Cloning a Qutrit

We investigate several classes of state-dependent quantum cloners for three-level systems. These cloners optimally duplicate some of the four maximally-conjugate bases with an equal fidelity, thereby extending the phase-covariant qubit cloner to qutrits. Three distinct classes of qutrit cloners can be distinguished, depending on two, three, or four maximally-conjugate bases are cloned as well (the latter case simply corresponds to the universal qutrit cloner). These results apply to symmetric as well as asymmetric cloners, so that the balance between the fidelity of the two clones can also be analyzed.Comment: 14 pages LaTex. To appear in the Journal of Modern Optics for the special issue on "Quantum Information: Theory, Experiment and Perspectives". Proceedings of the ESF Conference, Gdansk, July 10-18, 200

Flexible quantum circuits using scalable continuous-variable cluster states

We show that measurement-based quantum computation on scalable continuous-variable (CV) cluster states admits more quantum-circuit flexibility and compactness than similar protocols for standard square-lattice CV cluster states. This advantage is a direct result of the macronode structure of these states---that is, a lattice structure in which each graph node actually consists of several physical modes. These extra modes provide additional measurement degrees of freedom at each graph location, which can be used to manipulate the flow and processing of quantum information more robustly and with additional flexibility that is not available on an ordinary lattice.Comment: (v2) consistent with published version; (v1) 11 pages (9 figures

Further Criteria for the Existence of Steady Line-Driven Winds

In Paper I, we showed that steady line-driven disk wind solutions can exist by using "simple" models that mimic the disk environment. Here I extend the concepts introduced in Paper I and discuss many details of the analysis of the steady/unsteady nature of 1D line-driven winds. This work confirms the results and conclusions of Paper I, and is thus consistent with the steady nature of the 1D streamline line-driven disk wind models of Murray and collaborators and the 2.5D line-driven disk wind models of Pereyra and collaborators. When including gas pressures effects, as is routinely done in time-dependent numerical models, I find that the spatial dependence of the nozzle function continues to play a key role in determining the steady/unsteady nature of supersonic line-driven wind solutions. I show here that the existence/nonexistence of local wind solutions can be proved through the nozzle function without integrating the equation of motion. This work sets a detailed framework with which we will analyze, in a following paper, more realistic models than the "simple" models of Paper I.Comment: 30 pages, 5 figures, accepted for publication by The Astrophysical Journa

Error Analysis of Phonetic Fossilization Uttered by English Department Students University of PGRI Semarang

Penelitian ini bertujuan untuk menentukan tipe dan latar belakang fosilisasi fonetik yang diucapkan oleh mahasiswa semester 5 Pendidikan Bahasa Inggris di Universitas PGRI Semarang tahun 2014/2015. Penelitian ini menggunakan desain penelitian deskriptif dengan data kualitatif. Populasi dari penelitian ini adalah para mahasiswa semester 5 yang mengambil mata kuliah English Phonology dengan jumlahmahasiswa 200. Sampel penelitian adalah kelas 5E, kelas yang paling aktif dan dominan.Hasil penelitian menunjukkan bahwa hanya 15% kata di dalam kuesioner penelitian yang berhasil dilafalkan dengan baik oleh para responden. Itu artinya bahwa fosilisasi fonetik dilakukan lebih dari 75% responden. Tipe kesalahan yang dibuat adalah tipe fosilisasi fonetik baik dalam kategori perseorangan maupun kelompok, sementara itu alasan-alasan mereka melakukan kesalahan adalah; 1)Simbol fonetik yang masih tidak familier bagi mahasiswa semester. 2) Terdapat habituasi dan kebiasaan-kebiasaan yang merujuk pada dua faktor: internal dan eksternal. Faktor internalnya adalah mahasiswa itu sendiri, yang berarti motivasi untuk belajar dan hasrat untuk lebih dalam mempelajari simbol -simbol fonetik. Faktor eksternalnya merujuk pada proses pembelajaran dan sudut pandang dosen. 3) Metode yang digunakan oleh para dosen pengampu mata kuliah English Phonology and Pronounciation. Masalah ini harus diturunkan karena 90% dari mahasiswa menyatakan di dalam wawancara bahwa mereka sangat tertarik dengan subjek ini danjuga menyatakan bahwa para dosen tidak memberikan tekanan, namun faktanya persentase kesalahan dalam pelafalan di atas rata-rata.Berdasarkan pada hasil-haasil ini, peneliti memberika saran sebagai berikut; 1) Permasalahan ini menjadi tugas bagi seluruh dosen bahasa Inggris, tidak hanya dosen yang mengajar mata kuliah English Phonology and Pronunciation. 2) Simbolsimbol fonetik harus diterapkan secara intensif dan integral sehingga para mahasiswa dapat familier dengan simbol-simbol tersebut. 3) Kebutuhan akan penelitian lebih lanjut yang terkait dengan metode-metode yang digunakan oleh para dosen

