Researchers Mitsuyoshi Kamba, Naoki Hara, and Kiyotaka Aikawa of the University of Tokyo have demonstrated that the motion of a nanoscale particle can be quantum squeezed, meaning its motion can exhibit less uncertainty than the standard quantum mechanical fluctuations. The journal Science reported their findings.
A single nanoparticle confined in a focused laser beam. Image Credit: University of Tokyo
Since improving sensor accuracy is crucial for many modern technologies, this achievement could pave the way for applications such as highly precise autonomous driving, GPS-free navigation, and advancements in fundamental physics research.
The physical universe at the macroscale, from dust particles to planets, is regulated by Newton’s classical mechanics rules developed in the seventeenth century. The principles of quantum mechanics control the physical universe at the microscale, atoms and below, resulting in phenomena that are rarely witnessed at the macroscale. One such phenomenon is “uncertainty” in the quantum realm, which limits measurement precision due to quantum mechanical fluctuations.
For example, zero-point fluctuation refers to the quantum mechanical uncertainty in a confined particle’s position and velocity, even when the particle is in its lowest possible energy state. Quantum squeezing is the creation of a quantum mechanical state with lower uncertainty than the zero-point fluctuation.
Precisely measuring something at the quantum mechanical limit is essential not only for deepening our understanding of the natural world but also for advancing next-generation technologies that could be influenced by quantum effects.
Although quantum mechanics has been successful with microscopic particles, such as photons and atoms, it has not been explored to what extent quantum mechanics is correct at macroscopic scales. One reason for this is that it has been challenging to prepare an appropriate experimental condition to explore quantum mechanics for large, that is, nanoscale, objects.
Kiyotaka Aikawa, Principal Investigator, University of Tokyo
The researchers aimed to identify a particle that could serve as a platform for exploring quantum phenomena at the nanoscale. To reduce uncertainty, they used a nanoscale glass particle, levitated in a vacuum and cooled to its lowest possible energy state.
After ensuring that the particle's trapping potential was appropriately regulated, the researchers released it and allowed it to fly for a brief period of time, measuring its velocity immediately before release. Repeating this method yielded the particle's velocity distribution in this potential.
“When the time before the release is optimal, the velocity distribution is narrower than the velocity uncertainty of the lowest energy level, which is a signature of quantum squeezing,” explained Aikawa.
After years of work, the researchers were eventually able to show quantum squeezing, since the numerous technical challenges they encountered caused fluctuations in the particle. The levitation itself caused significant complications. However, these hurdles did not deter them, and they do not intend to stop now.
“When we found a condition that could be reliably reproduced, we were surprised how sensitive the levitated nanoscale particle was to the fluctuations of its environment. This levitated small particle isolated in a vacuum environment will be an ideal system to explore the transition between quantum mechanics and classical mechanics and to develop new kinds of quantum devices in the future,” concluded Aikawa.
Journal Reference:
Kamba, M., et al. (2025) Quantum squeezing of a levitated nanomechanical oscillator. Science. doi.org/10.1126/science.ady4652