Good approximate quantum LDPC codes from spacetime circuit Hamiltonians

We study approximate quantum low-density parity-check (QLDPC) codes, which are approximate quantum error-correcting codes specified as the ground space of a frustration-free local Hamiltonian, whose terms do not necessarily commute. Such codes generalize stabilizer QLDPC codes, which are exact quantum error-correcting codes with sparse, low-weight stabilizer generators (i.e. each stabilizer generator acts on a few qubits, and each qubit participates in a few stabilizer generators). Our investigation is motivated by an important question in Hamiltonian complexity and quantum coding theory: do stabilizer QLDPC codes with constant rate, linear distance, and constant-weight stabilizers exist? We show that obtaining such optimal scaling of parameters (modulo polylogarithmic corrections) is possible if we go beyond stabilizer codes: we prove the existence of a family of $[[N,k,d,\varepsilon]]$ approximate QLDPC codes that encode $k = \widetilde{\Omega}(N)$ logical qubits into $N$ physical qubits with distance $d = \widetilde{\Omega}(N)$ and approximation infidelity $\varepsilon = \mathcal{O}(1/\textrm{polylog}(N))$. The code space is stabilized by a set of 10-local noncommuting projectors, with each physical qubit only participating in $\mathcal{O}(\textrm{polylog} N)$ projectors. We prove the existence of an efficient encoding map, and we show that arbitrary Pauli errors can be locally detected by circuits of polylogarithmic depth. Finally, we show that the spectral gap of the code Hamiltonian is $\widetilde{\Omega}(N^{-3.09})$ by analyzing a spacetime circuit-to-Hamiltonian construction for a bitonic sorting network architecture that is spatially local in $\textrm{polylog}(N)$ dimensions.Comment: 51 pages, 13 figure

The nuclear pattern of the non-tectal portions of the midbrain and isthmus in the shrew and the bat

No Abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49934/1/900780307_ftp.pd

Quantifying and resolving multiple vector transformants in S. cerevisiae plasmid libraries

<p>Abstract</p> <p>Background</p> <p>In addition to providing the molecular machinery for transcription and translation, recombinant microbial expression hosts maintain the critical genotype-phenotype link that is essential for high throughput screening and recovery of proteins encoded by plasmid libraries. It is known that <it>Escherichia coli </it>cells can be simultaneously transformed with multiple unique plasmids and thusly complicate recombinant library screening experiments. As a result of their potential to yield misleading results, bacterial multiple vector transformants have been thoroughly characterized in previous model studies. In contrast to bacterial systems, there is little quantitative information available regarding multiple vector transformants in yeast. <it>Saccharomyces cerevisiae </it>is the most widely used eukaryotic platform for cell surface display, combinatorial protein engineering, and other recombinant library screens. In order to characterize the extent and nature of multiple vector transformants in this important host, plasmid-born gene libraries constructed by yeast homologous recombination were analyzed by DNA sequencing.</p> <p>Results</p> <p>It was found that up to 90% of clones in yeast homologous recombination libraries may be multiple vector transformants, that on average these clones bear four or more unique mutant genes, and that these multiple vector cells persist as a significant proportion of library populations for greater than 24 hours during liquid outgrowth. Both vector concentration and vector to insert ratio influenced the library proportion of multiple vector transformants, but their population frequency was independent of transformation efficiency. Interestingly, the average number of plasmids born by multiple vector transformants did not vary with their library population proportion.</p> <p>Conclusion</p> <p>These results highlight the potential for multiple vector transformants to dominate yeast libraries constructed by homologous recombination. The previously unrecognized prevalence and persistence of multiply transformed yeast cells have important implications for yeast library screens. The quantitative information described herein should increase awareness of this issue, and the rapid sequencing approach developed for these studies should be widely useful for identifying multiple vector transformants and avoiding complications associated with cells that have acquired more than one unique plasmid.</p

