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

Improving SPAWAR PEO C4I organizational alignment to better enable enterprise technical risk management

This thesis examined how the Navy's Program Executive Office Command, Control, Communications, Computers and Intelligence (PEO C4I) has performed enterprise risk management (ERM). Based on ERM literature, the study developed an analytical framework to assess PEO C4I's ERM practices against documented ERM best practices, including evaluating a new risk in terms of its impact on existing risks and ensuring risks are managed at the most detailed level possible. The thesis also utilized organizational alignment literature to include organizational alignment principles in the evaluation. Key principles include 1) every employee has the responsibility to manage risk and 2) multiple teams are able to manage a single risk. The resultant analytical framework was applied to PEO C4I and documented for application to other organizations. PEO C4I performed well in the areas of 1) evaluating risks in areas other than the originating program office and 2) providing the framework to elevate risks to leadership. PEO C4I could use improvement in cross-team risk coordination and development of enterprise models to provide context for enterprise risks. Recommended interventions focus on having more functional areas involved in risk mitigation and developing a common enterprise architecture to improve understanding of potential areas of risk.http://archive.org/details/improvingspawarp1094552965Civilian, Department of the NavyApproved for public release; distribution is unlimited

Panel Discussion - Management of Eurasian watermilfoil in the United States using native insects: State regulatory and management issues

While researchers have evaluated the potential of native insect herbivores to manage nonindigenous aquatic plant species such as Eurasian watermilfoil ( Myriophyllum spicatum L.), the practical matters of regulatory compliance and implementation have been neglected. A panel of aquatic nuisance species program managers from three state natural resource management agencies (Minnesota, Vermont and Washington) discussed their regulatory and policy concerns. In addition, one ecological consultant attempting to market one of the native insects to manage Eurasian watermilfoil added his perspective on the special challenges of distributing a native biological control agent for management of Eurasian watermilfoil

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,ε]] approximate QLDPC codes that encode k = Ω(N) logical qubits into N physical qubits with distance d = Ω(N) and approximation infidelity ε = 1/(N). The code space is stabilized by a set of 10-local noncommuting projectors, with each physical qubit only participating in N projectors. We prove the existence of an efficient encoding map and show that the spectral gap of the code Hamiltonian scales as Ω(N^(−3.09)). We also show that arbitrary Pauli errors can be locally detected by circuits of polylogarithmic depth. Our family of approximate QLDPC codes is based on applying a recent connection between circuit Hamiltonians and approximate quantum codes (Nirkhe, et al., ICALP 2018) to a result showing that random Clifford circuits of polylogarithmic depth yield asymptotically good quantum codes (Brown and Fawzi, ISIT 2013). Then, in order to obtain a code with sparse checks and strong detection of local errors, we use a spacetime circuit-to-Hamiltonian construction in order to take advantage of the parallelism of the Brown-Fawzi circuits. Because of this, we call our codes spacetime codes. The analysis of the spectral gap of the code Hamiltonian is the main technical contribution of this work. We show that for any depth D quantum circuit on n qubits there is an associated spacetime circuit-to-Hamiltonian construction with spectral gap Ω(n^(−3.09)D⁻² log⁻⁶ (n)). To lower bound this gap we use a Markov chain decomposition method to divide the state space of partially completed circuit configurations into overlapping subsets corresponding to uniform circuit segments of depth logn, which are based on bitonic sorting circuits. We use the combinatorial properties of these circuit configurations to show rapid mixing between the subsets, and within the subsets we develop a novel isomorphism between the local update Markov chain on bitonic circuit configurations and the edge-flip Markov chain on equal-area dyadic tilings, whose mixing time was recently shown to be polynomial (Cannon, Levin, and Stauffer, RANDOM 2017). Previous lower bounds on the spectral gap of spacetime circuit Hamiltonians have all been based on a connection to exactly solvable quantum spin chains and applied only to 1+1 dimensional nearest-neighbor quantum circuits with at least linear depth

Reading aloud boosts connectivity through the putamen

Functional neuroimaging and lesion studies have frequently reported thalamic and putamen activation during reading and speech production. However, it is currently unknown how activity in these structures interacts with that in other reading and speech production areas. This study investigates how reading aloud modulates the neuronal interactions between visual recognition and articulatory areas, when both the putamen and thalamus are explicitly included. Using dynamic causal modeling in skilled readers who were reading regularly spelled English words, we compared 27 possible pathways that might connect the ventral anterior occipito-temporal sulcus (aOT) to articulatory areas in the precentral cortex (PrC). We focused on whether the neuronal interactions within these pathways were increased by reading relative to picture naming and other visual and articulatory control conditions. The results provide strong evidence that reading boosts the aOT–PrC pathway via the putamen but not the thalamus. However, the putamen pathway was not exclusive because there was also evidence for another reading pathway that did not involve either the putamen or the thalamus. We conclude that the putamen plays a special role in reading but this is likely to vary with individual reading preferences and strategies

Chimeric protein repair of laminin polymerization ameliorates muscular dystrophy phenotype

