A glass nanosphere stays quantum-entangled with light at room temperature
A glass nanosphere’s motion remained quantum-entangled with light leaving an optical cavity at room temperature. Two lasers performed different tasks: one cooled and stabilized motion, while the other generated quantum correlations. The work has now appeared in Science after a February preprint. The experiment concerns sustained entanglement between matter and light; it does not demonstrate a working quantum computer.
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A whole glass sphere’s motion became entangled
A glass sphere about 100 nanometres across has been kept quantum-entangled with light at room temperature. Researchers at Italy’s University of Florence and the National Institute of Optics observed the connection between the sphere’s motion and light leaving an optical cavity. The work appeared in Science after its preprint was published in February. The quantum behavior concerned the motion of the whole sphere, containing tens of millions of atoms.[1], [2]
An optical tweezer, a tightly focused laser beam, suspended the sphere between two facing mirrors that formed the cavity. With no attachment to a surface, the particle oscillated around its equilibrium position. A near-vacuum chamber isolated this movement from environmental disturbances that could erase the fragile quantum behavior.[1]
Two laser colors shared cooling and entanglement
Two lasers performed complementary tasks within one two-color optical tweezer. Red-detuned light cooled and stabilized the sphere’s oscillations; blue-detuned light generated entanglement between the motion and light. The cooling targeted the particular mechanical motion under study. The surrounding laboratory remained at room temperature, without cooling the entire apparatus to cryogenic temperatures. The experiment ran for hours while three laser systems remained stable as the chamber reached sufficiently low pressure.[1]
Entanglement linked the sphere’s position and momentum with light properties analogous to amplitude and phase. Measuring the outgoing light let the team reconstruct those correlations. Results crossed the threshold separating entangled systems from systems describable independently, and stayed on the entangled side when experimental uncertainty and different analysis assumptions were included. The entanglement was stable across a frequency band wider than 40 kilohertz.[1], [2]
Outgoing light carries the quantum correlations
Corresponding author Francesco Marin, a professor of experimental condensed-matter physics, said the correlations persisted in light propagating beyond the cavity. That light could in principle travel through an optical network or interact with another quantum device.[1], [2]
The team’s next research objectives include stronger entanglement and dynamic control. Co-author Quentin Deplano described a possible quantum memory that would store information carried by light and release it later. Writing and retrieving quantum information in the mechanical system, and connecting several nanospheres, remain research goals. The experiment does not demonstrate a working quantum computer.[1], [2]
