Amplitude-squeezed pulsed light has been produced using a<br> microstructured silica fibre. By spectrally filtering after the<br> non-linear propagation in the fibre a squeezing value of -1.7 dB has<br> been measured. A quantum key distribution scheme based on squeezed light<br> from such microstructured fibres is proposed.
Time evolution of a quantum soliton in a Kerr medium
N Korolkova,
R Loudon,
G Gardavsky,
MW Hamilton,
Gerd Leuchs
JOURNAL OF MODERN OPTICS
48
(8)
1339-1355
(2001)
| Journal
The Q-function of the quantum soliton in a fibre is derived in a new<br> form suitable for the assessment of the possibilities for experimental<br> observations of specific quantum-soliton effects. The characteristic<br> effects of soliton evolution are associated with a cubic term in the<br> nonlinear phase angle and appear at distances well beyond the<br> attenuation length (long range). At the accessible distances, the<br> nonlinear dynamics of a fundamental soliton follows essentially the<br> single-mode dynamics (short and middle range). However, for the<br> higher-order solitons, the form of the evolution parameter suggests<br> strong deviations of soliton dynamics from the single-mode with a square<br> of soliton number. The use of enhanced-nonlinearity fibres and<br> higher-order solitons might make the experimental studies of the<br> specific quantum-soliton features more viable.
Generation of continuous variable Einstein-Podolsky-Rosen entanglement
via the Kerr nonlinearity in an optical fiber
Christine Silberhorn,
PK Lam,
O Weiss,
F Konig,
N Korolkova,
Gerd Leuchs
We report on the generation of a continuous variable<br> Einstein-Podolsky-Rosen (EPR) entanglement using an optical fiber<br> interferometer. The Kerr nonlinearity in the fiber is exploited for the<br> generation of two independent squeezed beams. These interfere at a beam<br> splitter and EPR entanglement is obtained between the output beams. The<br> correlation of the amplitude (phase) quadratures is measured to be 4.0<br> +/- 0.2 (4.0 +/- 0.4) dB below the quantum noise limit. The sum<br> criterion for these squeezing variances 0.80 +/- 0.03 < 2 verifies the<br> nonseparability of the state. The product of the inferred uncertainties<br> for one beam (0.64 +/- 0.08) is well below the EPR limit of unity.
The role of coherent effects in mode bistability of a gas laser in inhomogeneous medium
G Wasik,
Gerd Leuchs
JOURNAL OF MODERN OPTICS
48
(4)
671-684
(2001)
| Journal
We have studied microscopic effects leading to mode competition in an<br> inhomogeneously broadened medium of a gas laser with a weakly<br> anisotropic cavity. The polarization bistability observed in some<br> lasers, which is believed to be caused by hole burning, we attribute to<br> microscopic coherent effects induced by two light fields. Due to these<br> effects one field can be coupled with another. Hole burning is found to<br> be important, but not crucial. The exact solution of the equation of<br> motion for field amplitudes is compared with the third order<br> approximation of perturbation theory. The role of four wave mixing,<br> important for bistability of axial modes in a homogeneously broadened<br> medium, is discussed.
The focus of light - theoretical calculation and experimental tomographic reconstruction
Susanne Quabis,
Ralf Dorn,
M. Eberler,
O. Glöckl,
Gerd Leuchs
We present numerical calculations on the field distribution in the focus of an optical system with high numerical aperture. The diffraction integrals which are based on the Debye approximation are derived and evaluated for a radially polarized input field with a doughnut-shaped intensity distribution. It is shown that this mode focusses down to a spot size significantly smaller as compared to the case of linear polarization. An experimental setup to measure the three-dimensional intensity distribution in the focal region is presented, which is based on the knife-edge method and on tomographic reconstruction.
Bright EPR-entangled beams for quantum communication
Christine Silberhorn,
PK Lam,
N Korolkova,
Gerd Leuchs
QUANTUM COMMUNICATION, COMPUTING, AND MEASUREMENT 3
443-447
(2001)
Bright Einstein-Podolsky-Rosen (EPR) entanglement is obtained in linear<br> interference of two amplitude-squeezed beams produced in Kerr nonlinear<br> interactions. The correlation of the amplitude (phase) quadratures are<br> measured to be 4.0 +/- 0.2(4.0 +/- 0.4) dB below the quantum noise<br> limit. Continuous variable EPR-paradox was demonstrated with measured<br> product of the conditional variances of 0.64 +/- 0.08, well below the<br> quantum limit of unity.
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