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Ermakov–Lewis Invariant
Many quantum mechanical Hamiltonians are time dependent. Methods to solve problems where there is an explicit time dependence is an open subject nowadays. It is important to look for constants of motion or invariants for problems of this kind. For the (time dependent) harmonic oscillator it is possible to write several invariants, among them, the Ermakov–Lewis invariant which is developed below. The time dependent harmonic oscillator Hamiltonian reads : \hat =\frac\left hat^2+\Omega^2(t)\hat^2\right It is well known that an invariant for this type of interaction has the form : \hat=\frac\left \left( \frac\right) ^+(\rho\hat-\dot\hat)^\right where \rho obeys the Ermakov equation : \ddot+\Omega^\rho=\rho^. The above invariant is the so-called Ermakov–Lewis invariant. It is easy to show that \hat may be related to the time independent harmonic oscillator Hamiltonian via a unitary transformation of the form : \hat=e^e^= e^ e^, as :\frac\left hat^2+\hat^2\right\hat\hat\hat^. Th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hamiltonian (quantum Mechanics)
Hamiltonian may refer to: * Hamiltonian mechanics, a function that represents the total energy of a system * Hamiltonian (quantum mechanics), an operator corresponding to the total energy of that system ** Dyall Hamiltonian, a modified Hamiltonian with two-electron nature ** Molecular Hamiltonian, the Hamiltonian operator representing the energy of the electrons and nuclei in a molecule * Hamiltonian (control theory), a function used to solve a problem of optimal control for a dynamical system * Hamiltonian path, a path in a graph that visits each vertex exactly once * Hamiltonian group, a non-abelian group the subgroups of which are all normal * Hamiltonian economic program, the economic policies advocated by Alexander Hamilton, the first United States Secretary of the Treasury See also * Alexander Hamilton (1755 or 1757–1804), American statesman and one of the Founding Fathers of the US * Hamilton (other) Hamilton may refer to: People * Hamilton (name), a common ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Invariants
In the mathematical field of knot theory, a quantum knot invariant or quantum invariant of a knot or link is a linear sum of colored Jones polynomial of surgery presentations of the knot complement. List of invariants *Finite type invariant * Kontsevich invariant * Kashaev's invariant * Witten–Reshetikhin–Turaev invariant ( Chern–Simons) *Invariant differential operator *Rozansky–Witten invariant * Vassiliev knot invariant *Dehn invariant *LMO invariant *Turaev–Viro invariant *Dijkgraaf–Witten invariant *Reshetikhin–Turaev invariant *Tau-invariant *I-Invariant * Klein J-invariant *Quantum isotopy invariant * Ermakov–Lewis invariant *Hermitian invariant *Goussarov–Habiro theory of finite-type invariant *Linear quantum invariant (orthogonal function invariant) *Murakami–Ohtsuki TQFT * Generalized Casson invariant * Casson-Walker invariant *Khovanov–Rozansky invariant *HOMFLY polynomial *K-theory invariants *Atiyah–Patodi–Singer eta invariant * Link invar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Harmonic Oscillator
In classical mechanics, a harmonic oscillator is a system that, when displaced from its Mechanical equilibrium, equilibrium position, experiences a restoring force ''F'' Proportionality (mathematics), proportional to the displacement ''x'': \vec F = -k \vec x, where ''k'' is a positive coefficient, constant. If ''F'' is the only force acting on the system, the system is called a simple harmonic oscillator, and it undergoes simple harmonic motion: sinusoidal oscillations about the equilibrium point, with a constant amplitude and a constant frequency (which does not depend on the amplitude). If a frictional force (Damping ratio, damping) proportional to the velocity is also present, the harmonic oscillator is described as a damped oscillator. Depending on the friction coefficient, the system can: * Oscillate with a frequency lower than in the Damping ratio, undamped case, and an amplitude decreasing with time (Damping ratio, underdamped oscillator). * Decay to the equilibrium p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time
Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to compare the duration of events or the intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience. Time is often referred to as a fourth dimension, along with three spatial dimensions. Time has long been an important subject of study in religion, philosophy, and science, but defining it in a manner applicable to all fields without circularity has consistently eluded scholars. Nevertheless, diverse fields such as business, industry, sports, the sciences, and the performing arts all incorporate some notion of time into their respective measuring systems. 108 pages. Time in physics is operationally defined as "what a clock reads". The physical nature of time is addre ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quantum Invariant
In the mathematical field of knot theory, a quantum knot invariant or quantum invariant of a knot or link is a linear sum of colored Jones polynomial of surgery presentations of the knot complement. List of invariants *Finite type invariant *Kontsevich invariant * Kashaev's invariant * Witten–Reshetikhin–Turaev invariant ( Chern–Simons) *Invariant differential operator *Rozansky–Witten invariant * Vassiliev knot invariant *Dehn invariant *LMO invariant *Turaev–Viro invariant *Dijkgraaf–Witten invariant *Reshetikhin–Turaev invariant *Tau-invariant *I-Invariant * Klein J-invariant *Quantum isotopy invariant * Ermakov–Lewis invariant *Hermitian invariant *Goussarov–Habiro theory of finite-type invariant *Linear quantum invariant (orthogonal function invariant) *Murakami–Ohtsuki TQFT * Generalized Casson invariant * Casson-Walker invariant *Khovanov–Rozansky invariant *HOMFLY polynomial *K-theory invariants *Atiyah–Patodi–Singer eta invariant * Link invariant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Unitary Transformation
