Shot Noise of Spin-Decohering Transport in Spin-Orbit Coupled Nanostructures

We generalize the scattering theory of quantum shot noise to include the full spin-density matrix of electrons injected from a spin-filtering or ferromagnetic electrode into a quantum-coherent nanostructure governed by various spin-dependent interactions. This formalism yields the spin-resolved shot noise power for different experimental measurement setups--with ferromagnetic source and ferromagnetic or normal drain electrodes--whose evaluation for the diffusive multichannel quantum wires with the Rashba (SO) spin-orbit coupling shows how spin decoherence and dephasing lead to substantial enhancement of charge current fluctuations (characterized by Fano factors $> 1/3$). However, these processes and the corresponding shot noise increase are suppressed in narrow wires, so that charge transport experiments measuring the Fano factor $F_{\uparrow \to \uparrow \downarrow}$ in a ferromagnet/SO-coupled-wire/paramagnet setup also quantify the degree of phase-coherence of transported spin--we predict a one-to-one correspondence between the magnitude of the spin polarization vector and $F_{\uparrow \to \uparrow \downarrow}$.Comment: 8 pages, 3 figure; enhanced with 2 new figure

Why the Universe Started from a Low Entropy State

We show that the inclusion of backreaction of massive long wavelengths imposes dynamical constraints on the allowed phase space of initial conditions for inflation, which results in a superselection rule for the initial conditions. Only high energy inflation is stable against collapse due to the gravitational instability of massive perturbations. We present arguments to the effect that the initial conditions problem {\it cannot} be meaningfully addressed by thermostatistics as far as the gravitational degrees of freedom are concerned. Rather, the choice of the initial conditions for the universe in the phase space and the emergence of an arrow of time have to be treated as a dynamic selection.Comment: 12 pages, 2 figs. Final version; agrees with accepted version in Phys. Rev.

Dynamics of Global Entanglement under Decoherence

We investigate the dynamics of global entanglement, the Meyer-Wallach measure, under decoherence, analytically. We study two important class of multi-partite entangled states, the Greenberger-Horne-Zeilinger and the W state. We obtain exact results for various models of system-environment interactions (decoherence). Our results shows distinctly different scaling behavior for these initially entangled states indicating a relative robustness of the W state, consistent with previous studies.Comment: 5 pages and 5 figure

On the precise connection between the GRW master-equation and master-equations for the description of decoherence

We point out that the celebrated GRW master-equation is invariant under translations, reflecting the homogeneity of space, thus providing a particular realization of a general class of translation-covariant Markovian master-equations. Such master-equations are typically used for the description of decoherence due to momentum transfers between system and environment. Building on this analogy we show the exact relationship between the GRW master-equation and decoherence master-equations, further providing a collisional decoherence model formally equivalent to the GRW master-equation. This allows for a direct comparison of order of magnitudes of relevant parameters. This formal analogy should not lead to confusion on the utterly different spirit of the two research fields, in particular it has to be stressed that the decoherence approach does not lead to a solution of the measurement problem. Building on this analogy however the feasibility of the extension of spontaneous localization models in order to avoid the infinite energy growth is discussed. Apart from a particular case considered in the paper, it appears that the amplification mechanism is generally spoiled by such modifications.Comment: 9 pages, latex, no figures, to appear on J. Phys.

Decoherence and entropy of primordial fluctuations II. The entropy budget

We calculate the entropy of adiabatic perturbations associated with a truncation of the hierarchy of Green functions at the first non trivial level, i.e. in a self-consistent Gaussian approximation. We give the equation governing the entropy growth and discuss its phenomenology. It is parameterized by two model-dependent kernels. We then examine two particular inflationary models, one with isocurvature perturbations, the other with corrections due to loops of matter fields. In the first model the entropy grows rapidely, while in the second the state remains pure (at one loop).Comment: 28 page

Topologically decoherence-protected qubits with trapped ions

We show that trapped ions can be used to simulate a highly symmetrical Hamiltonian with eingenstates naturally protected against local sources of decoherence. This Hamiltonian involves long range coupling between particles and provides a more efficient protection than nearest neighbor models discussed in previous works. Our results open the perspective of experimentally realizing in controlled atomic systems, complex entangled states with decoherence times up to nine orders of magnitude longer than isolated quantum systems.Comment: 4 page

Quiz Games as a model for Information Hiding

We present a general computation model inspired in the notion of information hiding in software engineering. This model has the form of a game which we call quiz game. It allows in a uniform way to prove exponential lower bounds for several complexity problems of elimination theory.Comment: 46 pages, to appear in Journal of Complexit

A randomised, double-blind, four-way, crossover trial comparing the 24-h FEV₁ profile for once-daily versus twice-daily treatment with olodaterol, a novel long-acting β₂-agonist, in patients with chronic obstructive pulmonary disease

Background: This randomised, double-blind, four-way, crossover, Phase II study compared the 24-h forced expiratory volume in 1 s (FEV1) profile of alternative dosing frequencies of two total daily doses of olodaterol (5 and 10 mu g) in patients with chronic obstructive pulmonary disease (COPD). Methods: Patients received olodaterol 2 mu g twice daily (BID), 5 mu g BID, 5 mu g once daily (QD) and 10 mu g QD in a randomised sequence over 3-week treatment periods. Co-primary end points were FEV, area under the curve from 0 to 12 h (AUC(0-12)) and area under the curve from 12 to 24 h (AUC(12-24)) responses. Additional lung-function responses, pharmacokinetics and safety were assessed. Results: 47 patients were treated. All olodaterol doses provided significant increases in FEV, versus baseline (p < 0.001) and FEV, time profiles were nearly identical for olodaterol 5 and 10 mu g QD. Olodaterol 5 pg QD demonstrated improved FEV, AUC(0-12) and similar AUC(12-24) versus 2 mu g BID. Olodaterol 5 mu g QD showed slightly increased FEV, AUC(0-12) but lower AUC(12-24) compared to 5 mu g BID. Bronchodilation over 24 h was similar for olodaterol 5 pg QD and BID. All doses were well tolerated. Conclusions: Olodaterol 5 pg QD is efficacious in COPD, with a superior bronchodilatory profile compared to 2 mu g BID, which is close to the same total daily dose, and a similar degree of bronchodilation over 24 h compared with double the daily dose (administered as 10 pg QD or 5 mu g BID)