Electron teleportation with quantum dot arrays

An electron teleportation protocol, inspired by the scenario by Bennett et al., is proposed in a mesoscopic set-up. A superconducting circuit allows to both inject and measure entangled singlet electron pairs in an array of three normal quantum dots. The selection of the teleportation process is achieved in the steady state with the help of two superconducting dots and appropriate gating. Teleportation of the electron spin is detected by measuring the spin-polarized current through the normal dot array. This current is perfectly correlated to the pair current flowing inside the superconducting circuit. The classical channel required by Bennett's protocol, which signals the completion of a teleportation cycle, is identified with the detection of an electron charge in the superconducting circuit.Comment: revised version, 4 pages, 2 figure

Failure of mean-field approach in out-of-equilibrium Anderson model

To explore the limitations of the mean field approximation, frequently used in \textit{ab initio} molecular electronics calculations, we study an out-of-equilibrium Anderson impurity model in a scattering formalism. We find regions in the parameter space where both magnetic and non-magnetic solutions are stable. We also observe a hysteresis in the non-equilibrium magnetization and current as a function of the applied bias voltage. The mean field method also predicts incorrectly local moment formation for large biases and a spin polarized current, and unphysical kinks appear in various physical quantities. The mean field approximation thus fails in every region where it predicts local moment formation.Comment: 5 pages, 5 figure

Teleportation in a noisy environment: a quantum trajectories approach

We study the fidelity of quantum teleportation for the situation in which quantum logic gates are used to provide the long distance entanglement required in the protocol, and where the effect of a noisy environment is modeled by means of a generalized amplitude damping channel. Our results demonstrate the effectiveness of the quantum trajectories approach, which allows the simulation of open systems with a large number of qubits (up to 24). This shows that the method is suitable for modeling quantum information protocols in realistic environments.Comment: 9 pages, 2 figure

Quantum teleportation by particle-hole annihilation in the Fermi sea

A tunnel barrier in a degenerate electron gas was recently discovered as a source of entangled particle-hole excitations. The entanglement is produced by elastic tunneling events, without requiring electron-electron interactions. Here we investigate the inverse process, the annihilation of an electron and a hole by elastic scattering. We find that this process leads to teleportation of the (unknown) state of the annihilated electron to a second, distant electron -- if the latter was previously entangled with the annihilated hole. We propose an experiment, involving low-frequency noise measurements on a two-dimensional electron gas in a high magnetic field, to detect teleportation of electrons and holes in the two lowest Landau levels.Comment: 5 pages including 2 figures; [2017: fixed broken postscript figures

Spin current shot noise as a probe of interactions in mesoscopic systems

It is shown that the spin resolved current shot noise can probe attractive or repulsive interactions in mesoscopic systems. This is illustrated in two physical situations : i) a normal-superconducting junction where the spin current noise is found to be zero, and ii) a single electron transistor (SET), where the spin current noise is found to be Poissonian. Repulsive interactions may also lead to weak attractive correlations (bunching of opposite spins) in conditions far from equilibrium. Spin current shot noise can be used to measure the spin relaxation time $T_1$, and a set-up is proposed in a quantum dot geometry.Comment: 5 pages, 4 Figures, revised version, added reference

Toy models of crossed Andreev reflection

We propose toy models of crossed Andreev reflection in multiterminal hybrid structures containing out-of-equilibrium conductors. We apply the description to two possible experiments: (i) to a device containing a large quantum dot inserted in a crossed Andreev reflection circuit. (ii) To a device containing an Aharonov-Bohm loop inserted in a crossed Andreev reflection circuit.Comment: 5 pages, 9 figures, minor modification

An optimised transformation protocol for Anthoceros agrestis and three more hornwort species

