40,711 research outputs found
Grover's search algorithm: An optical approach
The essential operations of a quantum computer can be accomplished using
solely optical elements, with different polarization or spatial modes
representing the individual qubits. We present a simple all-optical
implementation of Grover's algorithm for efficient searching, in which a
database of four elements is searched with a single query. By `compiling' the
actual setup, we have reduced the required number of optical elements from 24
to only 12. We discuss the extension to larger databases, and the limitations
of these techniques.Comment: 6 pages, 5 figures. To appear in a special issue of the Journal of
Modern Optics -- "The Physics of Quantum Information
Cl electrosorption on Ag(100): Lateral interactions and electrosorption valency from comparison of Monte Carlo simulations with chronocoulometry experiments
We present Monte Carlo Simulations using an equilibrium lattice-gas model for
the electrosorption of Cl on Ag(100) single-crystal surfaces. Fitting the
simulated isotherms to chronocoulometry experiments, we extract parameters such
as the electrosorption valency gamma and the next-nearest-neighbor lateral
interaction energy phi_nnn. Both coverage-dependent and coverage independent
gamma were previously studied assuming a constant phi_nnn [I. Abou Hamad, Th.
Wandlowski, G. Brown, P.A. Rikvold, J. Electroanal. Chem. 554-555 (2003) 211].
Here, a self-consistent, entirely electrostatic picture of the lateral
interactions with a coverage-dependent phi_nnn is developed, and a relationship
between phi_nnn and gamma is investigated for Cl on Ag(100).Comment: Accepted for publication in Electrochimica Acta, 10 pages, 7 figures,
2 tables and an appendi
Long-range Ni/Mn structural order in epitaxial double perovskite La2NiMnO6 thin films
We report and compare the structural, magnetic, and optical properties of
ordered La2NiMnO6 thin films and its disordered LaNi0.5Mn0.5O3 counterpart. An
x-ray diffraction study reveals that the B-site Ni/Mn ordering induces
additional XRD reflections as the crystal symmetry is transformed from a
pseudocubic perovskite unit cell in the disordered phase to a monoclinic form
with larger lattice parameters for the ordered phase. Polarized Raman
spectroscopy studies reveal that the ordered samples are characterized by
additional phonon excitations that are absent in the disordered phase. The
appearance of these additional phonon excitations is interpreted as the
clearest signature of Brillouin zone folding as a result of the long-range
Ni/Mn ordering in La2NiMnO6. Both ordered and disordered materials display a
single ferromagnetic-to-paramagnetic transition. The ordered films display also
a saturation magnetization close to 4.8 mB/f.u. and a transition temperature
(FM-TC) around 270 K, while the disordered ones have only a 3.7 mB/f.u.
saturation magnetization and a FM-TC around 138 K. The differences in their
magnetic behaviours are understood based on the distinct local electronic
configurations of their Ni/Mn cations.Comment: 15 pages, 5 fig
Phase formation, phonon behavior, and magnetic properties of novel ferromagnetic La3BAlMnO9 (B = Co or Ni) triple perovskites
In the quest for novel magnetoelectric materials, we have grown, stabilized
and explored the properties of La3BAlMnO9 (B = Co or Mn) thin films. In this
paper, we report the influence of the growth parameters that promote B/Al/Mn
ordering in the pseudo-cubic unit cell and their likely influence on the
magnetic and multiferroic properties. The temperature dependence of the
magnetization shows that La3CoAlMnO9 is ferromagnetic up to 190 K while
La3NiAlMnO9 shows a TC of 130 K. The behavior of these films are compared and
contrasted with related La2BMnO6 double perovskites. It is observed that the
insertion of AlO6 octahedra between CoO6 and MnO6 suppresses significantly the
strength of the superexchange interaction, spin-phonon and spin-polar coupling.Comment: 13 pages, 3 fig
100 MHz Amplitude and Polarization Modulated Optical Source for Free-Space Quantum Key Distribution at 850 nm
We report on an integrated photonic transmitter of up to 100 MHz repetition
rate, which emits pulses centered at 850 nm with arbitrary amplitude and
polarization. The source is suitable for free space quantum key distribution
applications. The whole transmitter, with the optical and electronic components
integrated, has reduced size and power consumption. In addition, the
optoelectronic components forming the transmitter can be space-qualified,
making it suitable for satellite and future space missions.Comment: 6 figures, 2 table
Quantum control of spin-correlations in ultracold lattice gases
We demonstrate that it is possible to prepare a lattice gas of ultracold
atoms with a desired non-classical spin-correlation function using atom-light
interaction of the kind routinely employed in quantum spin polarization
spectroscopy. Our method is based on quantum non-demolition (QND) measurement
and feedback, and allows in particular to create on demand exponentially or
algebraically decaying correlations, as well as a certain degree of
multi-partite entanglement.Comment: 2 figure
Acoustic characterization of crack damage evolution in sandstone deformed under conventional and true triaxial loading
We thank the Associate Editor, Michelle Cooke, and the reviewers, Ze'ev Reches and Yves Guéguen, for useful comments which helped to improve the manuscript. We thank J.G. Van Munster for providing access to the true triaxial apparatus at KSEPL and for technical support during the experimental program. We thank R. Pricci for assistance with technical drawings of the apparatus. This work was partly funded by NERC award NE/N002938/1 and by a NERC Doctoral Studentship, which we gratefully acknowledge. Supporting data are included in a supporting information file; any additional data may be obtained from J.B. (e-mail: [email protected]).Peer reviewedPublisher PD
- …