Researchers from the University of Florence, CNR-INO, INFN and LENS have observed steady-state entanglement between the motion of a levitating nanoparticle and light propagating out of an optical cavity — at room temperature.

Entanglement is one of the most distinctive phenomena in quantum mechanics: two systems can share correlations that have no explanation in classical physics and that defy common intuition. Generating this kind of link between light and the motion of a material object has long been one of the goals of physics research, particularly in the field known as quantum optomechanics.

In the experiment, a glass sphere of approximately 100 nanometres in diameter is held suspended in vacuum by an optical tweezer (a tightly focused laser beam), and placed inside a resonator (optical cavity) formed by a pair of mirrors. Two separate lasers play complementary roles: one cools and stabilises the particle’s motion, while the other generates the quantum correlations responsible for the entanglement.

The most significant aspect is that the correlations do not remain confined inside the cavity: they are transferred to the light that exits and propagates through space. In this way, the motion of the nanoparticle — a localised quantum system — is linked to a light field that can carry information to another location. It is precisely this connection between “stationary” and “flying” systems that makes the result relevant for future quantum networks.

To verify the entanglement, the researchers measured the light exiting the cavity using heterodyne detection and reconstructed the correlations between the optical field and the nanosphere’s motion. The parameter used to certify entanglement falls below the separability threshold of 1, reaching an experimental minimum of 0.918 ± 0.029. The effect is also sustained over a frequency range exceeding 40 kHz, demonstrating good robustness under operating conditions.

An important feature of the experiment is that it operates under steady-state conditions at room temperature, without requiring cryogenic cooling. This makes levitated optomechanical systems particularly promising for the transfer and storage of quantum states.

More broadly, controlling quantum phenomena in increasingly massive objects may provide new tools for exploring the boundary between the quantum and macroscopic worlds — and, in the longer term, for addressing fundamental questions such as the possible quantum nature of gravity.

Reference: Q. Deplano et al.; Science (2026). DOI: 10.1126/science.aeh1375

For a divulgative article see ScienceAlert.