Land plants comprise two large monophyletic lineages, the vascular plants and the bryophytes, which diverged from their most recent common ancestor approximately 480 million years ago. Of the three lineages of bryophytes, only the mosses and the liverworts are systematically investigated, while the hornworts are understudied. Despite their importance for understanding fundamental questions of land plant evolution, they only recently became amenable to experimental investigation, with Anthoceros agrestis being developed as a hornwort model system. Availability of a high-quality genome assembly and a recently developed genetic transformation technique makes A. agrestis an attractive model species for hornworts. Here we describe an updated and optimised transformation protocol for A. agrestis which can be successfully used to genetically modify one more strain of A. agrestis and three more hornwort species, Anthoceros punctatus, Leiosporoceros dussi and Phaeoceros carolinianus. The new transformation method is less laborious, faster and results in the generation of greatly increased numbers of transformants compared to the previous method. We have also developed a new selection marker for transformation. Finally, we report the development of a set of different cellular localisation signal peptides for hornworts providing new tools to better understand hornwort cell biology

Quasiparticle entanglement: redefinition of the vacuum and reduced density matrix approach

A scattering approach to entanglement in mesoscopic conductors with independent fermionic quasiparticles is discussed. We focus on conductors in the tunneling limit, where a redefinition of the quasiparticle vacuum transforms the wavefunction from a manybody product state of noninteracting particles to a state describing entangled two-particle excitations out of the new vacuum. The approach is illustrated with two examples (i) a normal-superconducting system, where the transformation is made between Bogoliubov-de Gennes quasiparticles and Cooper pairs, and (ii) a normal system, where the transformation is made between electron quasiparticles and electron-hole pairs. This is compared to a scheme where an effective two-particle state is derived from the manybody scattering state by a reduced density matrix approach.Comment: Submitted to New Journal of Physics, Focused Issue on "Solid State Quantum Information". 19 pages, 7 figure

Clinical Characteristics and Treatment Outcomes of Mycobacterium kansasii Lung Disease in Korea

*These authors contributed equally to this work. ∙The authors have no financial conflicts of interest. Purpose: While Mycobacterium kansasii is a common cause of nontuberculous mycobacterial (NTM) lung disease in many developed countries, M. kansasii is infrequently isolated in Korea. We investigated the clinical and radiological features and treatment outcomes of M. kansasii lung disease in Korea retrospectively. Materials and Methods: We identified 41 patients with M. kansasii lung disease who met the diagnostic criteria for NTM lung disease in two tertiary referral hospitals in Seoul, Korea, between January 1998 and December 2007. Results: Their median age was 63 years [interquartile range (IQR) 51-75 years] and 33 (81%) were men. Twenty-three patients (56%) were smokers and 13 patients (32%) had previous pulmonary tuberculosis. The most common radiographic findings were nodules (n = 22, 54%) and consolidation (n = 22, 54%). Cavitation was present in 13 patients (32%). Thirty-one patients (76%) were treated with isoniazid, rifampin, and ethambutol. The median treatment duration was 16 months (IQR 9-18 months). The negative conversion rate after 12 months of treatment was 95%. Conclusion: Clinicians should be aware of the various radiographic manifestations of M. kansasii lung disease. With appropriate treatment, these patients have a good prognosis

Crossed Andreev reflection at ferromagnetic domain walls

We investigate several factors controlling the physics of hybrid structures involving ferromagnetic domain walls (DWs) and superconducting (S) metals. We discuss the role of non collinear magnetizations in S/DW junctions in a spin $\otimes$ Nambu $\otimes$ Keldysh formalism. We discuss transport in S/DW/N and S/DW/S junctions in the presence of inelastic scattering in the domain wall. In this case transport properties are similar for the S/DW/S and S/DW/N junctions and are controlled by sequential tunneling of spatially separated Cooper pairs across the domain wall. In the absence of inelastic scattering we find that a Josephson current circulates only if the size of the ferromagnetic region is smaller than the elastic mean free path meaning that the Josephson effect associated to crossed Andreev reflection cannot be observed under usual experimental conditions. Nevertheless a finite dc current can circulate across the S/DW/S junction due to crossed Andreev reflection associated to sequential tunneling.Comment: 18 pages, 8 figures, references added at the end of the introductio