Quantum Convolutional Error Correcting Codes

I report two general methods to construct quantum convolutional codes for $N$-state quantum systems. Using these general methods, I construct a quantum convolutional code of rate 1/4, which can correct one quantum error for every eight consecutive quantum registers.Comment: Minor revisions and clarifications. To appear in Phys. Rev.

Exclusive Hadronic D Decays to eta' and eta

Hadronic decay modes $D^0\to(\bar K^0, \bar K^{*0})\eta,\eta'$ and $(D^+,D_s^+)\to(\pi^+,\rho^+)\eta,\eta'$ are studied in the generalized factorization approach. Form factors for $(D,D_s^+)\to(\eta,\eta')$ transitions are carefully evaluated by taking into account the wave function normalization of the eta and eta'. The predicted branching ratios are generally in agreement with experiment except for $D^0\to\bar K^0\eta', D^+\to\pi^+\eta$ and $D_s^+\to\rho^+\eta'$; the calculated decay rates for the first two decay modes are too small by an order of magnitude. We show that the weak decays $D^0\to K^-\pi^+$ and $D^+\to K^+\bar K^0$ followed by resonance-induced final-state interactions (FSI), which are amenable technically, are able to enhance the branching ratios of $D^0\to\bar K^0\eta'$ and $D^+\to\pi^+\eta$ dramatically without affecting the agreement between theory and experiment for $D^0\to\bar K^0\eta$ and $D^+\to\pi^+\eta'$. We argue that it is difficult to understand the observed large decay rates of $D_s^+\to \rho^+\eta'$ and $\rho^+\eta$ simultaneously; FSI, W-annihilation and the production of excess eta' from gluons are not helpful in this regard. The large discrepancy between the factorization hypothesis and experiment for the ratio of $D_s^+\to\rho^+ \eta'$ and $D_s^+\to\eta' e^+\nu$ remains as an enigma.Comment: 15 pages, 1 figure, to appear in Phys. Rev. D. Form factors for D to eta and eta' transitions are slightly change

Multiplpe Choice Minority Game With Different Publicly Known Histories

In the standard Minority Game, players use historical minority choices as the sole public information to pick one out of the two alternatives. However, publishing historical minority choices is not the only way to present global system information to players when more than two alternatives are available. Thus, it is instructive to study the dynamics and cooperative behaviors of this extended game as a function of the global information provided. We numerically find that although the system dynamics depends on the kind of public information given to the players, the degree of cooperation follows the same trend as that of the standard Minority Game. We also explain most of our findings by the crowd-anticrowd theory.Comment: Extensively revised, to appear in New J Phys, 7 pages with 4 figure

Factorial Moments in a Generalized Lattice Gas Model

We construct a simple multicomponent lattice gas model in one dimension in which each site can either be empty or occupied by at most one particle of any one of $D$ species. Particles interact with a nearest neighbor interaction which depends on the species involved. This model is capable of reproducing the relations between factorial moments observed in high--energy scattering experiments for moderate values of $D$. The factorial moments of the negative binomial distribution can be obtained exactly in the limit as $D$ becomes large, and two suitable prescriptions involving randomly drawn nearest neighbor interactions are given. These results indicate the need for considerable care in any attempt to extract information regarding possible critical phenomena from empirical factorial moments.Comment: 15 pages + 1 figure (appended as postscript file), REVTEX 3.0, NORDITA preprint 93/4

Flavor SU(3) symmetry and QCD factorization in B→PPB \to PP and PVPV decays

Using flavor SU(3) symmetry, we perform a model-independent analysis of charmless $\bar B_{u,d} (\bar B_s) \to PP, ~PV$ decays. All the relevant topological diagrams, including the presumably subleading diagrams, such as the QCD- and EW-penguin exchange diagrams and flavor-singlet weak annihilation ones, are introduced. Indeed, the QCD-penguin exchange diagram turns out to be important in understanding the data for penguin-dominated decay modes. In this work we make efforts to bridge the (model-independent but less quantitative) topological diagram or flavor SU(3) approach and the (quantitative but somewhat model-dependent) QCD factorization (QCDF) approach in these decays, by explicitly showing how to translate each flavor SU(3) amplitude into the corresponding terms in the QCDF framework. After estimating each flavor SU(3) amplitude numerically using QCDF, we discuss various physical consequences, including SU(3) breaking effects and some useful SU(3) relations among decay amplitudes of $\bar B_s \to PV$ and $\bar B_d \to PV$.Comment: 47 pages, 3 figures, 28 table

