On the theory of magnetic field dependence of heat conductivity in dielectric in isotropic model

Phonon polarization in a magnetic field is analyzed in isotropic model. It is shown, that at presence of spin-phonon interaction phonon possess circular polari-zation which causes the appearance of heat flux component perpendicular both to temperature gradient and magnetic field.Comment: 5 pages, 0 figure

Hellmann and Feynman theorem versus diffusion Monte Carlo experiment

In a computer experiment the choice of suitable estimators to measure a physical quantity plays an important role. We propose a new direct route to determine estimators for observables which do not commute with the Hamiltonian. Our new route makes use of the Hellmann and Feynman theorem and in a diffusion Monte Carlo simulation it introduces a new bias to the measure due to the choice of the auxiliary function. This bias is independent from the usual one due to the choice of the trial wave function. We used our route to measure the radial distribution function of a spin one half Fermion fluid.Comment: 7 pages, 1 figure, 1 tabl

Electrically controlling single spin qubits in a continuous microwave field

Large-scale quantum computers must be built upon quantum bits that are both highly coherent and locally controllable. We demonstrate the quantum control of the electron and the nuclear spin of a single 31P atom in silicon, using a continuous microwave magnetic field together with nanoscale electrostatic gates. The qubits are tuned into resonance with the microwave field by a local change in electric field, which induces a Stark shift of the qubit energies. This method, known as A-gate control, preserves the excellent coherence times and gate fidelities of isolated spins, and can be extended to arbitrarily many qubits without requiring multiple microwave sources.Comment: Main paper: 13 pages, 4 figures. Supplementary information: 25 pages, 13 figure

Meson and Quark Degrees of Freedom and the Radius of the Deuteron

The existing experimental data for the deuteron charge radius are discussed. The data of elastic electron scattering are inconsistent with the value obtained in a recent atomic physics experiment. Theoretical predictions based on a nonrelativistic description of the deuteron with realistic nucleon-nucleon potentials and with a rather complete set of meson-exchange contributions to the charge operator are presented. Corrections arising from the quark-gluon substructure of the nucleon are explored in a nonrelativistic quark model; the quark-gluon corrections, not accounted for by meson exchange, are small. Our prediction for the deuteron charge radius favors the value of a recent atomic physics experiment.Comment: 20 pages, LaTeX, 4 Postscript figures, to appear in Few-Body-System