Search results for "mesoscopic"
showing 10 items of 709 documents
Counting atoms using interaction blockade in an optical superlattice.
2008
We report on the observation of an interaction blockade effect for ultracold atoms in optical lattices, analogous to Coulomb blockade observed in mesoscopic solid state systems. When the lattice sites are converted into biased double wells, we detect a discrete set of steps in the well population for increasing bias potentials. These correspond to tunneling resonances where the atom number on each side of the barrier changes one by one. This allows us to count and control the number of atoms within a given well. By evaluating the amplitude of the different plateaus, we can fully determine the number distribution of the atoms in the lattice, which we demonstrate for the case of a superfluid …
Phonon Avalanche and Superradiance in Paramagnetic Relaxation
1979
New quantum equations for superradiance in extended systems are presented. The possibility of acoustic superradiant emission is discussed on the basis of these equations and a new condition is introduced for superradiance to prevail over incoherent phonon avalanche.
Random population model to explain the recombination dynamics in single InAs/GaAs quantum dots under selective optical pumping
2011
18 páginas, 3 tablas, 9 figuras.-- et al.
Zero-point excitation of a circularly moving detector in an atomic condensate and phonon laser dynamical instabilities
2020
We study a circularly moving impurity in an atomic condensate for the realisation of superradiance phenomena in tabletop experiments. The impurity is coupled to the density fluctuations of the condensate and, in a quantum field theory language, it serves as an analog of a detector for the quantum phonon field. For sufficiently large rotation speeds, the zero-point fluctuations of the phonon field induce a sizeable excitation rate of the detector even when the condensate is initially at rest in its ground state. For spatially confined condensates and harmonic detectors, such a superradiant emission of sound waves provides a dynamical instability mechanism leading to a new concept of phonon l…
Decoherence of the Exciton and Decay of the Excitonic Polaron in Quantum Dots
2005
Bulk-phonon mechanisms of decoherence of an exciton confined in a quantum dot (QD) are considered in order to establish time limitations for the coherent control of the exciton with relevance to its application in quantum information processing. These are the formation and decay of the excitonic polaron. The estimations of characteristic dephasing times for the InAs/GaAs QD are discussed.
Dynamics and inertia of skyrmionic spin structures
2015
Understanding the motion of magnetic skyrmions is essential if they are to be used as information carriers in devices. It is now shown that topological confinement endows the skyrmions with an unexpectedly large mass, which plays a key role in their dynamics.
Surface Acoustic Bloch Oscillations, the Wannier-Stark Ladder, and Landau-Zener Tunneling in a Solid
2010
We present the experimental observation of Bloch oscillations, the Wannier-Stark ladder, and Landau-Zener tunneling of surface acoustic waves in perturbed grating structures on a solid substrate. A model providing a quantitative description of our experimental observations, including multiple Landau-Zener transitions of the anticrossed surface acoustic Wannier-Stark states, is developed. The use of a planar geometry for the realization of the Bloch oscillations and Landau-Zener tunneling allows a direct access to the elastic field distribution. The vertical surface displacement has been measured by interferometry.
Dynamics and topological mass of skyrmionic spin structures (presentation video)
2014
Skyrmions are topologically protected particle-like configurations, with a topological complexity described by their Skyrmion number. In magnetic systems, they have been numerically predicted to exhibit rich dynamics, such as the gyrotropic and breathing modes, dominated by their topology. Recent experimental advances brought their static manipulation well under control. However, their dynamical behaviour is largely unexplored experimentally. In this work, we provide with the first direct observation of eigenmode skyrmion dynamics. In particular, we present dynamical imaging data with high temporal and spatial resolution to demonstrate the GHz gyrotropic mode of a single skyrmion bubble, as…
Entanglement control in hybrid optomechanical systems
2012
We demonstrate the control of entanglement in a hybrid optomechanical system comprising an optical cavity with a mechanical end-mirror and an intracavity Bose-Einstein condensate (BEC). Pulsed laser light (tuned within realistic experimental conditions) is shown to induce an almost sixfold increase of the atom-mirror entanglement and to be responsible for interesting dynamics between such mesoscopic systems. In order to assess the advantages offered by the proposed control technique, we compare the time-dependent dynamics of the system under constant pumping with the evolution due to the modulated laser light.
Superconducting single-electron transistor and the phi-modulation of supercurrent
2002
An analytical expression for the supercurrent of a superconducting single-electron transistor (SSET) is derived. The derivation is based on analogy between the model Hamiltonian for E_J>E_C and a discrete, one-dimensional harmonic oscillator (1DDHO). The resulting supercurrent is nearly identical to the supercurrent obtained from a continuous harmonic oscillator Hamiltonian.