Laser theory with natural inclusion of radiation loss: Density-operator approach

1988 ◽  
Vol 66 (9) ◽  
pp. 764-768 ◽  
Author(s):  
A. Liberato ◽  
B. Baseia
Keyword(s):  
Recent Result ◽  
Density Operator ◽  
Conventional Treatment ◽  
Optical Cavity ◽  
Equation Of Motion ◽  
Operator Approach ◽  
Transmitted Beam ◽  
Laser Theory ◽  
Natural Inclusion ◽  
Natural Way

A recent result of a previous paper describing the field loss in an optical cavity in a natural way is applied to laser theory. The field loss, due to the transmitted beam light, and the field gain, now attributed to the presence of active atoms but previously attributed to two noninteracting mechanisms, are correctly added to provide the equation of motion for the density operator of the radiation field. The replacement of individual operators, which appear in the conventional treatment, with collective operators is a conceptual difference that emerges from the present approach.

Dissipative systems: on the natural inclusion of radiation loss in the quantized electromagnetic field

1987 ◽  
Vol 65 (4) ◽  
pp. 359-364 ◽  
Author(s):  
B. Baseia ◽  
F. J. B. Feitosa ◽  
A. Liberato
Keyword(s):  
Electromagnetic Field ◽  
Initial Conditions ◽  
Optical Cavity ◽  
Radiation Loss ◽  
Dissipative Systems ◽  
Mixed States ◽  
Natural Inclusion ◽  
Quantized Electromagnetic Field ◽  
Quantized Radiation Field ◽  
Natural Way

The inclusion of damping in the quantized radiation field in pure and mixed states is accomplished in a natural way, without using traditional loss reservoirs, through the application of appropriate boundary conditions in a simple model of an optical cavity coupled to the outside world. By using collective operators (which are suitable weighted superpositions of the usual creation and annihilation operators for modes of the continuous spectrum, extended over each Fox–Li band) and convenient initial conditions, we are able to describe the radiation loss from an optical cavity to the outside world. The physical situations corresponding to initial conditions leading to the exponential damping are also investigated.

Combo separability criteria and lower bound on concurrence

2021 ◽  
Author(s):  
Zangi Sultan ◽  
Jiansheng Wu ◽  
Cong-Feng Qiao
Keyword(s):  
Lower Bound ◽  
Correlation Matrix ◽  
Density Operator ◽  
Singular Values ◽  
Quantum Information Theory ◽  
Separability Criteria ◽  
The Given ◽  
Ky Fan ◽  
Natural Way ◽  
Extract Information

Abstract Detection and quantification of entanglement are extremely important in quantum information theory. We can extract information by using the spectrum or singular values of the density operator. The correlation matrix norm deals with the concept of quantum entanglement in a mathematically natural way. In this work, we use Ky Fan norm of the Bloch matrix to investigate the disentanglement of quantum states. Our separability criterion not only unifies some well-known criteria but also leads to a better lower bound on concurrence. We explain with an example how the entanglement of the given state is missed by existing criteria but can be detected by our criterion. The proposed lower bound on concurrence also has advantages over some investigated bounds.

scholarly journals Nonequilibrium density operator approach to domain wall resistivity

2011 ◽  
Vol 286 ◽  
pp. 012017 ◽  
Author(s):  
Jun-ichiro Kishine ◽  
A S Ovchinnikov ◽  
I V Proskurin
Keyword(s):  
Domain Wall ◽  
Density Operator ◽  
Operator Approach ◽  
Wall Resistivity

Quantum Statistical Derivation of the Ginzburg–Landau Equation.

1998 ◽  
Vol 12 (01) ◽  
pp. 99-111 ◽  
Author(s):  
Shigeji Fujita ◽  
Salvador Godoy
Keyword(s):  
Density Operator ◽  
Cooper Pair ◽  
Energy Gap ◽  
Landau Equation ◽  
Field Operator ◽  
Equation Of Motion ◽  
Condensation Energy ◽  
Ginzburg Landau ◽  
Quantum Statistical ◽  
New Formula

The Cooper pair (pairon) field operator ψ†(r,t) changes, following Heisenberg's equation of motion. If the Hamiltonian ℋ contains pairon kinetic energies h0, a condensation energy α(<0) and a repulsive point-like interpairon interaction βδ(r1-r2), β>0, the evolution equation for ψ is nonlinear, from which we obtain the Ginzburg–Landau (GL) equation: [Formula: see text] for the GL wave function Ψσ(r)≡ <r| n1/2|σ>, where σ denotes the state of the condensed pairons, and n the density operator. The GL equation with α=-εg(T) is shown to hold for all temperatures (T) below Tc, where εg is the pairon energy gap. Its equilibrium solution yields that the condensed pairon density n0(T)=|Ψσ(r)|2 is proportional to εg(T). The original GL T-dependence of the expansion parameters near Tc:α=-b(Tc-T), β= constant is justified. With the assumption of h0, a new formula for the penetration depth is obtained.

scholarly journals Application of the method of asymptotic homogenization to an acoustic metafluid

2011 ◽  
Vol 467 (2135) ◽  
pp. 3318-3331 ◽  
Author(s):  
John D. Smith
Keyword(s):  
Material Properties ◽  
Effective Properties ◽  
Low Frequency ◽  
Equation Of Motion ◽  
Effective Equation ◽  
Asymptotic Homogenization ◽  
Effective Wave ◽  
Dynamic Effective Properties ◽  
Anisotropic Stiffness ◽  
Natural Way

The method of asymptotic homogenization is used to find the dynamic effective properties of a metamaterial consisting of two alternating layers of fluid, repeating periodically. As well as the effective wave equation, the method gives the effective equation of motion and constitutive relation in a natural way. When the material properties are such that resonant effects can be present in one of the layers, it is found that the metamaterial changes dynamically from a metafluid with anisotropic density and isotropic stiffness at low frequency to one with anisotropic stiffness when the frequency is near to one of the local resonances. In this region of frequency, the resulting metamaterial is not a pentamode material and thus does not belong to the class of metafluids that can be transformed to an isotropic fluid by a coordinate transformation.

scholarly journals Faraday effect in graphene enclosed in an optical cavity and the equation of motion method for the study of magneto-optical transport in solids

2011 ◽  
Vol 84 (23) ◽  
Author(s):  
Aires Ferreira ◽  
J. Viana-Gomes ◽  
Yu. V. Bludov ◽  
V. Pereira ◽  
N. M. R. Peres ◽  
...  
Keyword(s):  
Faraday Effect ◽  
Optical Cavity ◽  
Equation Of Motion ◽  
Optical Transport ◽  
Motion Method
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