476 research outputs found
Chain of Superconducting Loops as a Possible Quantum Register
The idea of the quantum computation is based on paradoxical principles of
quantum physics, superposition and entanglement of quantum states. This idea
looks well-founded on the microscopic level in spite of the absence of an
universally recognized interpretation of these paradoxical principles since
they were corroborated over and over again by reliable experiments on the
microscopic level. But the technology can not be able in the near future to
work on the microscopic level. Therefore macroscopic quantum phenomenon -
superconductivity is very attractive for the realization of the idea of quantum
computer. It is shown in the present paper that a chain of superconducting
loops can be only possible quantum register. The proposals by some authors to
provide the EPR correlation with help of a classical interaction witness the
misunderstanding of the entanglement essence. The problem of the possibility of
superposition of macroscopically distinct states is considered.Comment: 10 pages, 0 figure. Presented at International Symposium "Quantum
Informatics 2004" Moscow, October 5-8, 200
RKKY interaction in Layered Superconductors with Anisotropic Pairing
The RKKY interaction between rare-earth (RE) ions in high-
superconductors is considered at . It is shown that this interaction
consists of two terms: conventional oscillating one and the positive term,
which is proportional to the gap function and decreases in the case
inversely proportional to the distance. In the antiferromagnetic state of the
RE subsystem this positive interaction gives rise for frustrations which
diminishes the Neel temperature. In the case of strongly anisotropic gap
function this frustration produces two different values of the effective
nearest neighbor exchange coupling between RE ions along the and . This
anisotropy has been established experimentally in Ref.\cite{6,7,8}.Comment: 10 pages, REVTEX, no figure
Transport of interacting electrons through a potential barrier: nonperturbative RG approach
We calculate the linear response conductance of electrons in a Luttinger
liquid with arbitrary interaction g_2, and subject to a potential barrier of
arbitrary strength, as a function of temperature. We first map the Hamiltonian
in the basis of scattering states into an effective low energy Hamiltonian in
current algebra form. Analyzing the perturbation theory in the fermionic
representation the diagrams contributing to the renormalization group (RG)
\beta-function are identified. A universal part of the \beta-function is given
by a ladder series and summed to all orders in g_2. First non-universal
corrections beyond the ladder series are discussed. The RG-equation for the
temperature dependent conductance is solved analytically. Our result agrees
with known limiting cases.Comment: 6 pages, 5 figure
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