Purification of large bicolorable graph states

We describe novel purification protocols for bicolorable graph states. The protocols scale efficiently for large graph states. We introduce a method of analysis that allows us to derive simple recursion relations characterizing their behavior as well as analytical expressions for their thresholds and fixed point behavior. We introduce two purification protocols with high threshold. They can, for graph degree four, tolerate 1% (3%) gate error or 20% (30%) local error.Comment: 12 pages, 5 figures, revtex; typos and clarifications adde

Casimir forces in the time domain II: Applications

Our preceding paper introduced a method to compute Casimir forces in arbitrary geometries and for arbitrary materials that was based on a finite-difference time-domain (FDTD) scheme. In this manuscript, we focus on the efficient implementation of our method for geometries of practical interest and extend our previous proof-of-concept algorithm in one dimension to problems in two and three dimensions, introducing a number of new optimizations. We consider Casimir piston-like problems with nonmonotonic and monotonic force dependence on sidewall separation, both for previously solved geometries to validate our method and also for new geometries involving magnetic sidewalls and/or cylindrical pistons. We include realistic dielectric materials to calculate the force between suspended silicon waveguides or on a suspended membrane with periodic grooves, also demonstrating the application of PML absorbing boundaries and/or periodic boundaries. In addition we apply this method to a realizable three-dimensional system in which a silica sphere is stably suspended in a fluid above an indented metallic substrate. More generally, the method allows off-the-shelf FDTD software, already supporting a wide variety of materials (including dielectric, magnetic, and even anisotropic materials) and boundary conditions, to be exploited for the Casimir problem.Comment: 11 pages, 12 figures. Includes additional examples (dispersive materials and fully three-dimensional systems

Achieving a Strongly Temperature-Dependent Casimir Effect

We propose a method of achieving large temperature sensitivity in the Casimir force that involves measuring the stable separation between dielectric objects immersed in fluid. We study the Casimir force between slabs and spheres using realistic material models, and find large > 2nm/K variations in their stable separations (hundreds of nanometers) near room temperature. In addition, we analyze the effects of Brownian motion on suspended objects, and show that the average separation is also sensitive to changes in temperature . Finally, this approach also leads to rich qualitative phenomena, such as irreversible transitions, from suspension to stiction, as the temperature is varied

Structural anisotropy and orientation-induced Casimir repulsion in fluids

In this work we theoretically consider the Casimir force between two periodic arrays of nanowires (both in vacuum, and on a substrate separated by a fluid) at separations comparable to the period. Specifically, we compute the dependence of the exact Casimir force between the arrays under both lateral translations and rotations. Although typically the force between such structures is well-characterized by the Proximity Force Approximation (PFA), we find that in the present case the microstructure modulates the force in a way qualitatively inconsistent with PFA. We find instead that effective-medium theory, in which the slabs are treated as homogeneous, anisotropic dielectrics, gives a surprisingly accurate picture of the force, down to separations of half the period. This includes a situation for identical, fluid-separated slabs in which the exact force changes sign with the orientation of the wire arrays, whereas PFA predicts attraction. We discuss the possibility of detecting these effects in experiments, concluding that this effect is strong enough to make detection possible in the near future.Comment: 12 pages, 9, figure. Published version with expanded discussio

Structural anisotropy and orientation-induced Casimir repulsion in fluids

In this work we theoretically consider the Casimir force between two periodic arrays of nanowires (both in vacuum, and on a substrate separated by a fluid) at separations comparable to the period. Specifically, we compute the dependence of the exact Casimir force between the arrays under both lateral translations and rotations. Although typically the force between such structures is well-characterized by the Proximity Force Approximation (PFA), we find that in the present case the microstructure modulates the force in a way qualitatively inconsistent with PFA. We find instead that effective-medium theory, in which the slabs are treated as homogeneous, anisotropic dielectrics, gives a surprisingly accurate picture of the force, down to separations of half the period. This includes a situation for identical, fluid-separated slabs in which the exact force changes sign with the orientation of the wire arrays, whereas PFA predicts attraction. We discuss the possibility of detecting these effects in experiments, concluding that this effect is strong enough to make detection possible in the near future.Comment: 12 pages, 9, figure. Published version with expanded discussio

