In quantum theory, measurement refers to the process of obtaining information about a quantum system. When it comes to entangled particles, measurement plays a crucial role in understanding their behavior and the correlations that exist between them.
When two particles are entangled, their quantum states become intertwined in such a way that the state of one particle is dependent on the state of the other, regardless of the spatial separation between them. This entanglement leads to what Einstein famously referred to as "spooky action at a distance."
The concept of instantaneous transfer of information between entangled particles is often misunderstood. In quantum theory, information cannot be transferred faster than the speed of light, which is a fundamental principle of relativity. Therefore, it is incorrect to interpret entanglement as a means of instant communication or transfer of data.
What makes entanglement puzzling is that the measurement of one entangled particle can instantaneously affect the state of the other, even when they are separated by vast distances. This phenomenon is known as quantum non-locality. However, it's important to note that this non-local influence cannot be used to transmit information or signals faster than the speed of light.
The nature of this non-local influence is still a topic of ongoing research and debate in quantum physics. One interpretation is that the measurement of one particle collapses its quantum state, which in turn affects the state of the other particle. This collapse is probabilistic, meaning the measurement outcome is only determined upon measurement and is not predetermined.
In summary, measurement in the context of entangled particles refers to the act of obtaining information about their quantum states. While entanglement allows for correlations between particles, it does not enable the instantaneous transfer of information or communication between them. The measurement outcomes of entangled particles are probabilistic and cannot be used for faster-than-light communication.