Entangling characterization of (SWAP)1/m and Controlled unitary gates

We study the entangling power and perfect entangler nature of (SWAP)1/m, for m>=1, and controlled unitary (CU) gates. It is shown that (SWAP)1/2 is the only perfect entangler in the family. On the other hand, a subset of CU which is locally equivalent to CNOT is identified. It is shown that the subset, which is a perfect entangler, must necessarily possess the maximum entangling power.Comment: 12 pages, 1 figure, One more paragraph added in Introductio

Detection of Asynchronous Message Passing Errors Using Static Analysis

Concurrent programming is hard and prone to subtle errors. In this paper we present a static analysis that is able to detect some commonly occurring kinds of message passing errors in languages with dynamic process creation and communication based on asynchronous message passing. Our analysis is completely automatic, fast, and strikes a proper balance between soundness and completeness: it is effective in detecting errors and avoids false alarms by computing a close approximation of the interprocess communication topology of programs. We have integrated our analysis in dialyzer, a widely used tool for detecting software defects in Erlang programs, and demonstrate its effectiveness on libraries and applications of considerable size. Despite the fact that these applications have been developed over a long period of time and are reasonably well-tested, our analysis has managed to detect a significant number of previously unknown message passing errors in their code

Generalized Limits for Parameter Sensitivity via Quantum Ziv-Zakai Bound

We study the generalized limit for parameter sensitivity in quantum estimation theory considering the effects of repeated and adaptive measurements. Based on the quantum Ziv-Zakai bound, we derive some lower bounds for parameter sensitivity when the Hamiltonian of system is unbounded and when the adaptive measurements are implemented on the system. We also prove that the parameter sensitivity is bounded by the limit of the minimum detectable parameter. In particular, we examine several known states in quantum phase estimation with non-interacting photons, and show that they can not perform better than Heisenberg limit in a much simpler way with our result.Comment: 8pages, 5 figure

Age of the Peach Springs Tuff, Southeastern California and Western Arizona

Sanidine separates from pumice of the early Miocene Peach Springs Tuff are concordantly dated at 18.5 ± 0.2 Ma by two isotopic techniques. The Peach Springs Tuff is the only known unit that can be correlated between isolated outcrops of Miocene strata from the central Mojave Desert of southeastern California to the western Colorado Plateau in Arizona, across five structural provinces, a distance of 350 km. Thus the age of the Peach Springs Tuff is important to structural and paleogeographic reconstructions of a large region. Biotite and sanidine separates from bulk samples of the Peach Springs Tuff from zones of welding and vapor-phase alteration have not produced consistent ages by the K-Ar method. Published ages of mineral separates from 17 localities ranged from 16.2 to 20.5 Ma. Discordant 40Ar/39Ar incremental release spectra were obtained for one biotite and two of the sanidine separates. Ages that correspond to the last gas increments are as old as 27 Ma. The 40Ar/39Ar incremental release determinations on sanidine separated from blocks of Peach Springs Tuff pumice yield ages of 18.3 ± 0.3 and 18.6 ± 0.4 Ma. Laser fusion measurements yield a mean age of 18.51 ± 0.10. The results suggest that sanidine and biotite K-Ar ages older than about 18.5 Ma are due to inherited Ar from pre-Tertiary contaminants, which likely were incorporated into the tuff during deposition. Sanidine K-Ar ages younger than 18 Ma probably indicate incomplete extraction of radiogenic 40Ar, whereas laser fusion dates of biotite and hornblende younger than 18 Ma likely are due to postdepositional alteration. Laser fusion ages as high as 19.01 Ma on biotite grains from pumice suggest that minerals from pre-Tertiary country rocks also were incorporated in the magma chamber

Positional Disorder, Spin-Orbit Coupling and Frustration in GaMnAs

We study the magnetic properties of metallic GaMnAs. We calculate the effective RKKY interaction between Mn spins using several realistic models for the valence band structure of GaAs. We also study the effect of positional disorder of the Mn on the magnetic properties. We find that the interaction between two Mn spins is anisotropic due to spin-orbit coupling within both the so-called spherical approximation and in the more realistic six band model. The spherical approximation strongly overestimates this anistropy, especially for short distances between Mn ions. Using the obtained effective Hamiltonian we carry out Monte Carlo simulations of finite and zero temperature magnetization and find that, due to orientational frustration of the spins, non-collinear states appear in both valence band approximations for disordered, uncorrelated Mn impurities in the small concentration regime. Introducing correlations among the substitutional Mn positions or increasing the Mn concentration leads to an increase in the remnant magnetization at zero temperature and an almost fully polarized ferromagnetic state.Comment: 17 Pages, 13 Figure