In mathematics, a unitary transformation is a transformation that preserves the inner product: the inner product of two vectors before the transformation is equal to their inner product after the transformation. Formal definition More precisely, a unitary transformation is an isomorphism between two inner product spaces (such as Hilbert spaces). In other words, a ''unitary transformation'' is a bijective function U : H \to H_2\, between two inner product spaces, H and H_2, such that \langle Ux, Uy \rangle_ = \langle x, y \rangle_ \quad \text x, y \in H. Properties A unitary transformation is an isometry, as one can see by setting x=y in this formula. Unitary operator In the case when H_1 and H_2 are the same space, a unitary transformation is an automorphism of that Hilbert space, and then it is also called a unitary operator. Antiunitary transformation A closely related notion is that of antiunitary transformation, which is a bijective function :U:H_1\to H_2\, between two co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Schrödinger Equation
The Schrödinger equation is a linear partial differential equation that governs the wave function of a quantum-mechanical system. It is a key result in quantum mechanics, and its discovery was a significant landmark in the development of the subject. The equation is named after Erwin Schrödinger, who postulated the equation in 1925, and published it in 1926, forming the basis for the work that resulted in his Nobel Prize in Physics in 1933. Conceptually, the Schrödinger equation is the quantum counterpart of Newton's second law in classical mechanics. Given a set of known initial conditions, Newton's second law makes a mathematical prediction as to what path a given physical system will take over time. The Schrödinger equation gives the evolution over time of a wave function, the quantum-mechanical characterization of an isolated physical system. The equation can be derived from the fact that the time-evolution operator must be unitary, and must therefore be generated by t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Exponential Function
The exponential function is a mathematical function denoted by f(x)=\exp(x) or e^x (where the argument is written as an exponent). Unless otherwise specified, the term generally refers to the positive-valued function of a real variable, although it can be extended to the complex numbers or generalized to other mathematical objects like matrices or Lie algebras. The exponential function originated from the notion of exponentiation (repeated multiplication), but modern definitions (there are several equivalent characterizations) allow it to be rigorously extended to all real arguments, including irrational numbers. Its ubiquitous occurrence in pure and applied mathematics led mathematician Walter Rudin to opine that the exponential function is "the most important function in mathematics". The exponential function satisfies the exponentiation identity e^ = e^x e^y \text x,y\in\mathbb, which, along with the definition e = \exp(1), shows that e^n=\underbrace_ for positive i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Squeeze Operator
In quantum physics, the squeeze operator for a single mode of the electromagnetic field is :\hat(z) = \exp \left ( (z^* \hat^2 - z \hat^) \right ) , \qquad z = r \, e^ where the operators inside the exponential are the ladder operators. It is a unitary operator and therefore obeys S(\zeta)S^\dagger (\zeta)=S^\dagger (\zeta)S(\zeta)=\hat 1, where \hat 1 is the identity operator. Its action on the annihilation and creation operators produces :\hat^(z)\hat\hat(z)=\hat\cosh r - e^ \hat^ \sinh r \qquad\text\qquad \hat^(z)\hat^\hat(z)=\hat^\cosh r - e^ \hat \sinh r The squeeze operator is ubiquitous in quantum optics and can operate on any state. For example, when acting upon the vacuum, the squeezing operator produces the squeezed vacuum state. The squeezing operator can also act on coherent states and produce squeezed coherent states. The squeezing operator does not commute with the displacement operator: : \hat(z) \hat(\alpha) \neq \hat(\alpha) \hat(z), nor does it commute ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quadrupole Ion Trap
A quadrupole ion trap or paul trap is a type of ion trap that uses dynamic electric fields to trap charged particles. They are also called radio frequency (RF) traps or Paul traps in honor of Wolfgang Paul, who invented the device and shared the Nobel Prize in Physics in 1989 for this work. It is used as a component of a mass spectrometer or a trapped ion quantum computer. Overview A charged particle, such as an atomic or molecular ion, feels a force from an electric field. It is not possible to create a static configuration of electric fields that traps the charged particle in all three directions (this restriction is known as Earnshaw's theorem). It is possible, however, to create an ''average'' confining force in all three directions by use of electric fields that change in time. To do so, the confining and anti-confining directions are switched at a rate faster than it takes the particle to escape the trap. The traps are also called "radio frequency" traps because the switc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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