40 research outputs found
Statistics of light in Raman and Brillouin nonlinear couplers
Statistical properties of optical fields in nonlinear couplers composed of
two waveguides in which Raman or Brillouin processes (with classical pumping)
are in operation and which are mutually connected through the Stokes and/or
anti-Stokes linear interactions are investigated within the framework of
generalized superposition of coherent fields and quantum noise. Heisenberg
equations describing the couplers are solved both analytically under special
conditions and numerically in general cases. Regimes for nonclassical
properties of optical fields, such as sub-Poissonian photon-number statistics,
negative reduced moments of integrated intensity and squeezing of quadrature
fluctuations are discussed for the cases of single and compound fields. General
results are compared with those from short-length approximation.Comment: LATEX, 20 pages, 19 PostScript figure
Quantum dynamics and statistics of two coupled down-conversion processes
In the framework of Heisenberg-Langevin theory the dynamical and statistical
effects arising from the linear interaction of two nondegenerate
down-conversion processes are investigated. Using the strong-pumping
approximation the analytical solution of equations of motion is calculated. The
phenomena reminiscent of Zeno and anti-Zeno effects are examined. The
possibility of phase-controlled and mismatch-controlled switching is
illustrated.Comment: 17 pages, 7 figure
Generation of squeezed light in a nonlinear asymmetric directional coupler
We show that a nonlinear asymmetric directional coupler composed of a linear
waveguide and a nonlinear waveguide operating by nondegenerate parametric
amplification is an effective source of single-mode squeezed light. This is has
been demonstrated, under certain conditions and for specific modes, for
incident coherent beams in terms of the quasiprobability functions,
photon-number distribution and phase distribution.Comment: 19 pages, 5 figure
Quantum and Classical Noise in Practical Quantum Cryptography Systems based on polarization-entangled photons
Quantum-cryptography key distribution (QCKD) experiments have been recently
reported using polarization-entangled photons. However, in any practical
realization, quantum systems suffer from either unwanted or induced
interactions with the environment and the quantum measurement system, showing
up as quantum and, ultimately, statistical noise. In this paper, we investigate
how ideal polarization entanglement in spontaneous parametric downconversion
(SPDC) suffers quantum noise in its practical implementation as a secure
quantum system, yielding errors in the transmitted bit sequence. Because all
SPDC-based QCKD schemes rely on the measurement of coincidence to assert the
bit transmission between the two parties, we bundle up the overall quantum and
statistical noise in an exhaustive model to calculate the accidental
coincidences. This model predicts the quantum-bit error rate and the sifted key
and allows comparisons between different security criteria of the hitherto
proposed QCKD protocols, resulting in an objective assessment of performances
and advantages of different systems.Comment: Rev Tex Style, 2 columns, 7 figures, (a modified version will appear
on PRA
On the evolution of superposition of squeezed displaced number states with the multiphoton Jaynes-Cummings model
In this paper we discuss the quantum properties for superposition of squeezed
displaced number states against multiphoton Jaynes-Cummings model (JCM). In
particular, we investigate atomic inversion, photon-number distribution,
purity, quadrature squeezing, Mandel parameter and Wigner function. We show
that the quadrature squeezing for three-photon absorption case can exhibit
revivals and collapses typical to those occurring in the atomic inversion for
one-photon absorption case. Also we prove that for odd number absorption
parameter there is a connection between the evolution of the atomic inversion
and the evolution of the Wigner function at the origin in phase space.
Furthermore, we show that the nonclassical states whose the Wigner functions
values at the origins are negative will be always nonclassical when they are
evolving through the JCM with even absorption parameter. Also we demonstrate
that various types of cat states can be generated via this system.Comment: 27 pages, 10 figure
Quantum Interferometric Optical Lithography: Exploiting Entanglement to Beat The Diffraction Limit
Classical, interferometric, optical lithography is diffraction limited to
writing features of a size lambda/2 or greater, where lambda is the optical
wavelength. Using nonclassical photon number states, entangled N at a time, we
show that it is possible to write features of minimum size lambda/(2N) in an
N-photon absorbing substrate. This result surpasses the usual classical
diffraction limit by a factor of N. Since the number of features that can be
etched on a two-dimensional surface scales inversely as the square of the
feature size, this allows one to write a factor of N^2 more elements on a
semiconductor chip. A factor of N = 2 can be achieved easily with entangled
photon pairs generated from optical parametric downconversion. It is shown how
to write arbitrary 2D patterns by using this method.Comment: 9 pages, 2 figure