Entanglement is a phenomenon in quantum mechanics where two or more particles become correlated in such a way that the state of one particle is linked to the state of another, regardless of the distance between them. This correlation persists even when the particles are separated by vast distances, and any change in the state of one particle instantaneously affects the state of the other, which is known as "non-locality."
However, it is important to note that entanglement cannot be used for instantaneous communication. The non-local influence between entangled particles cannot be exploited to transmit information faster than the speed of light. This is due to the no-communication theorem, which prohibits the use of entanglement for faster-than-light communication.
Adding a control or switch to entanglement would not alter the fundamental limitations imposed by the no-communication theorem. While it is possible to manipulate the state of an entangled particle, the changes would not be observable until a measurement is made, and the observed results would still obey the principles of quantum mechanics, including the limitations on information transfer.
Entanglement is a complex and fascinating aspect of quantum mechanics, and its properties are still being explored and researched. While it has practical applications in areas such as quantum computing and cryptography, it does not provide a means for faster-than-light communication or the reversal of the arrow of time.