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In probability theory, an "expectation value" is the average of all values of a measurable quantity that one would expect, if a measurement was repeated a large number of times on a given system. For example, for an unbiased coin, the expectation value for "heads" is half of all tosses.
Each measurable quantity of a quantum system has an operator that, when mathematically applied to the system, gives a value of that quantity for that system. The expectation value for that quantity, for a given quantum system, is the product of that operator on a given state of the system, times the probability of the system being in that state, integrated over all possible states of the system. A more formally stated example:
For a quantum state Ψ(x), where 'x' can vary from -∞ to ∞, and for which Q(x) is a measurable quantity, then the expectation value of Q(x) would be equal to
∫Ψ*(x)Ψ(x)Q(x)dx
integrated from x = -∞ to x = ∞
As an example, suppose we wanted the expectation value for the radial position of an electron in its '1S' state within a hydrogen atom. When doing the formal math, we find that this value exactly equals the Bohr Radius. In contrast to the Bohr Model of an atom, this expectration value does NOT state that this electron IS at this radius, only that an AVERAGE of all radial measurements of such an electron would be the Bohr Radius.
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EzraIn quantum mechanics, the expectation value is the average value of a physical quantity obtained from a wave function. It represents the most probable outcome of measuring that quantity for a given quantum state. Mathematically, it is calculated by taking the integral of the observable operator over the wave function squared.
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What is a mixed state in quantum mechanics?
The mixed state in quantum mechanics is the statistical ensemble of the pure states.
What is the alternative to quantum mechanics?
Classical mechanics is the alternative to quantum mechanics. It is a branch of physics that describes the motion of macroscopic objects using principles established by Isaac Newton. Unlike quantum mechanics, classical mechanics assumes that objects have definite positions and velocities at all times.
What do people say about future research concerning quantum mechanics?
People often discuss future research in quantum mechanics as focusing on developing practical quantum technologies like quantum computing, communication, and sensing. Some also highlight the need to better understand fundamental aspects of quantum mechanics, such as the nature of entanglement and the interpretation of quantum phenomena. Additionally, there is growing interest in exploring the implications of quantum mechanics for fields like artificial intelligence, materials science, and cryptography.
When did werner heisenberg discover the quantum theory?
Werner Heisenberg developed the quantum theory in 1925 as part of his work on matrix mechanics. His groundbreaking research contributed to the foundation of quantum mechanics and earned him the Nobel Prize in Physics in 1932.
What is the Alternative to the Quantum Mechanics theory?
One alternative to the standard quantum mechanics theory is the pilot-wave theory, also known as Bohmian mechanics. This theory proposes that particles have definite positions and trajectories, guided by a wave function. It aims to provide a deterministic account of quantum phenomena without relying on wavefunction collapse.
