This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Today, many physicists are actively exploring how light could be used to link objects through quantum entanglement. By fully harnessing the effect, they hope to unlock a wide array of applications, from secure communication networks spanning vast distances to sensitive new tests of the fundamental laws of physics.
Through new research published in Science, a team led by Francesco Marin at the University of Florence has taken an important step toward this goal by entangling the motion of a tiny levitating glass sphere with light, without needing to cool their experiment to ultralow temperatures. When two quantum particles become entangled, their properties are so deeply intertwined that neither can be fully described without the other. However, this delicate link is easily broken by tiny disturbances from the surrounding environment and becomes ever harder to protect as objects grow larger.
In previous experiments, researchers have created brief bursts of entanglement between photons and vibrating macroscopic particles, but only at temperatures close to absolute zero. More recently, physicists have recognized that tiny glass spheres levitated by light could offer a promising alternative, since they float almost completely isolated from their surroundings. In their study, Marin's team explored this idea using a glass sphere just 100 nanometers across.
They held the sphere in a tightly focused laser beam called an "optical tweezer," positioned between two facing mirrors inside a near-vacuum chamber. On its own, the light needed to create entanglement also tended to induce unwanted oscillations in the sphere, eventually knocking it out of its trap. To solve this, the researchers combined two lasers of slightly different colors.
The first cooled and steadied the sphere's back-and-forth motion, while the second was free to entangle this movement with the light. As the sphere oscillated, information about its motion became imprinted on the light leaving the mirrors. By measuring this light over many hours, Marin's team reconstructed the full pattern of connections between the sphere's motion and the light.
Even when the surrounding lab was at room temperature, their measured correlations crossed a mathematical threshold confirming that the two had become genuinely entangled. Crucially, the entanglement persisted in light traveling away from the mirrors. Marin's team now hopes to strengthen the entanglement through refined experimental techniques and to control it actively rather than simply observe it.
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