Frequency Bin Entangled Photons

A monochromatic laser pumping a parametric down conversion crystal generates frequency entangled photon pairs. We study this experimentally by addressing such frequency entangled photons at telecommunication wavelengths (around 1550 nm) with fiber optics components such as electro-optic phase modulators and narrow band frequency filters. The theory underlying our approach is developed by introducing the notion of frequency bin entanglement. Our results show that the phase modulators address coherently up to eleven frequency bins, leading to an interference pattern which can violate a Bell inequality adapted to our setup by more than five standard deviations.Comment: 10 pages, 4 figures (extended version

Implementing two-photon interference in the frequency domain with electro-optic phase modulators

Frequency-entangled photons can be readily produced using parametric down-conversion. We have recently shown how such entanglement could be manipulated and measured using electro-optic phase modulators and narrow-band frequency filters, thereby leading to two-photon interference patterns in the frequency domain. Here we introduce new theoretical and experimental developments showing that this method is potentially a competitive platform for the realization of quantum communication protocols in standard telecommunication fibres. We derive a simple theoretical expression for the coincidence probabilities and use it to optimize a Bell inequality. Furthermore, we establish an equivalence between the entangled- photon scheme and a classical interference scheme. Our measurements of two-photon interference in the frequency domain yield raw visibilities in excess of 99%. We use our high quality setup to experimentally validate the theoretical predictions, and in particular we report a violation of the CH74 inequality by more than 18 standard deviations.Comment: 19 pages, 3 figure

Dark soliton states of Bose-Einstein condensates in anisotropic traps

Dark soliton states of Bose-Einstein condensates in harmonic traps are studied both analytically and computationally by the direct solution of the Gross-Pitaevskii equation in three dimensions. The ground and self-consistent excited states are found numerically by relaxation in imaginary time. The energy of a stationary soliton in a harmonic trap is shown to be independent of density and geometry for large numbers of atoms. Large amplitude field modulation at a frequency resonant with the energy of a dark soliton is found to give rise to a state with multiple vortices. The Bogoliubov excitation spectrum of the soliton state contains complex frequencies, which disappear for sufficiently small numbers of atoms or large transverse confinement. The relationship between these complex modes and the snake instability is investigated numerically by propagation in real time.Comment: 11 pages, 8 embedded figures (two in color

Observation of the formation of an optical intensity shock and wave breaking in the nonlinear propagation of pulses in optical fibers

We have observed the formation of an optical intensity shock and the subsequent wave breaking in the nonlinear propagation of 1-psec pulses in an optical fiber. The wave breaking manifests itself as the appearance of oscillations trailing the shock, which are due to the beating of widely separated frequency components which bridge the shock. The experimental results are in good agreement with numerical solutions of the nonlinear Schrodinger equation.Peer reviewedElectrical and Computer Engineerin

Dual-polarization OFDM-OQAMfor communications over optical fibers with coherent detection

In order to improve the spectral efficiency of coherent optical communication systems, it has recently been proposed to make use of the orthogonal frequency-division multiplexing offset quadrature amplitude modulation (OFDM-OQAM). Multiple optical channels spaced in the frequency domain by the symbol rate can be transmitted orthogonally, even if each channel overlaps significantly in frequency with its two adjacent channels. The solutions proposed until now in the literature unfortunately only address a single polarization communication, and therefore do not benefit from the capacity gain reached when two polarizations are used to transmit independent information signals. The aim of the present paper is to propose a receiver architecture that can decouple the two polarizations. We build an equalizer per channel at twice the symbol rate and optimize it based on the minimum mean square error (MMSE) criterion. We demonstrate the efficiency of the resulting system compared to the Nyquist wavelength-division multiplexing (N-WDM) system both in terms of performance and complexity. We also assess the system sensitivity to transmit synchronization errors and show that system can even work under significant synchronization errors. © 2013 Optical Society of America

Dark Soliton Pulses. Generation And Propagation Through Single Mode Fibers At A= 0.6 µm

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Picosecond steps and dark pulses through nonlinear single mode fibers

We experimentally observed transmission of “negative pulses” through a single mode optical fiber in conditions where self-phase modulation, due to self induced variations of silica refractive index, may be balanced by the positive group velocity dispersion (dVg/dδSCOPUS: ar.jinfo:eu-repo/semantics/publishe

Spectral-Interferometric Characterization of Nonlinear-Dispersive Similariton

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