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Dionisis Stefanatos

  1. Time-Optimal Adiabatic-Like Expansion of Bose-Einstein Condensates.

    Пт, 03/09/2012 - 15:01 — SomNambul
    Authors: Dionisis Stefanatos, Jr-Shin Li
    Subjects: Optimization and Control
    Abstract

    In this paper we study the fast adiabatic-like expansion of a one-dimensional
    Bose-Einstein condensate (BEC) confined in a harmonic potential, using the
    theory of time-optimal control. We find that under reasonable assumptions
    suggested by the experimental setup, the minimum-time expansion occurs when the
    frequency of the potential changes in a bang-bang form between the permitted
    values. We calculate the necessary expansion time and show that it scales
    logarithmically with large values of the expansion factor.

  2. The Role of Singular Control in Frictionless Atom Cooling in a Harmonic Trapping Potential.

    Чт, 03/10/2011 - 16:01 — SomNambul
    Authors: Dionisis Stefanatos, Jr-Shin Li
    Subjects: Optimization and Control
    Abstract

    In this article we study the frictionless cooling of atoms trapped in a
    harmonic potential, while minimizing the transient energy of the system. We
    show that in the case of unbounded control, this goal is achieved by a singular
    control, which is also the time-minimal solution for a "dual" problem, where
    the energy is held fixed. In addition, we examine briefly how the solution is
    modified when there are bounds on the control.

  3. Constrained Minimum-Energy Optimal Control of the Dissipative Bloch Equations.

    Втр, 01/26/2010 - 16:01 — SomNambul
    Authors: Dionisis Stefanatos, Jr-Shin Li
    Subjects: Optimization and Control
    Abstract

    In this letter, we apply optimal control theory to design minimum-energy
    $\pi/2$ and $\pi$ pulses for the Bloch system in the presence of relaxation
    with constrained control amplitude. We consider a commonly encountered case in
    which the transverse relaxation rate is much larger than the longitudinal one
    so that the latter can be neglected. Using the Pontryagin's Maximum Principle,
    we derive optimal feedback laws which are characterized by the number of
    switches, depending on the control bound and the coordinates of the desired
    final state.

  4. Optimal Design of Minimum Energy Pulses for Bloch Equations in the case of Dominant Transverse Relaxation.

    Пнд, 08/24/2009 - 13:10 — SomNambul
    Authors: Dionisis Stefanatos
    Subjects: Optimization and Control
    Abstract

    In this report, we apply Optimal Control Theory to design minimum energy
    $\pi/2$ and $\pi$ pulses for Bloch equations, in the case where transverse
    relaxation rate is much larger than longitudinal so the later can be neglected.
    Using Pontryagin's Maximum Principle, we derive an optimal feedback law and
    subsequently use it to obtain analytical expressions for the energy and
    duration of the optimal pulses.

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