Quantum entanglement is a phenomenon in quantum mechanics where two or more particles become correlated in such a way that the state of one particle cannot be described independently of the others. This correlation persists even when the particles are separated by large distances, defying classical intuitions about locality.
In quantum mechanics, particles are described by their quantum states, which are represented by mathematical objects called wavefunctions. When particles become entangled, their individual wavefunctions become intertwined, forming a composite or joint wavefunction that describes the system as a whole.
The precise mechanism by which particles become entangled is still a topic of ongoing research and investigation. However, entanglement is often generated through interactions between particles, such as collisions or interactions with external fields.
Once particles become entangled, their states become correlated in a way that cannot be explained by classical concepts. This correlation is characterized by what is known as entanglement entropy, which quantifies the degree of entanglement between the particles.
It's important to note that entanglement itself does not require any physical force or interaction to maintain the correlation between the particles. Instead, the entangled state is a fundamental property of the system that persists until it is measured or otherwise disturbed.
When one of the entangled particles is measured, its state becomes determined, and as a consequence, the state of the other particle becomes instantly determined as well. This instantaneous correlation, often referred to as "spooky action at a distance," is a unique feature of entanglement in quantum mechanics and has been experimentally verified.
The concept of entanglement is a foundational aspect of quantum mechanics, and it plays a crucial role in various phenomena and applications, including quantum computing, quantum communication, and tests of fundamental physics principles.