Magnetic field dip and the lifetime of the spherical tensor element of the density matrix in a He-Ne laser

1984 ◽  
Vol 31 (3) ◽  
pp. 259-263 ◽  
Author(s):  
Kazuo Kuroda ◽  
Yoshihiro Kawase ◽  
Iwao Ogura
Keyword(s):  
Magnetic Field ◽  
Density Matrix ◽  
Tensor Element

scholarly journals The Chandrasekhar Mass of A Gravitating Electron Crystal

1994 ◽  
Vol 147 ◽  
pp. 565-570
Author(s):  
D. Engelhardt ◽  
I. Bues
Keyword(s):  
Magnetic Field ◽  
Density Matrix ◽  
White Dwarf ◽  
Matrix Formalism ◽  
Plasma Zone ◽  
Isothermal Model ◽  
Fermi Function ◽  
Density Matrix Formalism ◽  
The Magnetic Field ◽  
Electron Crystal

AbstractThe internal structure of a white dwarf may be changed by a strong magnetic field. A local model of the electrons is constructed within a thermal density matrix formalism, essentially a Heisenberg magnetism model. This results in a matrix Fermi function which is used to construct an isothermal model of the electron crystal. The central density of the crystal is 108kg/m3 independent of the magnetic field within the plasma and therefore lower than the relativistic density, whereas this density is constant until the Fermi momentum x f = 0.3 * me * c. Chandrasekhar masses up to 1.44 * 1.4M0 are possible for polarizations of the plasma zone lower than 0.5, if the temperature is close to the Curie point, whereas the crystal itself destabilizes the white dwarf dependent on temperature.

The diamagnetism of quasi-bound conduction electrons

1953 ◽  
Vol 49 (2) ◽  
pp. 292-298 ◽  
Author(s):  
A. H. Wilson
Keyword(s):  
Magnetic Field ◽  
Partition Function ◽  
Power Series ◽  
Density Matrix ◽  
Complete Solution ◽  
Exact Expression ◽  
Free Electrons ◽  
Conduction Electrons ◽  
Image Position ◽  
Bound Electrons

The diamagnetism of the conduction electrons gives rise to some of the most difficult problems in the theory of metals, the complete solution of which has not yet been found. Formally, the problem is equivalent to determining the density matrixand the exact expression for ψ(r′, r, γ) for perfectly free electrons in a constant magnetic field H has recently been found by Sondheimer and Wilson(2). The extension of the theory to deal with quasi-bound electrons for all values of H seems to be out of the question, but an approximate partition function was given by Peierls (1), excluding terms of higher order than H2. In The theory of metals ((3), referred to as T.M.) I gave a more powerful and simpler method of dealing with the problem, based upon the properties of ψ(r′, r, γ), but since the solution was obtained as a power series in μ0Hγ, where it could at best determine only the normal diamagnetism.

Using solitons for manipulating qubits

2014 ◽  
Vol 12 (02) ◽  
pp. 1461013 ◽  
Author(s):  
Alessandro Cuccoli ◽  
Davide Nuzzi ◽  
Ruggero Vaia ◽  
Paola Verrucchi
Keyword(s):  
Magnetic Field ◽  
Solid State ◽  
Density Matrix ◽  
Time Dependence ◽  
Magnetic Moment ◽  
Spin Chain ◽  
Quantum Object ◽  
Spin Magnetic Moment ◽  
Quantum Devices ◽  
Nonlinear Excitations

Many proposals for quantum devices are based on qubits that are physically realized by the spin magnetic moment of some quantum object. In this case, one of the most often adopted strategies for manipulating qubits is that of using external magnetic fields. However, selectively applying a field just to one qubit may be a practically unattainable goal, as it is, for instance, in most solid-state based setups. In this work, we present a proposal for using nonlinear excitations of solitonic type to accomplish the above task. Our scheme entails the generation of a dynamical soliton in a classical spin-chain which is locally coupled with one qubit: as the soliton runs through, the qubit behaves, due to its interaction with the chain, as if it were subject to a magnetic field with a time dependence that follows from the soliton's features. We here present results for the time evolution of the qubit density-matrix induced by the overall dynamics of the above scheme.

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