2025-09-19 東京大学
図1：速度揺らぎの時間的な変化
縦軸はナノ粒子の速度の分散を基底状態の速度の分散で規格化した値、横軸は時間。ナノ粒子を捕捉するレーザー光の強度を変えることで、速度揺らぎ（赤い点で表示；実線は理論的な式によるフィッティングを示す）が時間的に変化する状態を生成する。グレーで覆われた領域は量子基底状態より揺らぎの小さい状態であり、この領域への到達が量子スクイージングの実現を示す。量子基底状態の温度は、絶対零度（-273.15 °C）に限りなく近い約6マイクロケルビン（μK）である。
＜関連情報＞
浮遊ナノ機械振動子の量子スクイージング Quantum squeezing of a levitated nanomechanical oscillator
Mitsuyoshi Kamba, Naoki Hara, and Kiyotaka Aikawa
Science Published:18 Sep 2025
DOI:https://doi.org/10.1126/science.ady4652
Editor’s summary
Recent work has demonstrated the ability to cool macroscopic mechanical systems to their quantum mechanical ground state. Kamba et al. now take this a step further to demonstrate the quantum mechanical effect of squeezing in the motional state of a levitated silica microsphere, squeezing results from the knowledge of one parameter to be sacrificed to gain better precision of its conjugate parameter. In this case, knowledge of position was relaxed, resulting in a sharpening of the velocity distribution function. These results should allow quantum mechanical effects to be explored further in macroscopic systems and may find applications in advanced quantum sensing technologies. —Ian S. Osborne
Abstract
Manipulating the motion of macroscopic objects near their quantum mechanical uncertainties has been desired in diverse fields, including fundamental physics, sensing, and transducers. Despite progress in ground-state cooling of a levitated solid particle, realizing its nonclassical states has been elusive. Here, we demonstrate quantum squeezing of the motion of a single nanoparticle by rapidly varying its oscillation frequency. We reveal appreciable narrowing of the velocity variance to –4.9 ± 0.1 decibels of that of the ground state using free-expansion measurements. Our work shows that a levitated nanoparticle offers an ideal platform for studying nonclassical states of its motion and provides a route to developing applications in quantum sensing and exploring quantum mechanics at a macroscopic scale.
