9,390 research outputs found
Quantum interference by two temporally distinguishable pulses
We report a two-photon interference effect, in which the entangled photon
pairs are generated from two laser pulses well-separated in time. In a single
pump pulse case, interference effects did not occur in our experimental scheme.
However, by introducing a second pump pulse delayed in time, quantum
interference was then observed. The visibility of the interference fringes
shows dependence on the delay time between two laser pulses. The results are
explained in terms of indistinguishability of biphoton amplitudes which
originated from two temporally separated laser pulses.Comment: two-column, 4pages, submitted to PRA, minor change
A two-dimensional numerical study of the flow inside the combustion chambers of a motored rotary engine
A numerical study was performed to investigate the unsteady, multidimensional flow inside the combustion chambers of an idealized, two-dimensional, rotary engine under motored conditions. The numerical study was based on the time-dependent, two-dimensional, density-weighted, ensemble-averaged conservation equations of mass, species, momentum, and total energy valid for two-component ideal gas mixtures. The ensemble-averaged conservation equations were closed by a K-epsilon model of turbulence. This K-epsilon model of turbulence was modified to account for some of the effects of compressibility, streamline curvature, low-Reynolds number, and preferential stress dissipation. Numerical solutions to the conservation equations were obtained by the highly efficient implicit-factored method of Beam and Warming. The grid system needed to obtain solutions were generated by an algebraic grid generation technique based on transfinite interpolation. Results of the numerical study are presented in graphical form illustrating the flow patterns during intake, compression, gaseous fuel injection, expansion, and exhaust
Two-photon interference with thermal light
The study of entangled states has greatly improved the basic understanding
about two-photon interferometry. Two-photon interference is not the
interference of two photons but the result of superposition among
indistinguishable two-photon amplitudes. The concept of two-photon amplitude,
however, has generally been restricted to the case of entangled photons. In
this letter we report an experimental study that may extend this concept to the
general case of independent photons. The experiment also shows interesting
practical applications regarding the possibility of obtaining high resolution
interference patterns with thermal sources.Comment: Added reference 1
Observation of correlated-photon statistics using a single detector
We report experimental observations of correlated-photon statistics in the
single-photon detection rate. The usual quantum interference in a two-photon
polarization interferometer always accompanies a dip in the single detector
counting rate, regardless of whether a dip or peak is seen in the coincidence
rate. This effect is explained by taking into account all possible photon
number states that reach the detector, rather than considering just the state
post-selected by the coincidence measurement. We also report an
interferometeric scheme in which the interference peak or dip in coincidence
corresponds directly to a peak or dip in the single-photon detection rate.Comment: 4 pages, two-column (minor errors corrected.
GRID2D/3D: A computer program for generating grid systems in complex-shaped two- and three-dimensional spatial domains. Part 2: User's manual and program listing
An efficient computer program, called GRID2D/3D, was developed to generate single and composite grid systems within geometrically complex two- and three-dimensional (2- and 3-D) spatial domains that can deform with time. GRID2D/3D generates single grid systems by using algebraic grid generation methods based on transfinite interpolation in which the distribution of grid points within the spatial domain is controlled by stretching functions. All single grid systems generated by GRID2D/3D can have grid lines that are continuous and differentiable everywhere up to the second-order. Also, grid lines can intersect boundaries of the spatial domain orthogonally. GRID2D/3D generates composite grid systems by patching together two or more single grid systems. The patching can be discontinuous or continuous. For continuous composite grid systems, the grid lines are continuous and differentiable everywhere up to the second-order except at interfaces where different single grid systems meet. At interfaces where different single grid systems meet, the grid lines are only differentiable up to the first-order. For 2-D spatial domains, the boundary curves are described by using either cubic or tension spline interpolation. For 3-D spatial domains, the boundary surfaces are described by using either linear Coon's interpolation, bi-hyperbolic spline interpolation, or a new technique referred to as 3-D bi-directional Hermite interpolation. Since grid systems generated by algebraic methods can have grid lines that overlap one another, GRID2D/3D contains a graphics package for evaluating the grid systems generated. With the graphics package, the user can generate grid systems in an interactive manner with the grid generation part of GRID2D/3D. GRID2D/3D is written in FORTRAN 77 and can be run on any IBM PC, XT, or AT compatible computer. In order to use GRID2D/3D on workstations or mainframe computers, some minor modifications must be made in the graphics part of the program; no modifications are needed in the grid generation part of the program. The theory and method used in GRID2D/3D is described