Designing avionics for lasers & optoelectronics

Unlike imagery-based Earth observation (EO) which has become very widely and cheaply available, gravity sensing EO has not yet emerged from its fundamental science roots. The challenge therefore is to develop gravity sensing instruments that can replicate the success of widespread imagery based EO. There are three main gravity sensing mechanisms under investigation: laser ranging (e.g., GRACE-FO [1]); atom interferometers, which measure gravitation perturbations to the wavefunctions of individual atoms; and ‘relativistic geodesy’ which uses atomic clocks to measure the gravitational curvature of spacetime. All three of these measurement systems use stabilised lasers as their main enabling technology. However traditional laboratory laser systems struggle to meet the robustness, reliability, or low size, weight, and power (SWaP) requirements for use in space. A demonstrator was build that adapted telecommunications industry COTS components, and software radio FPGA/DSP techniques, to develop a new all-fibre space-qualified stabilised laser systems for geodesy that have equivalent performance to laboratory systems. This instrument was used to develop a 780 nm laser system that is stabilised to the Rubidium D2 line - the stabilised laser most commonly required by the quantum and atomic sensing field achieving sufficiently high laser performance for the laser system to be immediately useful for quantum applications (stability: 1-10 kHz, accuracy: 1 MHz); and in an ultra-compact package that has the potential to be used in space (1 litre, 0.5 kg, 10 W) [2]. This paper reports on the current student work that advances the instrument further towards a flight payload – and key avionics design considerations for future researchers. This takes lessons learnt from the ESA ESEO software radio payload in utilising ECSS design practices [3] to fabricate a robust and modular avionics back-end board that can operate with numerous front-end laser or opto-electronics configurations for different quantum applications. The new board consists of a single PCB containing circuitry for TT&C reporting of power supply and voltage conditioning, the current and temperature electronics needed to control a diode laser on orbit, interfaces for photo detectors and opto-electronics, and a high-speed analogue- to-digital conversion network centred around a FPGA. As an example, digital signal processing performed frequency-modulated spectroscopy on a warm Rubidium vapour using an all-fibre optical arrangement

Prevalence of Exposure to Complex Trauma and Community Violence and Their Associations With Internalizing and Externalizing Symptoms

Studies about trauma often tend to focus on abuse and neglect. However important, these studies may neglect the importance of the broader community context that is often associated with trauma, and complex trauma (CT) in particular. This study aimed to investigate the effects of CT (defined in terms of experiencing abuse and/or neglect occurring in the context of relationships with caregivers), and of broader environmental adversity (i.e., exposure to community violence), in a sample of adolescents ( N = 218) from a severely disadvantaged district of Lima, Peru. The study had two aims: (a) to assess the prevalence of CT and its associations with internalizing and externalizing symptoms in these adolescents and (b) to investigate the associations between community violence and both internalizing and externalizing symptoms over and above the effects of CT. In total, 39.4% of the adolescents reported at least one type of moderate to severe trauma. There was a clear association between CT and both internalizing and externalizing symptoms. Ordinal logistic regressions showed that children who were exposed to one or more traumatic experiences were more likely to score within a higher range of internalizing and externalizing symptoms than children with no history of trauma. Finally, exposure to community violence was an important predictor of symptomatology beyond the effects of CT

The environmental performance of protecting seedlings with plastic tree shelters for afforestation in temperate oceanic regions: A UK case study

Restoration of forested land represents an effective strategy to achieve net-zero target emissions by enhancing the removal of greenhouse gases from the atmosphere. The most common afforestation strategy envisages planting seedlings, which are germinated and grown to the desired age at tree nurseries, with plastic shelters to increase growth and survival of trees. This article presents a comprehensive Life Cycle Assessment (LCA) study that compares the environmental performance of current and prospective scenarios for shelter-aided seedling planting compared with a base case where shelters are not employed. The study focuses on the UK, but results and conclusions are valid for other temperate oceanic regions. The scenarios investigated are a combination of different shelters materials and end-of-life (EoL) strategies. Our analysis demonstrates that (i) planting seedling without shelters is the most preferable option across most environmental impact categories (including Climate Change), and in terms of weighted results, (ii) polypropylene shelters are preferable to bio-based alternatives, including polylactic acid-starch blends and bio-polypropylene, (iii) recycling is the most environmentally advantageous EoL treatment. Our study also showed that that the carbon emissions of the scenarios investigated are negligible when compared to the amount of carbon sequestered by a tree in 25 years

A Cellular Automaton Model for Diffusive and Dissipative Systems

We study a cellular automaton model, which allows diffusion of energy (or equivalently any other physical quantities such as mass of a particular compound) at every lattice site after each timestep. Unit amount of energy is randomly added onto a site. Whenever the local energy content of a site reaches a fixed threshold $E_{c1}$, energy will be dissipated. Dissipation of energy propagates to the neighboring sites provided that the energy contents of those sites are greater than or equal to another fixed threshold $E_{c2} (\leq E_{c1})$. Under such dynamics, the system evolves into three different types of states depending on the values of $E_{c1}$ and $E_{c2}$ as reflected in their dissipation size distributions, namely: localized peaks, power laws, or exponential laws. This model is able to describe the behaviors of various physical systems including the statistics of burst sizes and burst rates in type-I X-ray bursters. Comparisons between our model and the famous forest-fire model (FFM) are made.Comment: in REVTEX 3.0. Figures available on request. Extensively revised. Accepted by Phys.Rev.

Unitary designs and codes

A unitary design is a collection of unitary matrices that approximate the entire unitary group, much like a spherical design approximates the entire unit sphere. In this paper, we use irreducible representations of the unitary group to find a general lower bound on the size of a unitary t-design in U(d), for any d and t. We also introduce the notion of a unitary code - a subset of U(d) in which the trace inner product of any pair of matrices is restricted to only a small number of distinct values - and give an upper bound for the size of a code of degree s in U(d) for any d and s. These bounds can be strengthened when the particular inner product values that occur in the code or design are known. Finally, we describe some constructions of designs: we give an upper bound on the size of the smallest weighted unitary t-design in U(d), and we catalogue some t-designs that arise from finite groups.Comment: 25 pages, no figure