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Physics Encyclopedia Entry 1775828946

** This encyclopedia entry is about the fundamental concept of **Quantum Entanglement**, 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, even when separated by large distances. ## Overview Quantum Entanglement is a fundamental aspect of **Quantum Mechanics**, a branch of physics that describes the behavior of matter and energy at the smallest scales. It was first proposed by **Albert Einstein**, **Boris Podolsky**, and **Nathan Rosen** in 1935, as a thought experiment to demonstrate the apparent absurdity of **Quantum Mechanics**. However, their work ultimately led to a deeper understanding of the phenomenon, which has been experimentally confirmed numerous times since then. Quantum Entanglement is often described as a "spooky action at a distance," where the state of one particle is instantaneously affected by the state of another particle, regardless of the distance between them. This phenomenon challenges our classical understanding of space and time, and has significant implications for our understanding of the universe. ## History/Background The concept of Quantum Entanglement was first proposed by Einstein, Podolsky, and Rosen in their 1935 paper, "Can Quantum-Mechanical Description of Physical Reality be Considered Complete?" They argued that if two particles were entangled, measuring the state of one particle would instantaneously affect the state of the other particle, regardless of the distance between them. This seemed to imply that information could travel faster than the speed of light, which was considered impossible according to the theory of **Special Relativity**. However, in 1964, physicist **John Bell** showed that Quantum Entanglement was not just a theoretical concept, but a real phenomenon that could be experimentally verified. Bell's theorem, which was later experimentally confirmed, demonstrated that Quantum Entanglement was a fundamental aspect of Quantum Mechanics, and could not be explained by classical physics. ## Key Information Quantum Entanglement has been experimentally confirmed numerous times since Bell's theorem. Some of the key experiments include: * **Aspect's Experiment** (1982): Physicist **Alain Aspect** performed an experiment that demonstrated the reality of Quantum Entanglement, and showed that it was not just a statistical phenomenon. * **Quantum Eraser Experiment** (1999): Physicists **Zeilinger** and **Walther** performed an experiment that demonstrated the ability to "erase" the entanglement between two particles, and showed that the information was not lost. * **Entanglement Swapping** (1999): Physicists **Zeilinger** and **Walther** also demonstrated the ability to transfer entanglement between two particles, without physical contact between them. Quantum Entanglement has significant implications for our understanding of the universe, and has led to the development of new technologies, such as: * **Quantum Computing**: Quantum Entanglement is a key feature of Quantum Computing, which has the potential to revolutionize computing and cryptography. * **Quantum Teleportation**: Quantum Entanglement is also a key feature of Quantum Teleportation, which allows for the transfer of information from one particle to another, without physical transport of the particles themselves. ## Significance Quantum Entanglement is a fundamental aspect of Quantum Mechanics, and has significant implications for our understanding of the universe. It challenges our classical understanding of space and time, and has led to the development of new technologies, such as Quantum Computing and Quantum Teleportation. INFOBOX: - Name: Quantum Entanglement - Type: Quantum Mechanical Phenomenon - Date: 1935 (Einstein, Podolsky, and Rosen's paper) - Location: Theoretical, but experimentally confirmed in various locations - Known For: Demonstrating the reality of Quantum Mechanics, and leading to the development of new technologies TAGS: Quantum Mechanics, Quantum Entanglement, Quantum Computing, Quantum Teleportation, Entanglement Swapping, Quantum Eraser Experiment, Aspect's Experiment, Bell's Theorem, Special Relativity, Albert Einstein, Boris Podolsky, Nathan Rosen, John Bell, Alain Aspect, Anton Zeilinger, Anton Walther.