Florence physicists entangle a levitating glass speck with light at room temperature

Physicists at the University of Florence and Italy’s National Institute of Optics (CNR-INO) say they have generated stationary quantum entanglement between the centre-of-mass motion of a levitated glass nanosphere and light that leaves the experiment — all while the laboratory stays at room temperature.

The team, led by Francesco Marin with co-authors Quentin Deplano, Antonio Pontin and Francesco Marino, trapped a roughly 100-nanometre silica sphere — tens of millions of atoms — in an optical tweezer inside a near-vacuum cavity, ScienceAlert and a CNR release reported around Oct. 1–2. A red-detuned laser cooled and stabilised the bead’s tiny oscillations toward the quantum regime; a blue-detuned companion created the correlations that link the sphere’s position and momentum to the light’s amplitude and phase “quadratures.” Measurements of the outgoing field drove a separability parameter to 0.918 ± 0.029, below the classical threshold of 1, confirming entanglement that persists in propagating light rather than only in cavity-trapped modes.

That travelling field is the practical prize. Marin told ScienceAlert that cavity-bound light is hard to use as a quantum resource elsewhere, whereas light that exits can, in principle, feed networks, remote measurements or other devices. The work, published in Science (doi: 10.1126/science.aeh1375) and mirrored on arXiv, did not cryogenically cool the apparatus; levitation, high vacuum and optical cooling alone kept the mechanical degree of freedom cold enough for quantum correlations to form before environmental heating erased them. CNR-INO’s Francesco Marino called the result a step toward using massive room-temperature oscillators as quantum memories that store and release information carried by light.

Canadian labs working on quantum networks and sensing will watch the next milestones: stronger, dynamically controlled entanglement and coupling several nanospheres into larger systems. The Florence–CNR experiment does not claim a quantum computer; it claims a cleaner interface between a macroscopic mechanical object and a flying optical channel — a building block, not a finished machine.

Sources: ScienceAlert; CNR / Università di Firenze; arXiv — Stationary entanglement of a levitated oscillator with an optical field; INSPIRE-HEP record.