Mutations in laminin α2-subunit (Lmα2, encoded by LAMA2) are linked to approximately 30% of congenital muscular dystrophy cases. Mice with a homozygous mutation in Lama2 (dy2J mice) express a nonpolymerizing form of laminin-211 (Lm211) and are a model for ambulatory-type Lmα2-deficient muscular dystrophy. Here, we developed transgenic dy2J mice with muscle-specific expression of αLNNd, a laminin/nidogen chimeric protein that provides a missing polymerization domain. Muscle-specific expression of αLNNd in dy2J mice resulted in strong amelioration of the dystrophic phenotype, manifested by the prevention of fibrosis and restoration of forelimb grip strength. αLNNd also restored myofiber shape, size, and numbers to control levels in dy2J mice. Laminin immunostaining and quantitation of tissue extractions revealed increased Lm211 expression in αLNNd-transgenic dy2J mice. In cultured myotubes, we determined that αLNNd expression increased myotube surface accumulation of polymerization-deficient recombinant laminins, with retention of collagen IV, reiterating the basement membrane (BM) changes observed in vivo. Laminin LN domain mutations linked to several of the Lmα2-deficient muscular dystrophies are predicted to compromise polymerization. The data herein support the hypothesis that engineered expression of αLNNd can overcome polymerization deficits to increase laminin, stabilize BM structure, and substantially ameliorate muscular dystrophy

Getting Under the Skin of Clinical Inertia in Insulin Initiation: The Translating Research Into Action for Diabetes (TRIAD) Insulin Starts Project

Purpose The purpose of this cross-sectional study is to explore primary care providers’ (PCPs) perceptions about barriers to initiating insulin among patients. Studies suggest that many patients with poorly controlled type 2 diabetes do not receive insulin initiation by PCPs. Methods As part of the Translating Research Into Action for Diabetes study, the authors conducted structured interviews in health systems in Indiana, New Jersey, and California, asking PCPs about the importance of insulin initiation and factors affecting this decision. The authors calculated proportions choosing each multiple-choice response option and listed the most frequently offered open-ended response categories. Results Among 83 PCPs, 45% were women; 60% were white; and they averaged 13.4 years in practice. Four-fifths of PCPs endorsed guideline-concordant glycemic targets, but 54% individualized targets based on patient age, life expectancy, medical comorbidities, self-management capacity, and willingness. Most (64%) reported that many patients were resistant to new oral or insulin therapies due to fears about the therapy and what it meant about their disease progression. Two-thirds (64%) cited patient resistance as a barrier to insulin initiation, and 43% cited problems with patient self-management, including cognitive or mental health issues, dexterity, or ability to adhere. Eighty percent felt that patient nonadherence would dissuade them from initiating insulin at least some of the time. Conclusions PCPs perceived that patient resistance and poor self- management skills were significant barriers to initiating insulin. Future studies should investigate whether systems-level interventions to improve patient-provider communication about insulin and enhance providers’ perceptions of patient self-management capacity can increase guideline-concordant, patient-centered insulin initiation

Structural correlates of semantic and phonemic fluency ability in first and second languages

Category and letter fluency tasks are commonly used clinically to investigate the semantic and phonological processes central to speech production, but the neural correlates of these processes are difficult to establish with functional neuroimaging because of the relatively unconstrained nature of the tasks. This study investigated whether differential performance on semantic (category) and phonemic (letter) fluency in neurologically normal participants was reflected in regional gray matter density. The participants were 59 highly proficient speakers of 2 languages. Our findings corroborate the importance of the left inferior temporal cortex in semantic relative to phonemic fluency and show this effect to be the same in a first language (L1) and second language (L2). Additionally, we show that the pre-supplementary motor area (pre-SMA) and head of caudate bilaterally are associated with phonemic more than semantic fluency, and this effect is stronger for L2 than L1 in the caudate nuclei. To further validate these structural results, we reanalyzed previously reported functional data and found that pre-SMA and left caudate activation was higher for phonemic than semantic fluency. On the basis of our findings, we also predict that lesions to the pre-SMA and caudate nuclei may have a greater impact on phonemic than semantic fluency, particularly in L2 speakers

Temporal trends in recording of diabetes on death certificates: results from Translating Research Into Action for Diabetes (TRIAD)

OBJECTIVE: To determine the frequency that diabetes is reported on death certificates of decedents with known diabetes and describe trends in reporting over 8 years. RESEARCH DESIGN AND METHODS: Data were obtained from 11,927 participants with diabetes who were enrolled in Translating Research into Action for Diabetes, a multicenter prospective observational study of diabetes care in managed care. Data on decedents (N=2,261) were obtained from the National Death Index from 1 January 2000 through 31 December 2007. The primary dependent variables were the presence of the ICD-10 codes for diabetes listed anywhere on the death certificate or as the underlying cause of death. RESULTS: Diabetes was recorded on 41% of death certificates and as the underlying cause of death for 13% of decedents with diabetes. Diabetes was significantly more likely to be reported on the death certificate of decedents dying of cardiovascular disease than all other causes. There was a statistically significant trend of increased reporting of diabetes as the underlying cause of death over time (P<0.001), which persisted after controlling for duration of diabetes at death. The increase in reporting of diabetes as the underlying cause of death was associated with a decrease in the reporting of cardiovascular disease as the underlying cause of death (P<0.001). CONCLUSIONS: Death certificates continue to underestimate the prevalence of diabetes among decedents. The increase in reporting of diabetes as the underlying cause of death over the past 8 years will likely impact estimates of the burden of diabetes in the U.S