10,004 research outputs found
Effects of depolarizing quantum channels on BB84 and SARG04 quantum cryptography protocols
We report experimental studies on the effect of the depolarizing quantum
channel on weak-pulse BB84 and SARG04 quantum cryptography. The experimental
results show that, in real world conditions in which channel depolarization
cannot be ignored, BB84 should perform better than SARG04.Comment: 4 pages, 4 figure
Predominance of the Kitaev interaction in a three-dimensional honeycomb iridate: from ab-initio to spin model
The recently discovered three-dimensional hyperhoneycomb iridate,
-LiIrO, has raised hopes for the realization of dominant Kitaev
interaction between spin-orbit entangled local moments due to its near-ideal
lattice structure. If true, this material may lie close to the sought-after
quantum spin liquid phase in three dimensions. Utilizing ab-initio electronic
structure calculations, we first show that the spin-orbit entangled basis,
=1/2, correctly captures the low energy electronic structure. The
effective spin model derived in the strong coupling limit supplemented by the
ab-initio results is shown to be dominated by the Kitaev interaction. We
demonstrated that the possible range of parameters is consistent with a
non-coplanar spiral magnetic order found in a recent experiment. All of these
analyses suggest that -LiIrO may be the closest among known
materials to the Kitaev spin liquid regime.Comment: 9 pages, 6 figures, 2 table
Object-oriented construction of a multigrid electronic-structure code with Fortran 90
We describe the object-oriented implementation of a higher-order
finite-difference density-functional code in Fortran 90. Object-oriented models
of grid and related objects are constructed and employed for the implementation
of an efficient one-way multigrid method we have recently proposed for the
density-functional electronic-structure calculations. Detailed analysis of
performance and strategy of the one-way multigrid scheme will be presented.Comment: 24 pages, 6 figures, to appear in Comput. Phys. Com
Experimental verification of the commutation relation for Pauli spin operators using single-photon quantum interference
We report experimental verification of the commutation relation for Pauli
spin operators using quantum interference of the single-photon polarization
state. By superposing the quantum operations and on a single-photon polarization state, we have experimentally
implemented the commutator, , and the anticommutator,
, and have demonstrated the relative phase factor
of between and operations. The
experimental quantum operation corresponding to the commutator, , showed process fidelity of 0.94 compared to the ideal
operation and is determined to be .Comment: 4pages, 3 figure
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