Overview

Quantum entanglement is a physical phenomenon that occurs when a group of particles is generated, interact, or share spatial proximity in a way such that the quantum state of each particle of the group cannot be described independently of the state of the others, including when the particles are separated by a large distance.

The more I study quantum physics, the more it seems that the universe is not only stranger than we imagine, it is stranger than we can imagine.

First experimentally observed in 1935, entanglement has since become a foundational resource in quantum information science, enabling protocols such as quantum teleportation, superdense coding, and quantum key distribution.[1]

Mathematical Description

In the formalism of quantum mechanics, an entangled state cannot be written as a tensor product of individual particle states. For two qubits \(A\) and \(B\), a maximally entangled state (Bell state) is given by:

|Ψ⟩ = (|00⟩ + |11⟩) / √2

Measuring particle A instantaneously determines the state of particle B, regardless of distance. This non-local correlation does not violate special relativity, as no usable information is transmitted faster than light.[2]