Evidence for the Gompertz Curve in the Income Distribution of Brazil 1978-2005

This work presents an empirical study of the evolution of the personal income distribution in Brazil. Yearly samples available from 1978 to 2005 were studied and evidence was found that the complementary cumulative distribution of personal income for 99% of the economically less favorable population is well represented by a Gompertz curve of the form $G(x)=\exp [\exp (A-Bx)]$, where $x$ is the normalized individual income. The complementary cumulative distribution of the remaining 1% richest part of the population is well represented by a Pareto power law distribution $P(x)= \beta x^{-\alpha}$. This result means that similarly to other countries, Brazil's income distribution is characterized by a well defined two class system. The parameters $A$, $B$, $\alpha$, $\beta$ were determined by a mixture of boundary conditions, normalization and fitting methods for every year in the time span of this study. Since the Gompertz curve is characteristic of growth models, its presence here suggests that these patterns in income distribution could be a consequence of the growth dynamics of the underlying economic system. In addition, we found out that the percentage share of both the Gompertzian and Paretian components relative to the total income shows an approximate cycling pattern with periods of about 4 years and whose maximum and minimum peaks in each component alternate at about every 2 years. This finding suggests that the growth dynamics of Brazil's economic system might possibly follow a Goodwin-type class model dynamics based on the application of the Lotka-Volterra equation to economic growth and cycle.Comment: 22 pages, 15 figures, 4 tables. LaTeX. Accepted for publication in "The European Physical Journal B

In Situ Calls Of The Marine Perciform Glaucosoma Hebraicum

West Australian dhufish (Glaucosoma hebraicum), a marine perciform, possess a swim bladder which has associated muscles that are used in sound production. Individuals have been recorded producing sounds during capture that may be associated with disturbance from their normal behaviour. To determine whether individuals produce sound during natural behaviour, a passive sea-noise logger was deployed on the seafloor for one month in close proximity to low-relief artificialsubstrates occupied by G. hebraicum. During this time, both juvenile and sub-adult G. hebraicum were observed within metres of the logger on numerous occasions. At approximately the same time, sounds with characteristics similar to the disturbance calls of G. hebraicum were detected by the logger. Two types of swimbladder generated calls were recorded, one of widely-spaced pulses and the other of pulses in quick succession The maximum received levels and sound exposurelevels of the recorded calls were 132 dB re 1 μPa and 121 dB re 1 μPa2.s, respectively. Based on previously determined G. hebraicum source levels and time of arrival techniques (direct and surface-reflected ray paths), the vocalising fish were estimated at between 1 and 19.5 m from the hydrophone and thus within the area where they had been observed. This study has provided evidence that juvenile G. hebraicum produce sounds at similar source levels to those generated during human induced disturbance. This indicates that sound is produced by individuals of this species during normal behaviour, but may or may not be associated with natural sources of disturbance

A Census of Rotating Radio Transients at 150 MHz with the Irish LOFAR Station

Rotating radio transients (RRATs) are neutron stars that emit detectable radio bursts sporadically. They are statistically distinct in the neutron star population, in many observable properties, but by their nature are practically difficult to study in depth. In this paper, we present the results from 1408 h of observations of RRAT candidates using the Irish station of the Low Frequency Array (LOFAR) at 150 MHz. As of October 2022, this census involved observing 113 sources, leading to 29 detections which were then followed up systematically. Single-pulse emission was detected from 25 sources, and periodic emission from 14 sources. 18 sources were found to have emission behaviour that is not discussed in prior works using LOFAR instruments. Four novel or modified source periods have been determined, ranging from 1.5-3.9 s, and 8 new or updated phase-coherent pulsar timing ephemerides have been produced using detected bursts. One unexpected single-pulse with a clearly-Galactic dispersion measure was detected as a part of this work, but has not been re-detected in follow-up observations. Observations are ongoing to expand the number of observed sources and further characterise and improve ephemerides for the detected sources. This census has demonstrated the capability for international LOFAR stations to detect, monitor and characterise a significant fraction of these unique sources.Comment: Accepted by MNRAS. 24 pages, 7 figures, 8 table

Calculation of nonzero-temperature Casimir forces in the time domain

We show how to compute Casimir forces at nonzero temperatures with time-domain electromagnetic simulations, for example using a finite-difference time-domain (FDTD) method. Compared to our previous zero-temperature time-domain method, only a small modification is required, but we explain that some care is required to properly capture the zero-frequency contribution. We validate the method against analytical and numerical frequency-domain calculations, and show a surprising high-temperature disappearance of a non-monotonic behavior previously demonstrated in a piston-like geometry.Comment: 5 pages, 2 figures, submitted to Physical Review A Rapid Communicatio