Dynamics of entanglement creation between two spins coupled to a chain

We study the dynamics of entanglement between two spins which is created by the coupling to a common thermal reservoir. The reservoir is a spin-$\frac{1}{2}$ Ising transverse field chain thermally excited, the two defect spins couple to two spins of the chain which can be at a macroscopic distance. In the weak-coupling and low-temperature limit the spin chain is mapped onto a bath of linearly interacting oscillators using the Holstein-Primakoff transformation. We analyse the time evolution of the density matrix of the two defect spins for transient times and deduce the entanglement which is generated by the common reservoir. We discuss several scenarios for different initial states of the two spins and for varying distances.Comment: 16 pages, 5 figure

Late Quaternary co-seismic sedimentation in the Sea of Marmara's deep basins

25 pages, 15 figures, 1 tableauInternational audienceThe deep, northern, part of the Sea of Marmara (northwestern Turkey) is composed of several aligned, actively subsiding, basins, which are the direct structural and morphological expression of the North Anatolian Fault's northern branch. The last 20 kyr of their sedimentary fill (lacustrine before 12 kyr BP) have been investigated through giant piston coring onboard R/V MARION-DUFRESNE (MARMACORE Cruise, 2001) and chirp subbottom profiler onboard R/V ATALANTE during MARMARASCARPS Cruise (2002). Especially during the lacustrine stage, the infilling of the deep basins (Tekirda?, Central, Kumburgaz, and Çinarcic Basins; up to 1250 m depth) was dominated by turbidites (with coarse mixed siliciclastic and bioclastic basal part), intercalated in “hemipelagic-type” finegrained calcareous and slightly siliceous clays. Often – especially in the thickest ones – the turbidites show strong segregation and a sharp boundary between coarse part and suspendedload part. In the Central Basin, 8 m of a unique sedimentary event include a 5 to 8m-thick “homogenite” well imaged on seismic profiles. The latter is interpreted as related to a major – possibly triggered - tsunami effect, as described in the Eastern Mediterranean by Kastens and Cita (1981). In the marine (Holocene) upper part of the sedimentary fill, repeated to-and-from structures, affecting silt or fine sand, are evidencing seiche-like effects and, thus, earthquake triggering. Detailed correlations between two deep coring sites (1250 and 1200 m) indicate more than 100 % overthickening in the deepest one; this implies specific processes of distribution of terrigenous input by dense hyperpycnal currents (high kinetic energy, seiche effect, complex reflections on steep slopes). The peculiar sedimentary infilling of the Sea of Marmara's Central Basin (and, by extrapolation, of the whole set) is tentatively interpreted as a direct consequence of the strong seismic activity; the imprint of the latter is more obvious prior to the base of the Holocene, as environmental conditions favoured marginal accumulation (especially on the southern shelf) of large amounts of erosion products available for mass wasting

Intrication et dynamique de trempe dans les chaînes de spins quantiques

The study carried in this thesis concerns the dynamics of out-of-equilibrium quantum systems, and more particularly their entanglement properties. Indeed, entanglement became a fundamental concept in modern physics, especially with the development of quantum information. We have in a first part studied the dynamics of a model of bosons on a lattice after the quench of their trapping potential. In the hard-core limit, we developed an hydrodynamical theory which perfectly reproduced the observed behavior. Then, we have looked at the dynamics of two defect spins coupled to an Ising chain. When these defects have been prepared into a separable state, we have established a formula giving the evolution of the reduced density matrix, allowing us to have access to the entanglement create through the coupling to the chain. We considered then the case of two initially entangled defect spins, and we studied the influence of a non-equilibrium environment on the disentanglement properties. Finally, the last part of this thesis is devoted to the study of a system coupled to an environment by means of the repeated interactions process. We studied the relaxation of the system in two different time regimes. For short times, the state is well described by a non-equilibrium-steady-state, in which we highlighted the scaling properties of some observables. For long times, the system reaches an equilibrium steady state made of a product of Bell statesL'étude menée dans cette thèse concerne la dynamique de systèmes quantiques hors de l'équilibre, et plus particulièrement leurs propriétés d'intrication. En effet, l'intrication est devenue un concept fondamental dans la physique moderne, grâce notamment au développement de l'information quantique. Nous avons dans un premier temps étudié la dynamique d'un modèle de bosons sur réseau après la trempe de leur potentiel de confinement. Dans la limite de coeur dur, nous avons développé une théorie hydrodynamique qui reproduit parfaitement les différents comportements observés. Nous nous sommes ensuite intéressés à la dynamique de deux spins défauts couplés à une chaîne d'Ising. Dans un premier temps, ces défauts ont été préparés dans un état séparable. Nous avons dans ce cas établi une formule donnant l'évolution temporelle de la matrice de densité réduite, qui nous a permis d'avoir accès à l'intrication créée par l'intermédiaire du couplage à la chaîne. Puis, nous avons considéré le cas de deux spins défauts initialement intriqués, et nous avons étudié l'influence d'un environnement hors de l'équilibre sur leurs propriétés de désintrication. Finalement, la dernière partie de cette thèse est consacrée à l'étude d'un système couplé à un environnement décrit par le processus d'interactions répétées. Nous avons étudié la relaxation du système dans deux régimes temporels différents. Pour des temps courts, l'état est bien décrit par un état stationnaire hors équilibre, dans lequel nous avons mis en évidence les propriétés d’échelle de certaines observables. Enfin, pour des temps longs, le système atteint un état stationnaire d'équilibre composé d'un produit d'états de Bel

