224 research outputs found
Use of dynamical coupling for improved quantum state transfer
We propose a method to improve quantum state transfer in transmission lines.
The idea is to localize the information on the last qubit of a transmission
line, by dynamically varying the coupling constants between the first and the
last pair of qubits. The fidelity of state transfer is higher then in a chain
with fixed coupling constants. The effect is stable against small fluctuations
in the system parameters.Comment: 5 pages, 7 figure
Role of interference in quantum state transfer through spin chains
We examine the role that interference plays in quantum state transfer through
several types of finite spin chains, including chains with isotropic Heisenberg
interaction between nearest neighbors, chains with reduced coupling constants
to the spins at the end of the chain, and chains with anisotropic coupling
constants. We evaluate quantitatively both the interference corresponding to
the propagation of the entire chain, and the interference in the effective
propagation of the first and last spins only, treating the rest of the chain as
black box. We show that perfect quantum state transfer is possible without
quantum interference, and provide evidence that the spin chains examined
realize interference-free quantum state transfer to a good approximation.Comment: 10 figure
Efficiency of Grinding and Mechanical Activation of Solids in Planetary Ball Mills
We develop the algorithm of the procedure for determin-ing the efficiency of operation of planetary mills which is based on the analysis of the movement of the entire load(balls and material) in drums, with the calculation of energy and frequency characteristics of the interaction between milling bodies and material under treatment. We describe the procedure of determination of the efficient power input consumed for driving the ball load of a plane-tary mill and thus for performing the work of grinding and mechanical activation of the material, and some practical examples of industrial applications of planetary-type mills
Quantum state transfer in arrays of flux qubits
In this work, we describe a possible experimental realization of Bose's idea
to use spin chains for short distance quantum communication [S. Bose, {\it
Phys. Rev. Lett.} {\bf 91} 207901]. Josephson arrays have been proposed and
analyzed as transmission channels for systems of superconducting charge qubits.
Here, we consider a chain of persistent current qubits, that is appropriate for
state transfer with high fidelity in systems containing flux qubits. We
calculate the fidelity of state transfer for this system. In general, the
Hamiltonian of this system is not of XXZ-type, and we analyze the magnitude and
the effect of the terms that don't conserve the z-component of the total spin.Comment: 10 pages, 8 figure
1-(3,5-Dichlorophenyl)-1H-1,2,3,4-tetrazole
In the title compound, C7H4Cl2N4, the dihedral angle between the tetrazole and benzene rings is 17.2 (2)°. In the crystal, C—H⋯N interactions link the molecules into a flattened helical chain along the b axis
1-(4-Chlorophenyl)-1H-1,2,3,4-tetrazole
There are two independent molecules in the asymmetric unit of the title compound, C7H5ClN4, in which the tetrazole and benzene rings are twisted by dihedral angles of 12.9 (1) and 39.8 (1)°. In the crystal, the independent molecules are connected into a tetramer by C—H⋯N hydrogen bonds, generating an R
4
4(12) graph-set motif
Lost photon enhances superresolution
Quantum imaging can beat classical resolution limits, imposed by diffraction
of light. In particular, it is known that one can reduce the image blurring and
increase the achievable resolution by illuminating an object by entangled light
and measuring coincidences of photons. If an -photon entangled state is used
and the th-order correlation function is measured, the point-spread function
(PSF) effectively becomes times narrower relatively to classical
coherent imaging. Quite surprisingly, measuring -photon correlations is not
the best choice if an -photon entangled state is available. We show that for
measuring -photon coincidences (thus, ignoring one of the available
photons), PSF can be made even narrower. This observation paves a way for a
strong conditional resolution enhancement by registering one of the photons
outside the imaging area. We analyze the conditions necessary for the
resolution increase and propose a practical scheme, suitable for observation
and exploitation of the effect
Algorithmic approach to linearization of scalar ordinary differential equation
Аналитическая теория дифференциальных уравнени
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