How to Test Whether Gravity Is Quantum express
Two tiny diamonds float in a vacuum, separated by a distance that light cannot cross during the experiment. Inside each, like a frozen spark, resides an entangled spin — a quantum state linking them into a single whole. Now the diamonds begin to move, but not just any motion: each one seems to split, existing in two places at once. This is not a trick but a spatial superposition — the heart of a new experiment designed to answer the question: is gravity quantum?
The spins inside the diamonds (for instance, NV-center defects) are already entangled, but that is not enough. Their motion generates gravitational fields, and if gravity is truly quantum, those fields will also become entangled. What arises is what is called an EPR state of spacetime curvature — a connection so deep that measuring one field instantly affects the other.
The scientists propose to make measurements only on the gravitational fields, leaving the diamonds untouched. This is a clever move: it eliminates any loopholes related to locality (no signal can peek at its neighbor). If the results show a correlation that cannot be explained by any 'clever' classical theory, then gravity will be caught behaving quantum mechanically. The experiment would require objects of micron size, cooled to near absolute zero, like dust motes in a beam of light, but incredibly cold and precise.
Entanglement is like a pair of dice that always land on the same number, even if thrown on different planets, but in the quantum world, this is not cheating; it is a fundamental property.
In the novel 'The Quantum Thief' by Hannu Rajaniemi, gravity is used as a tool to transmit information through entangled states, blurring the line between space and data.