Search results for "Rash"
showing 10 items of 377 documents
Ultrafast Fault-Tolerant Long-Distance Quantum Communication with Static Linear Optics
2017
We present an in-depth analysis regarding the error resistance and optimization of our all-optical Bell measurement and ultrafast long-distance quantum communication scheme proposed in [arXiv:1503.06777]. In order to promote our previous proposal from loss- to fault-tolerance, we introduce a general and compact formalism that can also be applied to other related schemes (including non-all-optical ones such as [PRL 112, 250501]). With the help of this new representation we show that our communication protocol does not only counteract the inevitable photon loss during channel transmission, but is also able to resist common experimental errors such as Pauli-type errors (bit- and phase-flips) a…
Visualizing a protein quake with time-resolved X-ray scattering at a free-electron laser
2014
We describe a method to measure ultrafast protein structural changes using time-resolved wide-angle X-ray scattering at an X-ray free-electron laser. We demonstrated this approach using multiphoton excitation of the Blastochloris viridis photosynthetic reaction center, observing an ultrafast global conformational change that arises within picoseconds and precedes the propagation of heat through the protein. This provides direct structural evidence for a 'protein quake': the hypothesis that proteins rapidly dissipate energy through quake-like structural motions. peerReviewed
Ultrafast dynamics of indirect exchange interaction and transient spin current generation in a two-dimensional electron gas
2017
We predict that a driven localized magnetic moment coupled to mobile carriers of a metal or semiconductor surface or interface generates a specific dynamics of the carrier spin density as well as a transient spin current. Numerical results illustrate the time-dependent Friedel oscillations and the associated ultrafast Ruderman-Kittel- Kasuya-Yosida (RKKY) interaction as well as the spin current generated by the impurity spin flipping. Retardation effects of the indirect exchange interaction of the impurity spins via the conduction electrons are found and discussed. Our results point to an alternative way of controlling the local magnetization on a subpicosecond time scale via appropriate tu…
Real-Time Measurements of Ultrafast Instabilities in Nonlinear Fiber Optics: Recent Advances
2019
Recent years have seen renewed interest in the study of nonlinear fibre laser and propagation dynamics through the use of real-time measurement techniques for non-repetitive ultrafast optical signals. In this paper we review our recent work in this field using dispersive Fourier Transform and Time Lens techniques.
Relativistic Neel-order fields induced by electrical current in antiferromagnets
2014
We predict that a lateral electrical current in antiferromagnets can induce non-equilibrium N\'eel order fields, i.e. fields whose sign alternates between the spin sublattices, which can trigger ultra-fast spin-axis reorientation. Based on microscopic transport theory calculations we identify staggered current-induced fields analogous to the intra-band and to the intrinsic inter-band spin-orbit fields previously reported in ferromagnets with a broken inversion-symmetry crystal. To illustrate their rich physics and utility, we considered bulk Mn2Au with the two spin sublattices forming inversion partners, and a 2D square-lattice antiferromagnet with broken structural inversion symmetry model…
Ultrafast non-linear optical signal from a single quantum dot: exciton and biexciton effects
2002
We present results on both the intensity and phase-dynamics of the transient non-linear optical response of a single quantum dot (SQD). The time evolution of the Four Wave Mixing (FWM) signal on a subpicosecond time scale is dominated by biexciton effects. In particular, for the cross-polarized excitation case a biexciton bound state is found. In this latter case, mean-field results are shown to give a poor description of the non-linear optical signal at small times. By properly treating exciton-exciton effects in a SQD, coherent oscillations in the FWM signal are clearly demonstrated. These oscillations, with a period corresponding to the inverse of the biexciton binding energy, are correl…
Dynamics of distorted and undistorted soliton molecules in a mode-locked fiber laser
2019
Recent developments in real-time ultrafast measurement techniques have enabled us to prove experimentally that soliton molecules execute internal motions with some aspects similar to those of a matter molecule. Such an analogy between the dynamics of soliton molecules and the dynamics of matter molecules is based on the assumption that the dissipative solitons constituting a molecule are rigid entities sharing a common profile. Whereas this assumption drastically reduces the number of degrees of freedom, it does not hold true in general and we demonstrate that it overlooks some of the essential dynamical features of the soliton molecule. We present a theoretical study based on the principle…
Ultrafast beam shaping with high-numerical-aperture microscope objectives
2009
Ultrafast diffraction results in spatiotemporal un-coupling of the wave field, inducing spectral anomalies and pulse stretching. Localized compensation may be achieved via angular dispersion driven by diffractive optical elements (DOEs). We report on an DOEs-based beam shaper of ultrashort optical pulses with high spatiotemporal resolution. Inspection of the validity of our approach is performed in the single-cycle regime.
Nonlinear pulse shaping and polarization dynamics in mode-locked fiber lasers
2014
International audience; We review our recent progress on the study of new nonlinear mechanisms of pulse shaping in passively mode-locked fiber lasers. These include a mode-locking regime featuring pulses with a triangular distribution of the intensity, and spectral compression arising from nonlinear pulse propagation. We also report on our recent experimental studies unveiling new types of vector solitons with processing states of polarization for multi-pulse and tightly bound-state soliton (soliton molecule) operations in a carbon nanotube (CNT) mode-locked fiber laser with anomalous dispersion cavity.
Self-similarity in ultrafast nonlinear optics
2007
International audience; Recent developments in nonlinear optics have led to the discovery of a new class of ultrashort pulse, the `optical similariton'. Optical similaritons arise when the interaction of nonlinearity, dispersion and gain in a high-power fibre amplifier causes the shape of an arbitrary input pulse to converge asymptotically to a pulse whose shape is self-similar. In comparison with optical solitons, which rely on a delicate balance of nonlinearity and anomalous dispersion and which can become unstable with increasing intensity, similaritons are more robust at high pulse powers. The simplicity and widespread availability of the components needed to build a self-similar amplif…