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History Of Atomic, Molecular, And Optical Physics Atomic, molecular, and optical physics Atomic, molecular, and optical physics (AMO) is the study of mattermatter and lightmatter interactions; at the scale of one or a few atoms [1] and energy scales around several electron volts.[2]:1356[3] The three areas are closely interrelated. AMO theory includes classical, semiclassical and quantum treatments [...More...]  "History Of Atomic, Molecular, And Optical Physics" on: Wikipedia Yahoo Parouse 

Quantum Mechanics Quantum mechanics (QM; also known as quantum physics or quantum theory), including quantum field theory, is a fundamental theory in physics which describes nature at the smallest scales of energy levels of atoms and subatomic particles.[2] Classical physics Classical physics (the physics existing before quantum mechanics) is a set of fundamental theories which describes nature at ordinary (macroscopic) scale [...More...]  "Quantum Mechanics" on: Wikipedia Yahoo Parouse 

Scattering Theory In mathematics and physics, scattering theory is a framework for studying and understanding the scattering of waves and particles. Wave scattering corresponds to the collision and scattering of a wave with some material object, for instance sunlight scattered by rain drops to form a rainbow. Scattering Scattering also includes the interaction of billiard balls on a table, the Rutherford scattering Rutherford scattering (or angle change) of alpha particles by gold nuclei, the Bragg scattering (or diffraction) of electrons and Xrays by a cluster of atoms, and the inelastic scattering of a fission fragment as it traverses a thin foil. More precisely, scattering consists of the study of how solutions of partial differential equations, propagating freely "in the distant past", come together and interact with one another or with a boundary condition, and then propagate away "to the distant future" [...More...]  "Scattering Theory" on: Wikipedia Yahoo Parouse 

Quantum System A quantum system is a portion of the whole Universe Universe (environment or physical world) which is taken under consideration to make analysis or to study for quantum mechanics pertaining to the waveparticle duality in that system. Everything outside this system (i.e. environment) is studied only to observe its effects on the system. A quantum system involves the wave function and its constituents, such as the momentum and wavelength of the wave for which wave function is being defined. See also[edit]Quantum Twostate quantum system Nonlinear system Dynamical system Thermodynamic system Physical system Quantum state Quantum number Ground state Excited state Energy levels Degenerate energy levelsThis quantum mechanicsrelated article is a stub [...More...]  "Quantum System" on: Wikipedia Yahoo Parouse 

Quantum State In quantum physics, quantum state refers to the state of an isolated quantum system. A quantum state provides a probability distribution for the value of each observable, i.e. for the outcome of each possible measurement on the system. Knowledge of the quantum state together with the rules[clarification needed] for the system's evolution in time exhausts all that can be predicted about the system's behavior. A mixture of quantum states is again a quantum state. Quantum states that cannot be written as a mixture of other states are called pure quantum states, all other states are called mixed quantum states. Mathematically, a pure quantum state can be represented by a ray in a Hilbert space Hilbert space over the complex numbers.[1] The ray is a set of nonzero vectors differing by just a complex scalar factor; any of them can be chosen as a state vector to represent the ray and thus the state [...More...]  "Quantum State" on: Wikipedia Yahoo Parouse 

Quantum Number Quantum numbers describe values of conserved quantities in the dynamics of a quantum system. In the case of electrons, the quantum numbers can be defined as "the sets of numerical values which give acceptable solutions to the Schrödinger wave equation for the hydrogen atom". An important aspect of quantum mechanics is the quantization of observable quantities, since quantum numbers are discrete sets of integers or halfintegers, although they could approach infinity in some cases. This distinguishes quantum mechanics from classical mechanics where the values that characterize the system such as mass, charge, or momentum, range continuously. Quantum numbers often describe specifically the energy levels of electrons in atoms, but other possibilities include angular momentum, spin, etc [...More...]  "Quantum Number" on: Wikipedia Yahoo Parouse 

Quantum Noise In physics, quantum noise refers to the uncertainty of a physical quantity that is due to its quantum origin. In certain situations, quantum noise appears as shot noise; for example, most optical communications use amplitude modulation, and thus, the quantum noise appears as shot noise only. For the case of uncertainty in the electric field in some lasers, the quantum noise is not just shot noise; uncertainties of both amplitude and phase contribute to the quantum noise. This issue becomes important in the case of noise of a quantum amplifier, which preserves the phase [...More...]  "Quantum Noise" on: Wikipedia Yahoo Parouse 

Quantum Fluctuation In quantum physics, a quantum fluctuation (or vacuum state fluctuation or vacuum fluctuation) is the temporary change in the amount of energy in a point in space,[1] as explained in Werner Heisenberg's uncertainty principle. This allows the creation of particleantiparticle pairs of virtual particles. The effects of these particles are measurable, for example, in the effective charge of the electron, different from its "naked" charge. Quantum fluctuations may have been very important in the origin of the structure of the universe: according to the model of expansive inflation the ones that existed when inflation began were amplified and formed the seed of all current observed structure [...More...]  "Quantum Fluctuation" on: Wikipedia Yahoo Parouse 

Quantum Foam Quantum foam (also referred to as spacetime foam) is a concept in quantum mechanics devised by John Wheeler in 1955.[1]Contents1 Background 2 Experimental results2.1 Constraints and limits2.1.1 Random diffusion model 2.1.2 Holographic model3 Relation to other theories 4 See also 5 Notes 6 ReferencesBackground[edit] With an incomplete theory of quantum gravity, it is impossible to be certain what spacetime would look like at small scales. However, there is no reason that spacetime needs to be fundamentally smooth [...More...]  "Quantum Foam" on: Wikipedia Yahoo Parouse 