Disorder, spin-orbit, and interaction effects in dilute Ga1−xMnxAs{\rm Ga}_{1-x}{\rm Mn}_x{\rm As}

We derive an effective Hamiltonian for ${\rm Ga}_{1-x}{\rm Mn}_x {\rm As}$ in the dilute limit, where ${\rm Ga}_{1-x}{\rm Mn}_x {\rm As}$ can be described in terms of spin $F=3/2$ polarons hopping between the {\rm Mn} sites and coupled to the local {\rm Mn} spins. We determine the parameters of our model from microscopic calculations using both a variational method and an exact diagonalization within the so-called spherical approximation. Our approach treats the extremely large Coulomb interaction in a non-perturbative way, and captures the effects of strong spin-orbit coupling and Mn positional disorder. We study the effective Hamiltonian in a mean field and variational calculation, including the effects of interactions between the holes at both zero and finite temperature. We study the resulting magnetic properties, such as the magnetization and spin disorder manifest in the generically non-collinear magnetic state. We find a well formed impurity band fairly well separated from the valence band up to $x_{\rm active} \lesssim 0.015$ for which finite size scaling studies of the participation ratios indicate a localization transition, even in the presence of strong on-site interactions, where $x_{\rm active}<x_{\rm nom}$ is the fraction of magnetically active Mn. We study the localization transition as a function of hole concentration, Mn positional disorder, and interaction strength between the holes.Comment: 15 pages, 12 figure

Entanglement Evolution in the Presence of Decoherence

The entanglement of two qubits, each defined as an effective two-level, spin 1/2 system, is investigated for the case that the qubits interact via a Heisenberg XY interaction and are subject to decoherence due to population relaxation and thermal effects. For zero temperature, the time dependent concurrence is studied analytically and numerically for some typical initial states, including a separable (unentangled) initial state. An analytical formula for non-zero steady state concurrence is found for any initial state, and optimal parameter values for maximizing steady state concurrence are given. The steady state concurrence is found analytically to remain non-zero for low, finite temperatures. We also identify the contributions of global and local coherence to the steady state entanglement.Comment: 12 pages, 4 figures. The second version of this paper has been significantly expanded in response to referee comments. The revised manuscript has been accepted for publication in Journal of Physics

Preanalytical processing of archaeological mammal enamel apatite carbonates for stable isotope investigations: a comparative analysis of the effect of acid treatment on samples from Northwest Australia

Stable isotopic analysis of palaeontological and archaeological biogenic apatite carbonates from herbivorous mammalian species represents an important tool for worldwide palaeoecological research. Tooth enamel carbonates are more resistant to taphonomic processes than bone or dentine carbonates but are not invulnerable to diagenesis. As such, they require careful preanalytical processing that considers depositional environment and age. An established part of this process includes a weak acid treatment to remove soluble exogenous carbonates; however, published treatment times for isotopic studies of archaeological tooth enamel are variable and range from 15\ua0min to over 8\ua0hr. This study tests three different pretreatment protocols on modern and Pleistocene age archaeological kangaroo teeth (dating from contemporary to 46,000 bp) to assess the effect of acid treatment time on isotopic integrity. The results indicate that treatment time is a critical parameter for producing consistency across results and shorter pretreatments of 4\ua0hr or less are preferable for removing diagenetic carbonates while minimising alteration of the biological signal

High-fidelity simulations of CdTe vapor deposition from a new bond-order potential-based molecular dynamics method

CdTe has been a special semiconductor for constructing the lowest-cost solar cells and the CdTe-based Cd1-xZnxTe alloy has been the leading semiconductor for radiation detection applications. The performance currently achieved for the materials, however, is still far below the theoretical expectations. This is because the property-limiting nanoscale defects that are easily formed during the growth of CdTe crystals are difficult to explore in experiments. Here we demonstrate the capability of a bond order potential-based molecular dynamics method for predicting the crystalline growth of CdTe films during vapor deposition simulations. Such a method may begin to enable defects generated during vapor deposition of CdTe crystals to be accurately explored