On the Activation of Quantum Nonlocality / Sobre la activación de no-localidad cuántica / Sobre a Ativação da Não-localidade Quântica

Abstract We report on some quantum properties of physical systems, namely, entanglement, nonlocality, k-copy nonlocality (superactivation of nonlocality), hidden nonlocality (activation of nonlocality through local filtering) and the activation of nonlocality through tensoring and local filtering. The aim of this work is two-fold. First, we provide a review of the numerical procedures that must be followed in order to calculate the aforementioned properties, in particular, for any two-qubit system, and reproduce the bounds for two-qudit Werner states. Second, we use such numerical tools to calculate new bounds of these properties for two-qudit Isotropic states and two-qubit Hirsch states.

Resumen Se reportan algunas propiedades cuánticas de sistemas físicos, a saber, entrelazamiento, no-localidad, no-localidad a k-copias (superactivación de la no-localidad), no-localidad oculta (activación de la no-localidad a través de filtrado local) y activación de la no-localidad a través de producto tensorial y filtrado local. Este trabajo tiene dos propósitos: en primer lugar, proporcionar una reseña de los procedimientos numéricos que deben seguirse con el fin de calcular las propiedades mencionadas, en particular para cualquier estado de dos qubits, así como reproducir las cotas para los estados Werner de dos qudits. En segundo lugar, se utilizan estas herramientas numéricas para calcular nuevas cotas de estas propiedades para los estados isotrópicos de dos qudits y los estados de Hirsch de dos qubits.

Resumo Apresentamos um estudo sobre as propriedades quânticas de sistemas físicos, especialmente, o emaranhamento, a não-localidade, a não-localidade k-copy (superativação da não- localidade) e a ativação de não-localidade através do uso de tensores e filtragem local. O objetivo deste trabalho foi duplo. Primeiro, fornecemos uma revisão do procedimento numérico a ser seguido a fim de calcular as propriedades acima mencionadas, em particular, para qualquer sistema de dois- qubits, e que reproduza a ligação para dois-qudit em Estado Werner. Em segundo lugar, utilizamos estas ferramentas numéricas para calcular novas ligações destas propriedades para estados isotrópicos e Hirsch de dois-qudit.

Reconstruction and control of a time-dependent two-electron wave packet.

The concerted motion of two or more bound electrons governs atomic and molecular non-equilibrium processes including chemical reactions, and hence there is much interest in developing a detailed understanding of such electron dynamics in the quantum regime. However, there is no exact solution for the quantum three-body problem, and as a result even the minimal system of two active electrons and a nucleus is analytically intractable. This makes experimental measurements of the dynamics of two bound and correlated electrons, as found in the helium atom, an attractive prospect. However, although the motion of single active electrons and holes has been observed with attosecond time resolution, comparable experiments on two-electron motion have so far remained out of reach. Here we show that a correlated two-electron wave packet can be reconstructed from a 1.2-femtosecond quantum beat among low-lying doubly excited states in helium. The beat appears in attosecond transient-absorption spectra measured with unprecedentedly high spectral resolution and in the presence of an intensity-tunable visible laser field. We tune the coupling between the two low-lying quantum states by adjusting the visible laser intensity, and use the Fano resonance as a phase-sensitive quantum interferometer to achieve coherent control of the two correlated electrons. Given the excellent agreement with large-scale quantum-mechanical calculations for the helium atom, we anticipate that multidimensional spectroscopy experiments of the type we report here will provide benchmark data for testing fundamental few-body quantum dynamics theory in more complex systems. They might also provide a route to the site-specific measurement and control of metastable electronic transition states that are at the heart of fundamental chemical reactions.

Atomic current across an optical lattice.

We devise a microscopic model for the emergence of a collision-induced, fermionic atomic current across a tilted optical lattice. Tuning the--experimentally controllable--parameters of the microscopic dynamics allows us to switch from Ohmic to negative differential conductance.

Ericson fluctuations in an open deterministic quantum system: theory meets experiment.

We provide numerically exact photoexcitation cross sections of rubidium Rydberg states in crossed, static electric, and magnetic fields, in quantitative agreement with recent experimental results. Their spectral backbone underpins a clear transition towards the Ericson regime, associated with a universal, fluctuating behavior of the cross section of strongly coupled, fragmenting quantum systems.