Heisenberg Uncertainty Principle In quantum mechanics, the uncertainty principle (also known as Heisenberg's uncertainty principle) is any of a variety of mathematical inequalities[1] asserting a fundamental limit to the precision with which certain pairs of physical properties of a particle, known as complementary variables, such as position x and momentum p, can be known. Introduced first in 1927, by the German physicist Werner Heisenberg, it states that the more precisely the position of some particle is determined, the less precisely its momentum can be known, and vice versa.[2] The formal inequality relating the standard deviation of position σx and the standard deviation of momentum σp was derived by Earle Hesse Kennard[3] later that year and by Hermann Weyl[4] in 1928: σ x σ p ≥ ℏ 2 displaystyle sigma _ x sigma _ p geq frac [...More...]  "Heisenberg Uncertainty Principle" on: Wikipedia Yahoo Parouse 

Photon Entanglement Photon Photon entanglement is a supplement to the article BohrEinstein debates and is designed to help clarify the discussion of the EinsteinPodolskyRosen argument in quantum theory which takes place in the previous article.Contents1 Entanglement 2 Applications 3 See also 4 References 5 External linksEntanglement[edit] A quantum system is described, at every instant, by a vector state which, according to the theory, represents the maximum amount of information that it is possible to have. To simplify discussion, taking the example of the state of polarization of a photon and associate with it the vector state 45 ⟩ displaystyle left45rightrangle The knowledge of the vector state, in fact, provides us exclusively with information on the possible results of measurements which we decide to carry out on the system [...More...]  "Photon Entanglement" on: Wikipedia Yahoo Parouse 

Spontaneous Parametric Downconversion Spontaneous parametric downconversion Spontaneous parametric downconversion (also known as SPDC, or parametric scattering) is an important process in quantum optics, used especially as a source of entangled photon pairs, and of single photons.Contents1 Basic process 2 Example 3 History 4 Applications 5 Alternatives 6 See also 7 ReferencesBasic process[edit]An SPDC scheme with the Type I outputPlay mediaThe video of an experiment showing vacuum fluctuations (in the red ring) amplified by SPDC (corresponding to the image above)A nonlinear crystal is used to split photon beams into pairs of photons that, in accordance with the law of conservation of energy and law of conservation of momentum, have combined energies and momenta equal to the energy and momentum of the original photon and crystal lattice, are phasematched in the frequency domain, and have correlated polarizations. The state of the crystal is unchanged by the process [...More...]  "Spontaneous Parametric Downconversion" on: Wikipedia Yahoo Parouse 

Spin (physics) In quantum mechanics and particle physics, spin is an intrinsic form of angular momentum carried by elementary particles, composite particles (hadrons), and atomic nuclei.[1][2] Spin is one of two types of angular momentum in quantum mechanics, the other being orbital angular momentum. The orbital angular momentum operator is the quantummechanical counterpart to the classical angular momentum of orbital revolution: it arises when a particle executes a rotating or twisting trajectory (such as when an electron orbits a nucleus).[3][4] The existence of spin angular momentum is inferred from experiments, such as the Stern–Gerlach experiment, in which particles are observed to possess angular momentum that cannot be accounted for by orbital angular momentum alone.[5] In some ways, spin is like a vector quantity; it has a definite magnitude, and it has a "direction" (but quantization makes this "direction" different from the direction of an ordinary vector) [...More...]  "Spin (physics)" on: Wikipedia Yahoo Parouse 

Symmetry In Quantum Mechanics Symmetries in quantum mechanics describe features of spacetime and particles which are unchanged under some transformation, in the context of quantum mechanics, relativistic quantum mechanics and quantum field theory, and with applications in the mathematical formulation of the standard model and condensed matter physics. In general, symmetry in physics, invariance, and conservation laws, are fundamentally important constraints for formulating physical theories and models. In practice, they are powerful methods for solving problems and predicting what can happen [...More...]  "Symmetry In Quantum Mechanics" on: Wikipedia Yahoo Parouse 

Quantum Superposition Quantum superposition is a fundamental principle of quantum mechanics. It states that, much like waves in classical physics, any two (or more) quantum states can be added together ("superposed") and the result will be another valid quantum state; and conversely, that every quantum state can be represented as a sum of two or more other distinct states [...More...]  "Quantum Superposition" on: Wikipedia Yahoo Parouse 

Symmetry Breaking This article needs attention from an expert in Physics. Please add a reason or a talk parameter to this template to explain the issue with the article. WikiProject Physics may be able to help recruit an expert. (May 2014)A ball is initially located at the top of the central hill (C). This position is an unstable equilibrium: a very small perturbation will cause it to fall to one of the two stable wells left (L) or (R). Even if the hill is symmetric and there is no reason for the ball to fall on either side, the observed final state is not symmetric.In physics, symmetry breaking is a phenomenon in which (infinitesimally) small fluctuations acting on a system crossing a critical point decide the system's fate, by determining which branch of a bifurcation is taken. To an outside observer unaware of the fluctuations (or "noise"), the choice will appear arbitrary [...More...]  "Symmetry Breaking" on: Wikipedia Yahoo Parouse 