Practical characterization of quantum devices without tomography

Quantum tomography is the main method used to assess the quality of quantum information processing devices, but its complexity presents a major obstacle for the characterization of even moderately large systems. The number of experimental settings required to extract complete information about a device grows exponentially with its size, and so does the running time for processing the data generated by these experiments. Part of the problem is that tomography generates much more information than is usually sought. Taking a more targeted approach, we develop schemes that enable (i) estimating the fidelity of an experiment to a theoretical ideal description, (ii) learning which description within a reduced subset best matches the experimental data. Both these approaches yield a significant reduction in resources compared to tomography. In particular, we demonstrate that fidelity can be estimated from a number of simple experimental settings that is independent of the system size, removing an important roadblock for the experimental study of larger quantum information processing units.Comment: (v1) 11 pages, 1 table, 4 figures. (v2) See also the closely related work: arXiv:1104.4695 (v3) method extended to continuous variable systems (v4) updated to published versio

Pengaruh Kualitas Pelayanan terhadap Kepuasan Pemohon Surat Izin Mengemudi (SIM) pada Satuan Lalulintas Polresta Gunung Sitoli

Penelitian ini bertujuan untuk mengetahui pengaruh kualitas pelayanan terhadap kepuasan pemohon Surat Izin Mengemudi (SIM) pada satuan lalulintas Polresta Gunung Sitoli. Penelitian ini dilakukan pada Satuan Lalulintas (Satlantas) Polresta Gunung Sitoli, yang dilaksanakan pada bulan Agustus hingga September 2018. Jumlah sampel penelitian ini ditetapkan sebanyak 100 orang pemohon SIM pada Satlantas Polresta Gunung Sitoli. Variabel penelitian ini terdiri dari variabel bebas dan terikat. Variabel bebas dalam peneitian ini adalah kualitas pelayanan (X). Sedangkan variabel terikat adalah kepuasan masyarakat (Y). Analisis data menggunakan analisis regresi sederhana. Hasil penelitian menunjukkan bahwa kualitas pelayanan pada Satuan Lalu Lintas Polresta Gunung Sitoli tergolong cukup baik dan baik dan masih terdapat, sehingga perlu peningkatan kualitas pelayanan. Kepuasan masyarakat pemohon SIM pada Satuan Lalu Lintas Polresta Gunung Sitoli sudah tergolong cukup baik dan baik, tetapi masih dapat ditingkatkan menjadi sangat baik. Kualitas pelayanan mempunyai pengaruh yang positif terhadap kepuasan masyarakat pemohon SIM, artinya apabila kualitas pelayanan meningkat maka akan diikuti oleh peningkatan kepuasan masyarakat pemohon SIM

Pengaruh Program Nasional Pemberdayaan Masyarakat Mandiri Perdesaan terhadap Sosial Ekonomi Rumah Tangga pada Kelompok Simpan Pinjam Perempuan di Desa Ononamolo II Lot Kecamatan Gunungsitoli Barat Kota Gunungsitoli

Poverty is a phenomenal problem. Therefore, poverty is a topic that is very important and crucial to be completed. The phenomenon of poverty, which is most often found in rural areas, has been undertaken by the government to be resolved by establishing programs such as the National Program for Community Empowerment in Rural Areas or Program Nasional Pemberdayaan Masyarakat Mandiri Perdesaan (PNPM-MP), as a solution. This study research has the objective to determine the effect of this program on socio-economic conditions of the household in the group of women on savings and loan in Ononamolo II Lot Village, sub-district of West Gunungsitoli, Gunungsitoli. This research study considered in a descriptive study by using descriptive statistical analysis. The population in this research study were 40 women who participated in the activities savings and loan for women in Ononamolo II Lot Village, with the presentation of the data using a single table system. Methods of data collection are questionnaires, interviews, real observations, and literature study. The results showed that the influence of PNPM-MP for the socio-economic of the household in the group of women on savings and loan in Ononamolo II Lot Village, sub-district of West Gunungsitoli, Gunungsitoli, is less influential. This is caused by the lack of education that have an impact on the lack of management of the loans, the lack of participation of members of the group, and the lack of oversight by the management