GRID2D/3D: A computer program for generating grid systems in complex-shaped two- and three-dimensional spatial domains. Part 1: Theory and method
An efficient computer program, called GRID2D/3D was developed to generate single and composite grid systems within geometrically complex two- and three-dimensional (2- and 3-D) spatial domains that can deform with time. GRID2D/3D generates single grid systems by using algebraic grid generation methods based on transfinite interpolation in which the distribution of grid points within the spatial domain is controlled by stretching functions. All single grid systems generated by GRID2D/3D can have grid lines that are continuous and differentiable everywhere up to the second-order. Also, grid lines can intersect boundaries of the spatial domain orthogonally. GRID2D/3D generates composite grid systems by patching together two or more single grid systems. The patching can be discontinuous or continuous. For continuous composite grid systems, the grid lines are continuous and differentiable everywhere up to the second-order except at interfaces where different single grid systems meet. At interfaces where different single grid systems meet, the grid lines are only differentiable up to the first-order. For 2-D spatial domains, the boundary curves are described by using either cubic or tension spline interpolation. For 3-D spatial domains, the boundary surfaces are described by using either linear Coon's interpolation, bi-hyperbolic spline interpolation, or a new technique referred to as 3-D bi-directional Hermite interpolation. Since grid systems generated by algebraic methods can have grid lines that overlap one another, GRID2D/3D contains a graphics package for evaluating the grid systems generated. With the graphics package, the user can generate grid systems in an interactive manner with the grid generation part of GRID2D/3D. GRID2D/3D is written in FORTRAN 77 and can be run on any IBM PC, XT, or AT compatible computer. In order to use GRID2D/3D on workstations or mainframe computers, some minor modifications must be made in the graphics part of the program; no modifications are needed in the grid generation part of the program. This technical memorandum describes the theory and method used in GRID2D/3D
New high-efficiency source of photon pairs for engineering quantum entanglement
We have constructed an efficient source of photon pairs using a
waveguide-type nonlinear device and performed a two-photon interference
experiment with an unbalanced Michelson interferometer. Parametric
down-converted photons from the nonlinear device are detected by two detectors
located at the output ports of the interferometer. Because the interferometer
is constructed with two optical paths of different length, photons from the
shorter path arrive at the detector earlier than those from the longer path. We
find that the difference of arrival time and the time window of the coincidence
counter are important parameters which determine the boundary between the
classical and quantum regime. When the time window of the coincidence counter
is smaller than the arrival time difference, fringes of high visibility
(80 10%) were observed. This result is only explained by quantum theory
and is clear evidence for quantum entanglement of the interferometer's optical
paths.Comment: 4 pages, 4 figures, IQEC200
Comment on ``Dispersion-Independent High-Visibility Quantum Interference ... "
We show in this Comment that the interpretation of experimental data as well
as the theory presented in Atat\"ure et al. [Phys. Rev. Lett. 84, 618 (2000)]
are incorrect and discuss why such a scheme cannot be used to "recover"
high-visibility quantum interference.Comment: Comment on Atat\"ure et al. [Phys. Rev. Lett. 84, 618 (2000)], 2nd
revision, To appear in Phys. Rev. Lett. April, (2001
Dispersion spreading of polarization-entangled states of light and two-photon interference
We study the interference structure of the second-order intensity correlation
function for polarization-entangled two-photon light obtained from type-II
collinear frequency-degenerate spontaneous parametric down-conversion (SPDC).
The structure is visualised due to the spreading of the two-photon amplitude as
two-photon light propagates through optical fibre with group-velocity
dispersion (GVD). Because of the spreading, polarization-entangled Bell states
can be obtained without any birefringence compensation at the output of the
nonlinear crystal; instead, proper time selection of the intensity correlation
function is required. A birefringent material inserted at the output of the
nonlinear crystal (either reducing the initial o-e delay between the oppositely
polarized twin photons or increasing this delay) leads to a more complicated
interference structure of the correlation function.Comment: Extended version of our recent PRL paper. Submitted to PR
Quantum Teleportation with a Complete Bell State Measurement
We report a quantum teleportation experiment in which nonlinear interactions are used for the Bell state measurements. The experimental results demonstrate the working principle of irreversibly teleporting an unknown arbitrary quantum state from one system to another distant system by disassembling into and then later reconstructing from purely classical information and nonclassical EPR correlations. The distinct feature of this experiment is that \emph{all} four Bell states can be distinguished in the Bell state measurement. Teleportation of a quantum state can thus occur with certainty in principle
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