Astrophysical and Dark Matter Interpretations of Extended Gamma-Ray Emission from the Galactic Center

We construct empirical models of the diffuse gamma-ray background toward the Galactic Center. Including all known point sources and a template of emission associated with interactions of cosmic rays with molecular gas, we show that the extended emission observed previously in the Fermi Large Area Telescope data toward the Galactic Center is detected at high significance for all permutations of the diffuse model components. However, we find that the fluxes and spectra of the sources in our model change significantly depending on the background model. In particular, the spectrum of the central Sgr A$^\ast$ source is less steep than in previous works and the recovered spectrum of the extended emission has large systematic uncertainties, especially at lower energies. If the extended emission is interpreted to be due to dark matter annihilation, we find annihilation into pure $b$-quark and $\tau$-lepton channels to be statistically equivalent goodness of fits. In the case of the pure $b$-quark channel, we find a dark matter mass of $39.4\left(^{+3.7}_{-2.9}\rm\ stat.\right)\left(\pm 7.9\rm\ sys.\right)\rm\ GeV$, while a pure$\tau^{+} \tau^{-}$-channel case has an estimated dark matter mass of$9.43\left(^{+0.63}_{-0.52}\rm\ stat.\right)(\pm 1.2\rm\ sys.)\ GeV$. Alternatively, if the extended emission is interpreted to be astrophysical in origin such as due to unresolved millisecond pulsars, we obtain strong bounds on dark matter annihilation, although systematic uncertainties due to the dependence on the background models are significant.Comment: 14 pages, 11 figures; v3: matches version in Phys. Rev.

Dimensional reduction in nonlinear filtering: A homogenization approach

We propose a homogenized filter for multiscale signals, which allows us to reduce the dimension of the system. We prove that the nonlinear filter converges to our homogenized filter with rate $\sqrt{\varepsilon}$. This is achieved by a suitable asymptotic expansion of the dual of the Zakai equation, and by probabilistically representing the correction terms with the help of BDSDEs.Comment: Published in at http://dx.doi.org/10.1214/12-AAP901 the Annals of Applied Probability (http://www.imstat.org/aap/) by the Institute of Mathematical Statistics (http://www.imstat.org

A No-Go Theorem for Gaussian Quantum Error Correction

It is proven that Gaussian operations are of no use for protecting Gaussian states against Gaussian errors in quantum communication protocols. Specifically, we introduce a new quantity characterizing any single-mode Gaussian channel, called entanglement degradation, and show that it cannot decrease via Gaussian encoding and decoding operations only. The strength of this no-go theorem is illustrated with some examples of Gaussian channels.Comment: 4 pages, 2 figures, REVTeX

The dynamics of copper intercalated molybdenum ditelluride

Layered transition metal dichalcogenides are emerging as key materials in nanoelectronics and energy applications. Predictive models to understand their growth, thermomechanical properties and interactions with metals are needed in order to accelerate their incorporation into commercial products. Interatomic potentials enable large-scale atomistic simulations at the device level, beyond the range of applications of first principle methods. We present a ReaxFF reactive force field to describe molybdenum ditelluride and its interactions with copper. We optimized the force field parameters to describe the properties of layered MoTe2 in various phases, the intercalation of Cu atoms and clusters within its van der Waals gap, including a proper description of energetics, charges and mechanical properties. The training set consists of an extensive set of first principle calculations computed from density functional theory. We use the force field to study the adhesion of a single layer MoTe2 on a Cu(111) surface and the results are in good agreement with density functional theory, even though such structures were not part of the training set. We characterized the mobility of the Cu ions intercalated into MoTe2 under the presence of an external electric fields via molecular dynamics simulations. The results show a significant increase in drift velocity for electric fields of approximately 0.4 V/A and that mobility increases with Cu ion concentration.Comment: 21 pages, 9 Figure