Scientists from The University of Manchester, in a collaboration led by ETH Zurich and including TU Wien and ICFO Barcelona, have achieved a major breakthrough by cooling the spinning motion of a nanoparticle to its quantum ground state, the coldest possible state of motion.
The study, published in Nature Physics, and carried out at ETH Zurich, demonstrates how researchers used a finely tuned laser and vacuum system to trap and cool a 100-nanometre glass disc composed of billions of atoms. The work sets a new benchmark for quantum purity, a measure of how closely a system behaves according to the rules of quantum mechanics.
Dr. Jayadev Vijayan, a Research Fellow in the Department of Electrical and Electronic Engineering at The University of Manchester, explains: "This high-purity quantum state of motion gives us the best starting point to test whether objects 10,000 times heavier than the current record-holder show wave-like behaviour characteristic of the quantum world."
A new cold source for quantum experiments
In the quantum world, atoms can behave like both particles and waves at the same time, appearing to being "in two places at once" - an effect that only happens in the quantum world.
To observe these effects in larger objects, their motion must be cooled close to absolute zero - where the only remaining motion is due to quantum fluctuations, the jittering of empty space itself.
To achieve this for the first time, researchers used a laser beam to trap a nanoparticle and make it levitate inside a vacuum chamber. The vacuum chamber removes all the air, so nothing can bump into the particle and heat it up. Next, they placed the particle between two mirrors facing each other, forming a cavity to cool the motion of the particle.
Professor Carlos Gonzalez-Ballestero, Institute of Theoretical Physics at TU Wien, explains: "The laser can either supply energy to the nanoparticle or take energy away from it. By carefully adjusting the cavity mirrors, we can make sure that the laser almost always takes energy away. The particle then spins slower and slower until it reaches the quantum ground state."
What makes this result remarkable is the record-breaking purity of the quantum state. High purity means the object is behaving in a way that is almost entirely quantum, with very little influence from the environment. That level of control and precision opens doors to experimental tests of quantum mechanics at completely new scales.
Putting large quantum systems to use
This breakthrough creates a pathway to revolutionary new technologies. The larger a quantum object is, the more sensitive it becomes to certain types of forces, potentially making them incredibly sensitive quantum sensors. For example, levitated nanoparticle-based sensors could provide: a new type of precise navigation system that does not need global satellite systems; early detection systems for earthquakes and volcanic activity; and mapping tools for subterranean topology.
- This research was published in the journal Nature Physics. Full title: High-Purity Quantum Optomechanics at Room Temperature. DOI: 10.1038/s41567-025-02976-9 .Link: https://www.nature.com/articles/s41567-025-02976-9
