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Physics Encyclopedia Entry 1778028784

** Quantum entanglement is a fundamental concept 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. **CONTENT:** ## Overview Quantum entanglement is a phenomenon that has fascinated physicists for nearly a century. It is a key feature of **quantum mechanics**, the branch of physics that describes the behavior of matter and energy at the smallest scales. Entanglement occurs when two or more particles interact in such a way that their properties become correlated, meaning that the state of one particle cannot be described independently of the others. This phenomenon has been experimentally confirmed numerous times and has been shown to occur even when the particles are separated by large distances, a phenomenon known as **quantum non-locality**. The concept of entanglement was first introduced by **Albert Einstein**, **Boris Podolsky**, and **Nathan Rosen** in 1935, in a thought experiment known as the **EPR paradox**. They proposed that if two particles were entangled in such a way that the state of one particle was correlated with the state of the other, then it would be possible to instantaneously transmit information between the two particles, violating the principles of **special relativity**. However, this idea was later shown to be incorrect, and entanglement is now understood to be a fundamental aspect of quantum mechanics. ## History/Background The concept of entanglement has its roots in the early days of quantum mechanics. In the 1920s and 1930s, physicists such as **Louis de Broglie** and **Erwin Schrödinger** began to develop the mathematical framework of quantum mechanics, which included the concept of wave functions and **superposition**. However, it was not until the 1960s that the concept of entanglement began to take shape. In 1964, **John Stewart Bell** published a paper that showed that entanglement was a fundamental aspect of quantum mechanics, and that it could be used to test the principles of quantum mechanics. ## Key Information Entanglement is a fundamental aspect of quantum mechanics, and it has been experimentally confirmed numerous times. Some of the key features of entanglement include: * **Quantum non-locality**: Entanglement allows for instantaneous communication between particles, even when they are separated by large distances. * **Correlation**: The state of one particle is correlated with the state of the other, meaning that the state of one particle cannot be described independently of the other. * **Superposition**: Entangled particles can exist in a superposition of states, meaning that they can have multiple properties simultaneously. * **Entanglement swapping**: Entanglement can be transferred from one particle to another, even if they are not directly interacting. ## Significance Entanglement is a fundamental aspect of quantum mechanics, and it has far-reaching implications for our understanding of the universe. Some of the key significance of entanglement includes: * **Quantum computing**: Entanglement is a key feature of quantum computing, and it is used to perform calculations that are exponentially faster than classical computers. * **Quantum cryptography**: Entanglement is used to create secure communication channels, known as **quantum key distribution**. * **Quantum teleportation**: Entanglement is used to transfer information from one particle to another, without physical transport of the particles themselves. * **Fundamental understanding of the universe**: Entanglement provides a fundamental understanding of the behavior of matter and energy at the smallest scales, and it has implications for our understanding of the universe as a whole. **INFOBOX:** - Name: Quantum Entanglement - Type: Quantum Mechanical Phenomenon - Date: 1935 (EPR paradox) - Location: Theoretical (quantum mechanics) - Known For: Fundamental aspect of quantum mechanics, key feature of quantum computing and quantum cryptography **TAGS:** Quantum Mechanics, Entanglement, Quantum Non-Locality, Superposition, Quantum Computing, Quantum Cryptography, Quantum Teleportation, Quantum Key Distribution.