For a long time, physicists were certain: quantum entanglement requires direct quantum contact. A new study refutes this. Two microscopic magnetic particles, connected only by a classical spring, successfully become entangled. The spring oscillates strictly according to Newton's laws, without any quantum weirdness, but its behavior surprisingly resembles the curved space around massive bodies. Thus, simple mechanics becomes an analogue of gravity. Calculations confirmed genuine entanglement. To measure it, entropy is used — a measure of disorder. And in the hybrid system, it increased exactly to the same level as with quantum contact. The classical spring performed like an ideal quantum channel. This result overturns the conviction that only quantum objects can transmit entanglement. This discovery challenges experiments that seek the quantum nature of gravity through particle entanglement. If a classical pendulum yields the same picture, then classical gravity can also 'glue' matter at the quantum level. It turns out that Einstein's idea that gravity is purely classical is not so wrong after all. It recalls the story of gravitational waves: long considered merely a mathematical abstraction, until they were detected.
Entanglement is measured via entropy — a measure of disorder. In the spring system, this entropy increased just as it would if the mediator were quantum. The classical spring performed just as well as the most perfect quantum channel.