Quantum entanglement is a phenomenon in which two or more particles become correlated in such a way that the state of one particle is intrinsically connected to the state of the other, even when they are physically separated. This correlation holds regardless of the distance between the particles, and any change to one particle's state instantaneously affects the state of the other particle, regardless of the distance between them. This non-local correlation is what makes quantum entanglement intriguing.
However, despite the apparent instantaneous connection between entangled particles, it is important to note that quantum entanglement cannot be used for faster-than-light communication or transmitting information. This limitation arises due to the principles of quantum mechanics and the no-communication theorem.
The no-communication theorem, formulated by physicist Asher Peres and others, states that it is impossible to use quantum entanglement to transmit information faster than the speed of light. This theorem is a consequence of two key aspects of quantum mechanics:
No-cloning theorem: According to the no-cloning theorem, it is impossible to make an identical copy of an unknown quantum state. This means that it is not possible to take an unknown state of one entangled particle and reproduce it exactly on another particle without disturbing the original state.
Measurement collapse: When a measurement is made on an entangled particle, the superposition of states collapses into a definite state. However, the specific outcome of the measurement is random and cannot be controlled or manipulated to transmit information.
These principles prevent the use of quantum entanglement for faster-than-light communication. While a measurement on one entangled particle instantaneously affects the state of the other particle, the outcome of that measurement is unpredictable. Therefore, it is not possible to use entangled particles to transmit information in a controlled manner.
It's worth noting that quantum entanglement has practical applications in quantum information processing, such as quantum teleportation and quantum cryptography. However, these applications do not violate the no-communication theorem since they rely on shared pre-established information or the transmission of classical information through traditional channels.
In summary, while quantum entanglement exhibits non-local correlations between particles, it cannot be exploited to transmit information faster than the speed of light due to the principles of quantum mechanics and the no-communication theorem.