Colorful Strips

Given a planar point set and an integer $k$, we wish to color the points with $k$ colors so that any axis-aligned strip containing enough points contains all colors. The goal is to bound the necessary size of such a strip, as a function of $k$. We show that if the strip size is at least $2k{-}1$, such a coloring can always be found. We prove that the size of the strip is also bounded in any fixed number of dimensions. In contrast to the planar case, we show that deciding whether a 3D point set can be 2-colored so that any strip containing at least three points contains both colors is NP-complete. We also consider the problem of coloring a given set of axis-aligned strips, so that any sufficiently covered point in the plane is covered by $k$ colors. We show that in $d$ dimensions the required coverage is at most $d(k{-}1)+1$. Lower bounds are given for the two problems. This complements recent impossibility results on decomposition of strip coverings with arbitrary orientations. Finally, we study a variant where strips are replaced by wedges

Large Coercivity in Nanostructured Rare-earth-free MnxGa Films

The magnetic hysteresis of MnxGa films exhibit remarkably large coercive fields as high as 2.5 T when fabricated with nanoscale particles of a suitable size and orientation. This coercivity is an order of magnitude larger than in well-ordered epitaxial film counterparts and bulk materials. The enhanced coercivity is attributed to the combination of large magnetocrystalline anisotropy and ~ 50 nm size nanoparticles. The large coercivity is also replicated in the electrical properties through the anomalous Hall effect. The magnitude of the coercivity approaches that found in rare-earth magnets, making them attractive for rare-earth-free magnet applications

Decoherence suppression via environment preparation

To protect a quantum system from decoherence due to interaction with its environment, we investigate the existence of initial states of the environment allowing for decoherence-free evolution of the system. For models in which a two-state system interacts with a dynamical environment, we prove that such states exist if and only if the interaction and self-evolution Hamiltonians share an eigenstate. If decoherence by state preparation is not possible, we show that initial states minimizing decoherence result from a delicate compromise between the environment and interaction dynamics.Comment: 4 pages, 2 figure

Unsplittable coverings in the plane

A system of sets forms an {\em $m$-fold covering} of a set $X$ if every point of $X$ belongs to at least $m$ of its members. A $1$-fold covering is called a {\em covering}. The problem of splitting multiple coverings into several coverings was motivated by classical density estimates for {\em sphere packings} as well as by the {\em planar sensor cover problem}. It has been the prevailing conjecture for 35 years (settled in many special cases) that for every plane convex body $C$, there exists a constant $m=m(C)$ such that every $m$-fold covering of the plane with translates of $C$ splits into $2$ coverings. In the present paper, it is proved that this conjecture is false for the unit disk. The proof can be generalized to construct, for every $m$, an unsplittable $m$-fold covering of the plane with translates of any open convex body $C$ which has a smooth boundary with everywhere {\em positive curvature}. Somewhat surprisingly, {\em unbounded} open convex sets $C$ do not misbehave, they satisfy the conjecture: every $3$-fold covering of any region of the plane by translates of such a set $C$ splits into two coverings. To establish this result, we prove a general coloring theorem for hypergraphs of a special type: {\em shift-chains}. We also show that there is a constant $c>0$ such that, for any positive integer $m$, every $m$-fold covering of a region with unit disks splits into two coverings, provided that every point is covered by {\em at most} $c2^{m/2}$ sets

Optical Propagation and Communication

Contains research objectives and summary of research on four research projects.National Aeronautics and Space Administration (Grant NGR 22-009-013)U.S. Navy - Office of Naval Research (Contract N00014-76-C-0605)Joint Services Electronics Program (Contract DAAB07-76-C-1400)National Science Foundation (Grant ENG74-00131-AO2)U. S. Air Force - Electronic Systems Division (Contract F19628-76-C-0054)National Science Foundation (Grant ENG74-03996-A1

Coherent acoustic vibration of metal nanoshells

Using time-resolved pump-probe spectroscopy we have performed the first investigation of the vibrational modes of gold nanoshells. The fundamental isotropic mode launched by a femtosecond pump pulse manifests itself in a pronounced time-domain modulation of the differential transmission probed at the frequency of nanoshell surface plasmon resonance. The modulation amplitude is significantly stronger and the period is longer than in a gold nanoparticle of the same overall size, in agreement with theoretical calculations. This distinct acoustical signature of nanoshells provides a new and efficient method for identifying these versatile nanostructures and for studying their mechanical and structural properties.Comment: 5 pages, 3 figure

Asymptotic behaviour of estimators of the parameters of nearly unstable INAR(1) models

A sequence of first-order integer-valued autoregressive type (INAR(1)) processes is investigated, where the autoregressive type coefficients converge to 1. It is shown that the limiting distribution of the joint conditional least squares estimators for this coefficient and for the mean of the innovation is normal. Consequences for sequences of Galton{Watson branching processes with unobservable immigration, where the mean of the offspring distribution converges to 1 (which is the critical value), are discussed