446,594 research outputs found
Indistinguishability of independent single photons
The indistinguishability of independent single photons is presented by
decomposing the single photon pulse into the mixed state of different transform
limited pulses. The entanglement between single photons and outer environment
or other photons induces the distribution of the center frequencies of those
transform limited pulses and makes photons distinguishable. Only the single
photons with the same transform limited form are indistinguishable. In details,
the indistinguishability of single photons from the solid-state quantum emitter
and spontaneous parametric down conversion is examined with two-photon
Hong-Ou-Mandel interferometer. Moreover, experimental methods to enhance the
indistinguishability are discussed, where the usage of spectral filter is
highlighted.Comment: 6 pages, 3 figure
Superluminal Noncommutative Photons
With the help of the Seiberg-Witten map, one can obtain an effective action
of a deformed QED from a noncommutative QED. Starting from the deformed QED, we
investigate the propagation of photons in the background of electromagnetic
field, up to the leading order of the noncommutativity parameter. In our
setting (both the electric and magnetic fields are parallel to the coordinate
axis and the nonvanishing component of the noncommutativity parameter is
), we find that the electric field has no effect on the
propagation of photons, but the velocity of photons can be larger than the
speed of light () when the propagating direction of photons is
perpendicular to the direction of background magnetic field, while the
light-cone condition does not change when the propagating direction is parallel
to the background magnetic field. The causality associated with the
superluminal photons is discussed briefly.Comment: Revtex, 11 pages, v3: corrected an estimation on page 7 of deviation
from the speed of ligh
Tailoring Single and Multiphoton Probabilities of a Single Photon On-Demand Source
As typically implemented, single photon sources cannot be made to produce
single photons with high probability, while simultaneously suppressing the
probability of yielding two or more photons. Because of this, single photon
sources cannot really produce single photons on demand. We describe a
multiplexed system that allows the probabilities of producing one and more
photons to be adjusted independently, enabling a much better approximation of a
source of single photons on demand.Comment: 4 pages, LaTex, 2 figures, twocolumn and RevTex Style for PR
Spatial entanglement of paired photons generated in cold atomic ensembles
Cold atomic ensembles can mediate the generation of entanglement between
pairs of photons. Photons with specific directions of propagation are detected,
and the entanglement can reside in any of the degrees of freedom that describe
the whole quantum state of the photons: polarization, spatial shape or
frequency. We show that the direction of propagation of the generated photons
determines the spatial quantum state of the photons and therefore, the amount
of entanglement generated. When photons generated in different directions are
combined, this spatial distinguishing information can degrade the quantum
purity of the polarization or frequency entanglement.Comment: 5 pages, 4 figures. Submitted to Phys. Rev. A.; one figure (Fig. 3)
was added, typos and labels in figure 2 were correcte
Entanglement of photons
It is argued that the title of this paper represents a misconception.
Contrary to widespread beliefs it is electromagnetic field modes that are
``systems'' and can be entangled, not photons. The amount of entanglement in a
given state is shown to depend on redefinitions of the modes; we calculate the
minimum and maximum over all such redefinitions for several examples.Comment: 5 pages ReVTe
Experimental position-time entanglement with degenerate single photons
We report an experiment in which two-photon interference occurs between
degenerate single photons that never meet. The two photons travel in opposite
directions through our fibre-optic interferometer and interference occurs when
the photons reach two different, spatially separated, 2-by-2 couplers at the
same time. We show that this experiment is analogous to the conventional
Franson-type entanglement experiment where the photons are entangled in
position and time. We measure wavefunction overlaps for the two photons as high
as 94 3%.Comment: Updated to published version, new fig. 4., corrected typo
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