718 research outputs found
Ultra-broadband photon pair preparation by spontaneous four wave mixing in dispersion-engineered optical fiber
We present a study of the spectral properties of photon pairs generated
through the process of spontaneous four wave mixing (SFWM) in single mode
fiber. Our analysis assumes narrowband pumps, which are allowed to be
frequency-degenerate or non-degenerate. Based on this analysis, we derive
conditions on the pump frequencies and on the fiber dispersion parameters which
guarantee the generation of ultra-broadband photon pairs. Such photon pairs are
characterized by: i) a very large degree of entanglement, and ii) a very high
degree of temporal synchronization between the signal and idler photons.
Through a numerical exercise, we find that the use of photonic crystal fiber
(PCF) facilitates the fulfilment of the conditions for ultra-broadband photon
pair generation; in particular, the spectral region in which emission occurs
can be adjusted to particular needs through an appropriate choice of the PCF
parameters. In addition, we present a novel quantum interference effect,
resulting from indistinguishable pathways to the same outcome, which can occur
when pumping a SFWM source with multiple spectral lines.Comment: 15 pages, 10 figures. To be published in Phys. Rev.
Orientifolds, Branes, and Duality of 4D Gauge Theories
Recently, a D-brane construction in type IIA string theory was shown to yield
the electric/magnetic duality of four dimensional N=1 supersymmetric U(N_c)
gauge theories with N_f flavours of quark. We present here an extension of that
construction which yields the electric/magnetic duality for the SO(N_c) and
USp(N_c) gauge theories with N_f quarks, by adding an orientifold plane which
is consistent with the supersymmetry. Due to the intersection of the
orientifold plane with the NS-NS fivebranes already present, new features arise
which are crucial in determining the correct final structure of the dualities.Comment: 24 pages, harvmac.tex (b), 6 figures, epsf.tex (Major improvements to
figures; minor improvements to text.
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