What is Quantum Entanglement?
Quantum entanglement is a phenomenon in quantum mechanics where two or more particles become interconnected such that the quantum state of each particle cannot be described independently, even when separated by vast distances. This principle, first highlighted by Einstein, Podolsky, and Rosen in 1935, demonstrates that measuring one particle's property instantly determines the other's, challenging classical notions of locality and realism.
Key Principles of Entanglement
The foundational principles include superposition, where entangled particles exist in multiple states simultaneously until measured; non-locality, allowing instantaneous correlations without physical signals; and the conservation of quantum properties like spin or polarization. These principles are governed by the Schrödinger equation and confirmed through Bell's theorem experiments, which rule out local hidden variables.
Practical Example: EPR Paradox and Experiments
Consider two entangled electrons with opposite spins. Measuring one as 'up' instantly sets the other to 'down,' regardless of distance. Alain Aspect's 1982 experiments verified this by closing detection loopholes, showing correlations stronger than classical limits, as predicted by quantum theory.
Importance and Applications in Modern Physics
Quantum entanglement underpins technologies like quantum teleportation, where information is transferred via entangled particles, and quantum cryptography for unbreakable encryption. It drives quantum computing by enabling qubits to process data in parallel, revolutionizing fields from drug discovery to secure global networks, while deepening our understanding of the universe's fundamental interconnectedness.