ENCYCLOPEDIA ENTRY
Correlated recognition events maintained by ledger accounting across arbitrary spatial separations.
Quantum entanglement is a fundamental phenomenon in quantum physics, characterized by the correlation of quantum states between particles, regardless of the distance separating them. This correlation is maintained through a conceptual ledger that accounts for recognition events across arbitrary spatial separations.
Quantum entanglement occurs when two or more particles become interconnected in such a way that the state of one particle cannot be described independently of the state of the other(s), even when the particles are separated by large distances. Mathematically, this can be expressed as:
For two entangled particles, the joint state can be represented as:
|\Psi\rangle = \alpha |00\rangle + \beta |11\rangle
where |00⟩ and |11⟩ are the basis states of the two particles, and α and β are complex coefficients that satisfy the normalization condition |α|² + |β|² = 1.
Imagine you have two coins that are entangled. If you flip one coin and it lands on heads, the other coin will instantly show tails, no matter how far apart they are. This strange connection between the coins is what we mean by quantum entanglement. It defies our everyday understanding of how objects should behave, as it suggests that information can be shared instantly across distances, challenging our notions of locality.
Quantum entanglement is crucial for the development of quantum technologies, including quantum computing and quantum cryptography. It enables secure communication methods that are theoretically immune to eavesdropping and allows for the creation of powerful quantum computers that can solve complex problems much faster than classical computers.
When particles interact in such a way that their quantum states become linked, they enter an entangled state. This can happen through various processes, such as particle collisions or the decay of a particle into two entangled particles. Once entangled, measuring the state of one particle will immediately affect the state of the other, regardless of the distance between them. This phenomenon is often illustrated through the concept of a "ledger," where the outcomes of measurements are recorded and correlated across space.
Entangled states can be mathematically described using the formalism of quantum mechanics. For example, the Bell states are specific examples of maximally entangled states:
|\Phi^+\rangle = \frac{1}{\sqrt{2}} (|00\rangle + |11\rangle)
|\Phi^-\rangle = \frac{1}{\sqrt{2}} (|00\rangle - |11\rangle)
|\Psi^+\rangle = \frac{1}{\sqrt{2}} (|01\rangle + |10\rangle)
|\Psi^-\rangle = \frac{1}{\sqrt{2}} (|01\rangle - |10\rangle)
Quantum entanglement is closely related to other concepts in quantum mechanics, such as superposition and quantum interference. It also plays a significant role in quantum teleportation and the Einstein-Podolsky-Rosen (EPR) paradox, which questions the completeness of quantum mechanics.
Experiments such as the Bell test experiments have been conducted to test the predictions of quantum entanglement. These experiments aim to demonstrate the violation of Bell's inequalities, providing evidence for the non-local nature of entangled particles.
One common misconception is that entangled particles communicate with each other. In reality, the correlation between their states is established at the moment of entanglement, and no information is transmitted between them after that point.
Classical correlation can be explained by classical physics and does not involve instantaneous effects over distances. In contrast, entanglement involves quantum states that are interdependent in a way that cannot be explained by classical physics.
No, while entangled particles exhibit correlated behavior, they cannot be used to transmit information faster than light. The outcomes of measurements are random, and the correlation only becomes apparent when the results are compared after the fact.