Controlling the motion of macroscopic mechanical oscillators with extreme precision in the quantum regime is a central challenge in modern physics. In this context, optically levitated nanoparticles offer a promising platform because they are well isolated from environmental noise and can be released into free space, enabling free expansion of their wave function.
Recent experiments have achieved ground-state cooling of a single translational mode of a levitated nanoparticle. However, achieving ground-state cooling while simultaneously cooling all other modes has remained challenging. Furthermore, little is known about the dynamics of such particles during free flight near the ground state.
This book demonstrates feedback cooling of all external degrees of freedom—three translational and three rotational motions—of a levitated nanoparticle. In particular, one of the translational modes is cooled to its quantum ground state. Moreover, it presents the first direct measurement of a nanoparticle’s velocity distribution in its motional ground state by temporarily releasing the particle from the optical trap.
These achievements mark a significant step toward the observation of macroscopic quantum interference and pave the way for applications to ultra-high precision sensing, including accelerometry and torque detection.
This book is intended for graduate students and researchers in atomic, molecular, and optical physics and quantum optics.
Table of Contents:
Introduction.- Theoretical background of levitated nanoparticles.- Experimental setup.- Cooling translational motion.- Cooling librational motion.- Time of flight measurement of the velocity distribution.- Conclusion and outlook.
About the Author :
Mitsuyoshi Kamba received his B.Sc. in Physics from Meiji University in 2020, his M.Sc. in Physics from Tokyo Institute of Technology in 2022, and his D.Sc. from the Institute of Science Tokyo in 2025. His research focuses on levitated optomechanics, quantum ground-state cooling, and macroscopic quantum phenomena. His doctoral work demonstrated feedback cooling of all external degrees of freedom (both translational and librational) of a nanoparticle levitated in a one-dimensional optical lattice as well as the direct measurement of the particle’s velocity distribution in its motional ground state. His research has been published in renowned peer-reviewed journals such as Physical Review A, Optics Express, Nature Communications, and Physical Review Letters. He was awarded the JSPS Research Fellowship for Young Scientists (DC2) and the Tokyo Tech Advanced Human Resource Development Fellowship supported by the Japan Science and Technology Agency (JST). He is currently a postdoctoral researcher at the Department of Physics, The University of Tokyo.
