continuous measurement and feedback control. We carefully derive a covariance matrix for mechanical mirrors in a steady state, employing the Kalman filtering problem with an assumed dominant cavity photon dissipation, such that the common and differential modes of the mirrors are squeezed by the action of measuring the output light beams. We demonstrate that entanglement between the mechanical mirrors is generated when the states of the common and differential modes are squeezed with high purity in an asymmetric manner. Our results also show that quantum entanglement between $7$ mg mirrors is achievable in the short term.
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2020年8月25日In quantum mechanics, measurement can be used to prepare a quantum state. This principle is applicable even for macroscopic objects, which may enable us to see classical-quantum transition. Here, we demonstrate conditional mechanical squeezing of a mg-scale suspended mirror (i.e. the center-of-mass mode of a pendulum) near quantum regimes, through continuous linear position measurement and quantum state prediction. The experiment involved the pendulum interacting with photon coherent fields in a detuned optical cavity, which creates an optical spring. Futhermore, the detuned cavity allows us to perform linear position measurement by direct photo-detection of the reflected light. We experimentally verify the conditional squeezing using the theory combining prediction and retrodiction based on the causal and anti-causal filters. As a result, the standard deviation of position and momentum are respectively given by 36 times the zero-point amplitude of position $q_{\rm zpf}$ and 89 times the zero-point amplitude of momentum $p_{\rm zpf}$. The squeezing level achieved is about 5 times closer to the zero-point motion, despite that the mass of the mechanical oscillator is approximately 7 orders of magnitude greater, compared to the previous study. Thus, our demonstration is the first step towards quantum control for massive objects whose mass-scale is high enough to measure gravitational interactions. Such quantum control will pave the way to test quantum mechanics using the center-of-mass mode of massive objects.
書籍等出版物
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Springer Japan 2016年 (ISBN: 9784431558828)https://www.springer.com/gp/book/9784431558804
講演・口頭発表等
11-
WHERE QUANTUM INFORMATION & QUANTUM TECHNOLOGIES MEET GRAVITY IN LABORATORY 2021年3月16日 招待有り
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Quantum sensors of magnetic and inertial forces 2021年3月3日 招待有り
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International Conference on Quantum Metrology and Sensing 2019年12月13日 招待有り
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Quantum Optomechanical Architectures for Dark Matter Detection 2019年10月28日 招待有り
共同研究・競争的資金等の研究課題
10-
JST 創発的研究支援事業 2021年4月 - 2028年3月
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日本学術振興会 科学研究費助成事業 2024年4月 - 2027年3月
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日本学術振興会 卓越研究員 2021年1月 - 2024年3月
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科学研究費助成事業 基盤A 2019年4月 - 2023年3月
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三菱財団 三菱財団自然科学研究助成（一般助成） 2020年10月 - 2021年9月