Introduction
Quantum physics, also known as quantum mechanics, is a branch of physics that deals with the behavior and properties of particles at the atomic and subatomic level. It is different from classical physics in that it incorporates the principles of wave-particle duality, superposition, and entanglement, which allow for phenomena not seen in the macroscopic world.
Key Concepts
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Wave-particle duality: In quantum mechanics, particles such as electrons and photons exhibit both wave-like and particle-like properties. They can interfere and diffract like waves, but also interact with other particles as if they were localized particles. This duality is captured by the wave function, which describes the possible states of a quantum system and the probability of finding a particle in each state.
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The wave function: The wave function, often denoted by the Greek letter psi (Ψ), describes the probability distribution of a particle’s position, momentum, and other properties. The wave function evolves according to the Schrödinger equation, which is a fundamental equation in quantum mechanics. The square of the magnitude of the wave function at a given point represents the probability density of finding the particle at that location.
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Superposition: Particles in a quantum state can exist in multiple states at once, as a linear combination of different wave functions. This is called superposition. When a measurement is made on a quantum system in a superposition of states, the system collapses into one of the possible states, with the probability of each outcome determined by the coefficients in the linear combination.
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Quantum entanglement: Two or more particles can become entangled, meaning that the properties of one particle are dependent on the properties of the other, even when separated by large distances. This phenomenon, which Albert Einstein famously called “spooky action at a distance,” is explained by the fact that the wave function describing the entangled particles cannot be separated into individual wave functions for each particle. Entanglement is an essential concept in quantum computing and quantum communication.
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The Heisenberg Uncertainty Principle: The uncertainty principle, formulated by Werner Heisenberg, states that certain pairs of observables, such as position and momentum or energy and time, cannot be simultaneously measured with arbitrary precision. The more precisely one of the quantities is known, the less precisely the other can be determined. This principle is a direct consequence of the wave-like nature of quantum particles.
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Quantum tunneling: Due to their wave-like nature, particles in quantum mechanics can “tunnel” through energy barriers that would be insurmountable in classical physics. This tunneling phenomenon is responsible for many important processes, such as radioactive decay and the behavior of electrons in semiconductors.