1,721,315 research outputs found
Letter from Viola L. Hart, December 5, 1967
No full textLetter from Viola L. Hart to Fayez Sayegh, December 5, 1967, regarding his appearance on the David Susskind show and the Arab-Israeli conflict
Il velo islamico davanti ai giudici italiani (ed europei) [The hijab before Italian (and European) judges]
No full textMarriage record of Maddan, J. H. and Black, Viola L.
No full textMarriage license for J.H. Maddan and Viola L. Black. R. Bowen Daniel was the officiant
The marriage record of Munins, Joshua and Burk, Viola L
No full textMarriage license for Joshua Munins and Viola L. Burk. G.W. Hawkins was the officiant
Quantum Markovian Subsystems: Invariance, Attractivity, and Control
No full textWe characterize the dynamical behavior of continuous-time, Markovian quantum systems with respect to a subsystem of interest. Markovian dynamics describes a wide class of open quantum systems of relevance to quantum information processing, subsystem encodings offering a general pathway to faithfully represent quantum information. We provide explicit linear-algebraic characterizations of the notion of invariant and noiseless subsystem for Markovian master equations, under different robustness assumptions for model-parameter and initial-state variations. The stronger concept of an attractive quantum subsystem is introduced, and sufficient existence conditions are identified based on Lyapunov's stability techniques. As a main control application, we address the potential of output-feedback Markovian control strategies for quantum pure state-stabilization and noiseless-subspace generation. In particular, explicit results for the synthesis of stabilizing semigroups and noiseless subspaces in finite-dimensional Markovian systems are obtained
Quantum damping of position due to energy measurements
No full textThe quantum theory for measurements of energy is introduced and its consequences for the average position of monitored dynamical systems are analyzed. It turns out that energy measurements lead to a localization of the expectation values of other observables. This is manifested, in the case of position, as a damping of the motion without classical analog. Quantum damping of position for an atom bouncing on a reflecting surface in the presence of a homogeneous gravitational field is dealt with in detail and the connection with an experiment already performed in the classical regime is studied. We show that quantum damping is testable provided that the same measurement strength obtained in the experimental verification of the quantum Zeno effect in atomic spectroscopy [W. M. Itano et al., Phys. Rev. A 41, 2295 (1990)] is made available
Gravitation at the mesoscopic scale
No full textFree fall experiments are discussed by using test masses associated to quantum states not necessarily possessing a classical counterpart. The times of flight of the Galilean experiments using classical test masses are replaced in the quantum case by probability distributions which, although still not defined in an uncontroversial manner, become manifestly dependent upon the mass and the initial state. Such a dependence is also expected in non-inertial frames of reference if the weak equivalence principle still holds. The latter could be tested, merging recent achievements in mesoscopic physics, by using cooled atoms in free fall and accelerated frames initially prepared in nonclassical quantum states
Attractive quantum subsystem and feedback-stabilization problems.
No full textWe propose a general theoretical framework that is suitable to study a wide class of stabilization problems for quantum Markovian dynamical systems. Building on system-theoretic ideas, we propose definitions of invariant and attractive quantum subsystem, characterize Markovian invariance properties, and provide sufficient conditions for
attraction. The general framework and results are illustrated by addressing the potential of output-feedback Markovian control strategies for quantum pure state-stabilization. In particular,
constructive results for the synthesis of stabilizing semigroups in arbitrary finite-dimensional Markovian systems are established
Dynamics of decoherence in continuous atom-optical quantum nondemolition measurements
No full textThe Lindblad approach to continuous quantum measurements is applied to a system composed of a two-level atom interacting with a stationary quantized electromagnetic held through a dispersive coupling, fulfilling quantum nondemolition criteria. Two schemes of measurements are examined. The first one consists of measuring the atomic electric dipole, which indirectly allows one to infer the photon distribution inside the cavity. The second one schematizes a measurement of photon momentum, which permits one to describe the atomic level distribution; Decoherence of the corresponding reduced density matrices is studied in detail for both cases, and its relationship to recent experiments is finally discussed
Analysis and synthesis of attractive quantum Markovian dynamics
No full textWe propose a general framework for investigating a large class of stabilization problems in Markovian quantum systems. Building on the notions of invariant and attractive quantum subsystem, we characterize attractive subspaces by exploring the structure of the invariant sets for the dynamics. Our general analysis results are exploited to assess the ability of open-loop Hamiltonian and output-feedback control strategies to synthesize Markovian generators which stabilize a target subsystem, subspace, or pure state. In particular, we provide an algebraic characterization of the manifold of stabilizable pure states in arbitrary finite-dimensional Markovian systems, that leads to a constructive strategy for designing the relevant controllers. Implications for stabilization of entangled pure states are addressed by example
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