Hot-electron noise suppression in n-Si via the Hall effect

We investigate how hot-electron fluctuations in n-type Si are affected by the presence of an intense (static) magnetic field in a Hall geometry. By using the Monte Carlo method, we find that the known Hall-effect-induced redistribution of electrons among valleys can suppress electron fluctuations with a simultaneous enhancement of the drift velocity

Non-Markovianity of a quantum emitter in front of a mirror

We consider a quantum emitter ("atom") radiating in a one-dimensional (1D) photonic waveguide in the presence of a single mirror, resulting in a delay differential equation for the atomic amplitude. We carry out a systematic analysis of the non-Markovian (NM) character of the atomic dynamics in terms of refined, recently developed notions of quantum non-Markovianity such as indivisibility and information back-flow. NM effects are quantified as a function of the round-trip time and phase shift associated with the atom-mirror optical path. We find, in particular, that unless an atom-photon bound state is formed a finite time delay is always required in order for NM effects to be exhibited. This identifies a finite threshold in the parameter space, which separates the Markovian and non-Markovian regimes.Comment: 7 pages, 4 figures. Fig. 3 featured in Phys. Rev. A Kaleidoscope Images: July 201

Landauer's principle in multipartite open quantum system dynamics

We investigate the link between information and thermodynamics embodied by Landauer's principle in the open dynamics of a multipartite quantum system. Such irreversible dynamics is described in terms of a collisional model with a finite temperature reservoir. We demonstrate that Landauer's principle holds, for such a configuration, in a form that involves the flow of heat dissipated into the environment and the rate of change of the entropy of the system. Quite remarkably, such a principle for {\it heat and entropy power} can be explicitly linked to the rate of creation of correlations among the elements of the multipartite system and, in turn, the non-Markovian nature of their reduced evolution. Such features are illustrated in two exemplary cases.Comment: 5 pages, 3 figures, RevTeX4-1; Accepted for publication in Phys. Rev. Let

Extraction of Singlet States from Noninteracting High-Dimensional Spins

We present a scheme for the extraction of singlet states of two remote particles of arbitrary quantum spin number. The goal is achieved through post-selection of the state of interaction mediators sent in succession. A small number of iterations is sufficient to make the scheme effective. We propose two suitable experimental setups where the protocol can be implemented.Comment: 4 pages, 2 figure

Non-Markovian dynamics from band edge effects and static disorder

It was recently shown [S. Lorenzo, F. Lombardo, F. Ciccarello and M. Palma, Sci. Rep. 7 (2017) 42729] that the presence of static disorder in a bosonic bath \ue2\u80\u94 whose normal modes thus become all Anderson-localized \ue2\u80\u94 leads to non-Markovianity in the emission of an atom weakly coupled to it (a process which in absence of disorder is fully Markovian). Here, we extend the above analysis beyond the weak-coupling regime for a finite-band bath so as to account for band edge effects. We study the interplay of these with static disorder in the emergence of non-Markovian behavior in terms of a suitable non-Markovianity measure

Entanglement-induced electron coherence in a mesoscopic ring with two magnetic impurities

We investigate the Aharonov-Bohm (AB) interference pattern in the electron transmission through a mesoscopic ring in which two identical non-interacting magnetic impurities are embedded. Adopting a quantum waveguide theory, we derive the exact transmission probability amplitudes and study the influence of maximally entangled states of the impurity spins on the electron transmittivity interference pattern. For suitable electron wave vectors, we show that the amplitude of AB oscillations in the absence of impurities is in fact not reduced within a wide range of the electron-impurity coupling constant when the maximally entangled singlet state is prepared. Such state is thus able to inhibit the usual electron decoherence due to scattering by magnetic impurities. We also show how this maximally entangled state of the impurity spins can be generated via electron scattering.Comment: 8 page

Quantum non-Markovianity induced by Anderson localization

As discovered by P. W. Anderson, excitations do not propagate freely in a disordered lattice, but, due to destructive interference, they localise. As a consequence, when an atom interacts with a disordered lattice, one indeed observes a non-trivial excitation exchange between atom and lattice. Such non-trivial atomic dynamics will in general be characterised also by a non-trivial quantum information backflow, a clear signature of non-Markovian dynamics. To investigate the above scenario, we consider a quantum emitter, or atom, weakly coupled to a uniform coupled-cavity array (CCA). If initially excited, in the absence of disorder, the emitter undergoes a Markovian spontaneous emission by releasing all its excitation into the CCA (initially in its vacuum state). By introducing static disorder in the CCA the field normal modes become Anderson-localized, giving rise to a non-Markovian atomic dynamics. We show the existence of a functional relationship between a rigorous measure of quantum non-Markovianity and the CCA localization. We furthermore show that the average non-Markovianity of the atomic dynamics is well-described by a phenomenological model in which the atom is coupled, at the same time, to a single mode and to a standard - Markovian - dissipative bath

Taxonomic remarks and distribution of Smyrnium dimartinoi (Apiaceae)

Smyrnium L., an Eurasian genus of the family Apiaceae, includes about 20 taxa of which only 7 are accepted at specific rank; among these, 5 are native to Europe (Tutin & al. 1968; Gomez 2003). In the Italian flora, the genus is represented by 3 taxa also occurring in Sicily (Pignatti 1982; Giardina & al. 2007); these are Smyrnium olusatrum L., S. perfoliatum L. and S. rotundifolium Mill. The last one has also been treated at the rank of subspecies under S. perfoliatum [S. perfoliatum subsp. rotundifolium (Mill.) Hartvig] (Strid 1986; Conti & al. 2005), or as a variety [S. perfoliatum var. rotundifolium (Mill.)Fiori (Fiori 1925)]. In Sicily, same populations related to S. perfoliatum differ from this taxon for both morphological and ecological characteristics, especially on the Madonie Mountains and the Mountains around Palermo. The study of the morphological characteristics \u2013 namely of the root, stem, and leaf \u2013 allowed to clearly distinguish these populations that, therefore, represented a taxonomically and perhaps even chorologically critical case, since similar plants occurring in Greece were described as S. rotundifolium var. ovatifolium Hal\ue1csy (Hal\ue1csy 1901). In Sicily the same population was finally described as a new species named Smyrnium dimartinoi (Raimondo et al., 2015) to commemorate Andrea Di Martino (1926-2009), professor of botany and director of the Botanical Garden and Herbarium Mediterraneum in the Palermo University. The occurrence of the new taxon related to S. perfoliatum \u2013 ascertained only in Central-Western Sicily and in Crete \u2013 has also been supposed in other countries of the Mediterranean Europe; this, owing to some critical specimens observed in PAL and PAL-Gr. In this contribution, the analytical key of S. perfoliatum group is presented. Furthermore, the geographical distribution of S. dimartinoi is specified after the study of selected exsiccata from other Italian and foreign herbaria. The results found in this research show that S. dimartinoi belongs to the Eurimediterranean element, spread in various countries of the Southern Europe, from Greece to Italy and Spain

Physical model for the generation of ideal resources in multipartite quantum networking

We propose a physical model for generating multipartite entangled states of spin-$s$ particles that have important applications in distributed quantum information processing. Our protocol is based on a process where mobile spins induce the interaction among remote scattering centers. As such, a major advantage lies on the management of stationary and well separated spins. Among the generable states, there is a class of $N$-qubit singlets allowing for optimal quantum telecloning in a scalable and controllable way. We also show how to prepare Aharonov, W and Greenberger-Horne-Zeilinger states.Comment: 5 pages, 2 figures. Format revise