Measurement of gravity using feedback-cooled mechanical oscillators

2023 Fiscal Year Final Research Report

• Project/Area Number: 19H00671
• Research Category: Grant-in-Aid for Scientific Research (A)
• Allocation Type: Single-year Grants
• Section: 一般
• Review Section: Medium-sized Section 15:Particle-, nuclear-, astro-physics, and related fields
• Research Institution: Gakushuin University (2021-2023); Tohoku University (2019-2020)
• Principal Investigator: Matsumoto Nobuyuki 学習院大学, 理学部, 准教授 (30750294)
• Project Period (FY): 2019-04-01 – 2024-03-31
• Keywords: 光計測 / 光共振器 / 低散逸振動子 / 重力定数 / 量子制御 / 光ばね / フィードバック冷却

Outline of Final Research Achievements

Aiming to measure microgravi using mechanical oscillators under feedback cooling, the following four objectives were achieved: (1) development of a suspended mirror by two wires, with a Q value greater than 1 million, (2) development of an optical cavity with five times shorter length, (3) development of a stabilized light source capable of 3 × 10^-18 m/sqrt(Hz) @ 500 Hz, and (4) development of vacuum-compatible low-frequency vibration isolation devices (>0.5 Hz). Objective (1) sufficiently reduced thermal noise, and the use of two suspension wires enabled the realization of a compact cavity insensitive to frequency noise as in (2). With (3) and (4), both laser noise and ground vibration were adequately mitigated.

Furthermore, toward achieving quantum control of massive oscillators, the following two objectives were accomplished: (5) development of quantum filters for realizing conditional quantum control, and (6) elucidation of the limits of Q-value enhancement by optical springs.

Free Research Field

量子制御

Academic Significance and Societal Importance of the Research Achievements

冷却振動子を用いることで従来よりも微小なスケールで重力測定を実現すれば、度量衡分野で大きな問題となっている重力定数の系統誤差の低減が期待されるほか、近年、基礎物理学の分野で大きな注目を集めている重力相互作用の量子的性質の解明につながることも期待される。重力は極めて弱いため、これらの目標を実現するためには、種々の雑音を極限まで低減するための地道な技術開発を進めるほかはない。本研究では、熱雑音、光源雑音、地面振動という3つの重要な雑音の低減に成功した。また、重力の量子性解明に向けて、巨視的な物体を量子制御するための新たな手法を開発することに成功した。