Instantaneous communication does not occur between two entangled particles, even if they are separated by large distances. The phenomenon you are referring to is known as quantum entanglement.
Quantum entanglement is a phenomenon where two or more particles become correlated in such a way that the state of one particle is dependent on the state of the other(s), regardless of the distance between them. When two particles are entangled, their properties become entangled as well. This means that measuring the state of one particle instantaneously affects the state of the other, no matter how far apart they are.
However, it is important to note that quantum entanglement does not allow for faster-than-light communication or transfer of information. The correlation between entangled particles is a non-local phenomenon, meaning that the entangled particles do not communicate with each other in the traditional sense. Instead, their states are linked in a way that is not explainable by classical physics.
When one measures the state of an entangled particle, it collapses into a definite state, and the state of the other entangled particle also collapses instantaneously, even if it is light-years away. However, this collapse is random and unpredictable, and no information is transmitted between the particles. It is only through subsequent comparisons of measurement results that correlations between the entangled particles can be observed.
The phenomenon of entanglement is still not fully understood, and its interpretation is a subject of ongoing scientific research and debate. But it is clear that it does not violate the principle of causality or allow for superluminal communication.