Researchers at the University of Tokyo have pulled off a breakthrough that pushes the boundaries of quantum physics into new territory.
The team successfully demonstrated quantum squeezing of the motion of a nanoscale particle, a motion whose uncertainty is smaller than the quantum mechanical fluctuations usually considered the ultimate limit.
The achievement could open doors not only for probing fundamental physics but also for creating ultra-precise sensors.
These sensors may one day enable technologies such as GPS-free navigation and autonomous driving that operate with pinpoint accuracy.
At the heart of the discovery lies one of quantum mechanics’ strangest features — uncertainty. In the microscopic world, the position and velocity of a particle cannot be measured with absolute precision because they are always subject to fluctuations.
Even in the lowest possible energy state, a particle still experiences “zero-point fluctuations.”
Quantum squeezing reduces this uncertainty, creating a state narrower than nature’s usual quantum limit.
By extending this concept to a nanoscale particle, the Tokyo team has created a new platform to explore how quantum laws apply at scales larger than atoms but still far smaller than everyday objects.
A particle trapped between two worlds
Principal investigator Kiyotaka Aikawa explains the challenge: “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.”
The team needed an object large enough to bridge the gap to test this. They turned to a glass particle at the nanoscale, levitating it in a vacuum where it was cooled to near its lowest possible energy level.
By carefully adjusting the conditions of its trap and then releasing it briefly, the researchers could measure its velocity distribution.
The key moment came when they found that, under the right timing, the velocity distribution was narrower than the uncertainty expected at the particle’s ground state. This narrowing was the unmistakable sign of quantum squeezing.
Engineering the leap to quantum devices
The journey was anything but easy. Levitating particles are notoriously unstable, and the environment added further noise and fluctuations. The researchers spent years overcoming these issues before finding a condition that worked consistently.
“When we found a condition that could be reliably reproduced,” says Aikawa, “we were surprised how sensitive the levitated nanoscale particle was to the fluctuations of its environment.”
This delicate balance is precisely what makes the platform so powerful.
A levitated nanoscale particle in vacuum represents an isolated system where researchers can study the transition between classical and quantum mechanics. It also offers a testbed for building new quantum devices.
Beyond pure science, the implications are practical. Ultra-sensitive quantum sensors developed from this principle could revolutionize navigation by providing accuracy independent of satellite signals.
They might also enhance measurements in fields as diverse as medicine, geology, and communications.
For now, the Tokyo team is celebrating its success. But their work marks only the beginning of a larger journey, one where quantum mechanics edges ever closer to the macroscopic world we inhabit.
The findings of the study have been recently published in the journal Science.