Angular Schmidt Modes in Spontaneous Parametric Down-Conversion

We report a proof-of-principle experiment demonstrating that appropriately chosen set of Hermite-Gaussian modes constitutes a Schmidt decomposition for transverse momentum states of biphotons generated in the process of spontaneous parametric down conversion. We experimentally realize projective measurements in Schmidt basis and observe correlations between appropriate pairs of modes. We perform tomographical state reconstruction in the Schmidt basis, by direct measurement of single-photon density matrix eigenvalues.Comment: 5 pages, 4 figure

Azimuthal distinguishability of entangled photons generated in spontaneous parametric down-conversion

We experimentally demonstrate that paired photons generated in different sections of a down-conversion cone, when some of the interacting waves show Poynting vector walk-off, carry different spatial correlations, and therefore a different degree of spatial entanglement. This is shown to be in agreement with theoretical results. We also discuss how this azimuthal distinguishing information of the down-conversion cone is relevant for the implementation of quantum sources aimed at the generation of entanglement in other degrees of freedom, such as polarization.Comment: 7 pages, 5 figures, submitted to Opt. Expres

Direct detection of a single photon by humans

Despite investigations for over 70 years, the absolute limits of human vision have remained unclear. Rod cells respond to individual photons, yet whether a single-photon incident on the eye can be perceived by a human subject has remained a fundamental open question. Here we report that humans can detect a single-photon incident on the cornea with a probability significantly above chance. This was achieved by implementing a combination of a psychophysics procedure with a quantum light source that can generate single-photon states of light. We further discover that the probability of reporting a single photon is modulated by the presence of an earlier photon, suggesting a priming process that temporarily enhances the effective gain of the visual system on the timescale of seconds

Probing quantum coherence in qubit arrays

We discuss how the observation of population localization effects in periodically driven systems can be used to quantify the presence of quantum coherence in interacting qubit arrays. Essential for our proposal is the fact that these localization effects persist beyond tight-binding Hamiltonian models. This result is of special practical relevance in those situations where direct system probing using tomographic schemes becomes infeasible beyond a very small number of qubits. As a proof of principle, we study analytically a Hamiltonian system consisting of a chain of superconducting flux qubits under the effect of a periodic driving. We provide extensive numerical support of our results in the simple case of a two-qubits chain. For this system we also study the robustness of the scheme against different types of noise and disorder. We show that localization effects underpinned by quantum coherent interactions should be observable within realistic parameter regimes in chains with a larger number o

Brand clarity of local and global brands in fast-moving consumer goods : an empirical study in a Middle East country

Purpose - This paper aims to analyze different brand clarity levels (BCLs) of local, global and glocal types of brands in fast-moving consumer goods from the consumer's perspective. The study also intends to identify whether the consumer's previous experience with such brands may impact BCL. Design/methodology/approach - Twenty-eight global and local brands were used to test the hypotheses by conducting a survey with 400 consumers in the emerging economy of Iran. The authors applied a quantitative technique of brand classification, previously proposed in the literature. After categorizing the brands as local, global or glocal, one-way ANOVA, Tukey post hoc and t-test analyses were performed to identify whether the different types of brands had different BCLs. Findings - The results showed that brand clarity was significantly higher for local bands than for global or glocal brands and that it was higher for glocal bands than for global brands. Furthermore, the consumer's prior experience with a brand had no impact on BCL for different types of brands. Social implications - For global brand managers, it is essential to know that local brands in Middle Eastern emerging markets may have more brand clarity than global brands. Therefore, if global brands intend to enter these markets, adopting a glocal positioning appears to be a helpful strategy. Besides, the results suggest that managers should analyze brand categorization from the consumer's perspective, i.e. from a subjective instead of an objective perspective. Originality/value - This was the first study analyzing the BCL of local, global and glocal brands and identifying significant differences in their BCL

Brand clarity of local and global brands in fast-moving consumer goods : an empirical study in a Middle East country

Purpose - This paper aims to analyze different brand clarity levels (BCLs) of local, global and glocal types of brands in fast-moving consumer goods from the consumer's perspective. The study also intends to identify whether the consumer's previous experience with such brands may impact BCL. Design/methodology/approach - Twenty-eight global and local brands were used to test the hypotheses by conducting a survey with 400 consumers in the emerging economy of Iran. The authors applied a quantitative technique of brand classification, previously proposed in the literature. After categorizing the brands as local, global or glocal, one-way ANOVA, Tukey post hoc and t-test analyses were performed to identify whether the different types of brands had different BCLs. Findings - The results showed that brand clarity was significantly higher for local bands than for global or glocal brands and that it was higher for glocal bands than for global brands. Furthermore, the consumer's prior experience with a brand had no impact on BCL for different types of brands. Social implications - For global brand managers, it is essential to know that local brands in Middle Eastern emerging markets may have more brand clarity than global brands. Therefore, if global brands intend to enter these markets, adopting a glocal positioning appears to be a helpful strategy. Besides, the results suggest that managers should analyze brand categorization from the consumer's perspective, i.e. from a subjective instead of an objective perspective. Originality/value - This was the first study analyzing the BCL of local, global and glocal brands and identifying significant differences in their BCL

Can quantum fractal fluctuations be observed in an atom-optics kicked rotor experiment?

We investigate the parametric fluctuations in the quantum survival probability of an open version of the delta-kicked rotor model in the deep quantum regime. Spectral arguments [Guarneri I and Terraneo M 2001 Phys. Rev. E vol. 65 015203(R)] predict the existence of parametric fractal fluctuations owing to the strong dynamical localisation of the eigenstates of the kicked rotor. We discuss the possibility of observing such dynamically-induced fractality in the quantum survival probability as a function of the kicking period for the atom-optics realisation of the kicked rotor. The influence of the atoms' initial momentum distribution is studied as well as the dependence of the expected fractal dimension on finite-size effects of the experiment, such as finite detection windows and short measurement times. Our results show that clear signatures of fractality could be observed in experiments with cold atoms subjected to periodically flashed optical lattices, which offer an excellent control on interaction times and the initial atomic ensemble.Comment: 18 pp, 7 figs., 1 tabl