Entanglement and quench dynamics in quantum spin chains

L'étude menée dans cette thèse concerne la dynamique de systèmes quantiques hors de l'équilibre, et plus particulièrement leurs propriétés d'intrication. En effet, l'intrication est devenue un concept fondamental dans la physique moderne, grâce notamment au développement de l'information quantique. Nous avons dans un premier temps étudié la dynamique d'un modèle de bosons sur réseau après la trempe de leur potentiel de confinement. Dans la limite de coeur dur, nous avons développé une théorie hydrodynamique qui reproduit parfaitement les différents comportements observés. Nous nous sommes ensuite intéressés à la dynamique de deux spins défauts couplés à une chaîne d'Ising. Dans un premier temps, ces défauts ont été préparés dans un état séparable. Nous avons dans ce cas établi une formule donnant l'évolution temporelle de la matrice de densité réduite, qui nous a permis d'avoir accès à l'intrication créée par l'intermédiaire du couplage à la chaîne. Puis, nous avons considéré le cas de deux spins défauts initialement intriqués, et nous avons étudié l'influence d'un environnement hors de l'équilibre sur leurs propriétés de désintrication. Finalement, la dernière partie de cette thèse est consacrée à l'étude d'un système couplé à un environnement décrit par le processus d'interactions répétées. Nous avons étudié la relaxation du système dans deux régimes temporels différents. Pour des temps courts, l'état est bien décrit par un état stationnaire hors équilibre, dans lequel nous avons mis en évidence les propriétés d’échelle de certaines observables. Enfin, pour des temps longs, le système atteint un état stationnaire d'équilibre composé d'un produit d'états de BellThe study carried in this thesis concerns the dynamics of out-Of-Equilibrium quantum systems, and more particularly their entanglement properties. Indeed, entanglement became a fundamental concept in modern physics, especially with the development of quantum information. We have in a first part studied the dynamics of a model of bosons on a lattice after the quench of their trapping potential. In the hard-Core limit, we developed an hydrodynamical theory which perfectly reproduced the observed behavior. Then, we have looked at the dynamics of two defect spins coupled to an Ising chain. When these defects have been prepared into a separable state, we have established a formula giving the evolution of the reduced density matrix, allowing us to have access to the entanglement create through the coupling to the chain. We considered then the case of two initially entangled defect spins, and we studied the influence of a non-Equilibrium environment on the disentanglement properties. Finally, the last part of this thesis is devoted to the study of a system coupled to an environment by means of the repeated interactions process. We studied the relaxation of the system in two different time regimes. For short times, the state is well described by a non-Equilibrium-Steady-State, in which we highlighted the scaling properties of some observables. For long times, the system reaches an equilibrium steady state made of a product of Bell state

Entanglement replication via quantum repeated interactions

We study entanglement creation between two independent XX chains, which are repeatedly coupled locally to spin-1/2 Bell pairs. We show analytically that in the steady state the entanglement of the Bell pairs is perfectly transferred to the chains, generating large-scale interchain pair correlations. However, before the steady state is reached, within a growing causal region around the interacting locus the chains are found in a current driven nonquilibrium steady state (NESS). In the NESS, the chains cross entanglement decays exponentially with respect to the distance to the boundary sites with a typical length scale which is inversely proportional to the driving current

Hydrodynamic description of hard-core bosons on a Galileo ramp

We study the quantum evolution of a cloud of hard-core bosons loaded on a one-dimensional optical lattice after its sudden release from a harmonic trap. Just after the trap has been removed, a linear ramp potential is applied, mimicking the so-called Galileo ramp experiment. The nonequilibrium expansion of the bosonic cloud is elucidated through a hydrodynamical description which is compared to the exact numerical evolution obtained by exact diagonalization on finite lattice sizes. The system is found to exhibit a rich behavior, showing, in particular, Bloch oscillations of a self-trapped condensate and an ejected particle density leading to two diverging entangled condensates. Depending on the initial density of the gas different regimes of Josephson-like oscillations are observed. At low densities, the trapped part of the cloud is in a superfluid phase that oscillates in time as a whole. At higher densities, the trapped condensate is in a mixed superfluid-Mott-insulator phase that show a breathing regime for steep enough potential ramps