HI Global Scaling Relations in the WISE-WHISP Survey

We present the global scaling relations between the neutral atomic hydrogen gas, the stellar disk and the star forming disk in a sample of 228 nearby galaxies that are both spatially and spectrally resolved in HI line emission. We have used HI data from the Westerbork survey of HI in Irregular and Spiral galaxies (WHISP) and Mid Infrared (3.4 $\mu m$, 11.6 $\mu m$) data from the Wide-field Infrared Survey Explorer (WISE) survey, combining two datasets that are well-suited to such a study in terms of uniformity, resolution and sensitivity. We utilize the novel method of deriving scaling relations for quantities enclosed within the stellar disk rather than integrating over the HI disk and find the global scaling relations to be tighter when defined for enclosed quantities. We also present new HI intensity maps for the WHISP survey derived using a robust noise rejection technique along with corresponding velocity fields.Comment: 18 pages, 5 tables, 16 Figures. Accepted for publication in the Monthly Notices of the Royal Astronomical Society. Minor revisio

Extremely Red Objects in Two Quasar Fields at z ~ 1.5

We present an investigation of the properties and environments of bright extremely red objects (EROs) found in the fields of the quasars TXS 0145+386 and 4C 15.55, both at z ~ 1.4. There is marginal evidence from Chandra ACIS imaging for hot cluster gas with a luminosity of a few 10^44 ergs/s in the field of 4C 15.55. The TXS 0145+386 field has an upper limit at a similar value, but it also clearly shows an overdensity of faint galaxies. None of the EROs are detected as X-ray sources. For two of the EROs that have spectral-energy distributions and rest-frame near-UV spectra that show that they are strongly dominated by old stellar populations, we determine radial-surface-brightness profiles from adaptive-optics images. Both of these galaxies are best fit by profiles close to exponentials, plus a compact nucleus comprising ~30% of the total light in one case and 8% in the other. Neither is well fit by an r^1/4-law profile. This apparent evidence for the formation of massive ~2 X 10^11 disks of old stars in the early universe indicates that at least some galaxies formed essentially monolithically, with high star-formation rates sustained over a few 10^8 years, and without the aid of major mergers.Comment: 25 pages, 13 figures, accepted to Ap

Social work as a career choice (a study of selected variables in the choice of social work as a career)

Thesis (M.S.)--Boston Universit

Sodium content as a predictor of the advanced evolution of globular cluster stars

The asymptotic giant branch (AGB) phase is the final stage of nuclear burning for low-mass stars. Although Milky Way globular clusters are now known to harbour (at least) two generations of stars they still provide relatively homogeneous samples of stars that are used to constrain stellar evolution theory. It is predicted by stellar models that the majority of cluster stars with masses around the current turn-off mass (that is, the mass of the stars that are currently leaving the main sequence phase) will evolve through the AGB phase. Here we report that all of the second-generation stars in the globular cluster NGC 6752 -- 70 per cent of the cluster population -- fail to reach the AGB phase. Through spectroscopic abundance measurements, we found that every AGB star in our sample has a low sodium abundance, indicating that they are exclusively first-generation stars. This implies that many clusters cannot reliably be used for star counts to test stellar evolution timescales if the AGB population is included. We have no clear explanation for this observation.Comment: Published in Nature (online 29 May 2013, hard copy 13 June), 12 pages, 3 figures + supplementary information sectio

Do Prosecutors Use Interview Instructions or Build Rapport with Child Witnesses?

This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/bsl.2183This study examined the quality of interview instructions and rapport-building provided by prosecutors to 168 children aged 5-12 years testifying in child sexual abuse cases, preceding explicit questions about abuse allegations. Prosecutors failed to effectively administer key interview instructions, build rapport, or rely on open-ended narrative producing prompts during this early stage of questioning. Moreover, prosecutors often directed children's attention to the defendant early in the testimony. The productivity of different types of wh- questions varied, with what/how questions focusing on actions being particularly productive. The lack of instructions, poor quality rapport-building, and closed-ended questioning suggest that children may not be adequately prepared during trial to provide lengthy and reliable reports to their full ability.This research was supported by NICHD Grant HD047290 to Dr. Thomas Lyon

Building Capacity in Nonprofit Organizations

Offers a capacity building model that is based on a review of civil society, sustainable development, and organizational management literature. Reviews effective capacity building programs sponsored or operated by foundations. Includes recommendations