The phenomenon of entanglement in quantum mechanics is indeed intriguing and has been experimentally verified. When two particles become entangled, their quantum states become correlated in such a way that measuring one particle's state can provide information about the state of the other, regardless of the distance between them. This correlation exists even if the particles are spatially separated and have experienced no physical disturbance or interaction after their entanglement was established.
The measurement of one entangled particle does appear to have an instantaneous effect on the other entangled particle, which can seem to violate our classical intuition of causality and locality. This non-local correlation is what led Albert Einstein, Boris Podolsky, and Nathan Rosen to propose their famous EPR (Einstein-Podolsky-Rosen) paradox in 1935, which aimed to challenge the completeness of quantum mechanics.
However, it's important to note that the phenomenon of entanglement does not provide a direct demonstration or explanation of wavefunction collapse. Wavefunction collapse refers to the transition from a superposition of possible states to a definite state during a measurement. Entanglement, on the other hand, describes the correlation between the quantum states of two or more particles.
In the case of entanglement, when one particle is measured, its wavefunction does indeed appear to "collapse" to a definite state. However, this does not imply that wavefunction collapse is caused by a physical interaction between the two particles. The correlation between entangled particles is a fundamental property of quantum mechanics, and it does not require any physical signal or interaction to instantaneously affect the other particle's state.
The nature of entanglement and its relationship to wavefunction collapse remains a subject of ongoing research and debate. Various interpretations and mathematical formalisms have been proposed to explain and understand these phenomena. While entanglement does provide fascinating insights into the non-classical nature of quantum mechanics, its specific connection to the collapse of the wavefunction is still an area of active investigation and discussion among physicists.