Quantum Spin Dynamics and Quantum Computation

We describe a simulation method for a quantum spin model of a generic, general purpose quantum computer. The use of this quantum computer simulator is illustrated through several implementations of Grover's database search algorithm. Some preliminary results on the stability of quantum algorithms are presented.Comment: 6 pages, 4 figures ; Minor errors corrected and figures update

SURVEILLANCE OF SELECTED DISEASES IN FREE-RANGING ELK (\u3ci\u3eCERVUS ELAPHUS NELSONI\u3c/i\u3e) IN NEBRASKA, 1995-2009

Sera samples were collected from 21 free-ranging, captured female elk (Cervus elaphus nelsoni) in 1995- 96, and tissue and sera samples were collected from 415 hunter-harvested elk from 1995 to 2006 and tested for selected diseases. Titers for Anaplasma marginale were detected in 81 of 436 (19%) elk. Occurrence of antibodies to anaplasmosis increased from 4 to 40 elk from 2002 to 2006. Titers for bovine viral diarrhea virus (BVDV) were detected in 18 of 346 (5%) samples. Titers for Leptospira interrogans serovars were detected in 21 of 289 (7%) of samples from 1995 to 2004. Titers for bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) were detected in 65 of 370 (18%) sampled elk during 1995-2006. Biologists collected obex tissues from 566 elk from 1997 to 2009 and found evidence of chronic wasting disease (CWO) in one elk in 2009. No brucellosis was detected. Due to the prevalence of several diseases in elk in Nebraska, we recommend that surveillance efforts continue

SURVEILLANCE OF SELECTED DISEASES IN FREE-RANGING ELK (\u3ci\u3eCERVUS ELAPHUS NELSONI\u3c/i\u3e) IN NEBRASKA, 1995-2009

Sera samples were collected from 21 free-ranging, captured female elk (Cervus elaphus nelsoni) in 1995- 96, and tissue and sera samples were collected from 415 hunter-harvested elk from 1995 to 2006 and tested for selected diseases. Titers for Anaplasma marginale were detected in 81 of 436 (19%) elk. Occurrence of antibodies to anaplasmosis increased from 4 to 40 elk from 2002 to 2006. Titers for bovine viral diarrhea virus (BVDV) were detected in 18 of 346 (5%) samples. Titers for Leptospira interrogans serovars were detected in 21 of 289 (7%) of samples from 1995 to 2004. Titers for bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) were detected in 65 of 370 (18%) sampled elk during 1995-2006. Biologists collected obex tissues from 566 elk from 1997 to 2009 and found evidence of chronic wasting disease (CWO) in one elk in 2009. No brucellosis was detected. Due to the prevalence of several diseases in elk in Nebraska, we recommend that surveillance efforts continue

Effects of nonlinear sweep in the Landau-Zener-Stueckelberg effect

We study the Landau-Zener-Stueckelberg (LZS) effect for a two-level system with a time-dependent nonlinear bias field (the sweep function) W(t). Our main concern is to investigate the influence of the nonlinearity of W(t) on the probability P to remain in the initial state. The dimensionless quantity epsilon = pi Delta ^2/(2 hbar v) depends on the coupling Delta of both levels and on the sweep rate v. For fast sweep rates, i.e., epsilon << l and monotonic, analytic sweep functions linearizable in the vicinity of the resonance we find the transition probability 1-P ~= epsilon (1+a), where a>0 is the correction to the LSZ result due to the nonlinearity of the sweep. Further increase of the sweep rate with nonlinearity fixed brings the system into the nonlinear-sweep regime characterized by 1-P ~= epsilon ^gamma with gamma neq 1 depending on the type of sweep function. In case of slow sweep rates, i.e., epsilon >>1 an interesting interference phenomenon occurs. For analytic W(t) the probability P=P_0 e^-eta is determined by the singularities of sqrt{Delta ^2+W^2(t)} in the upper complex plane of t. If W(t) is close to linear, there is only one singularity, that leads to the LZS result P=e^-epsilon with important corrections to the exponent due to nonlinearity. However, for, e.g., W(t) ~ t^3 there is a pair of singularities in the upper complex plane. Interference of their contributions leads to oscillations of the prefactor P_0 that depends on the sweep rate through epsilon and turns to zero at some epsilon. Measurements of the oscillation period and of the exponential factor would allow to determine Delta, independently.Comment: 11 PR pages, 12 figures. To be published in PR

Quantum Nonlinear Switching Model

We present a method, the dynamical cumulant expansion, that allows to calculate quantum corrections for time-dependent quantities of interacting spin systems or single spins with anisotropy. This method is applied to the quantum-spin model \hat{H} = -H_z(t)S_z + V(\bf{S}) with H_z(\pm\infty) = \pm\infty and \Psi (-\infty)=|-S> we study the quantity P(t)=(1-_t/S)/2. The case V(\bf{S})=-H_x S_x corresponds to the standard Landau-Zener-Stueckelberg model of tunneling at avoided-level crossing for N=2S independent particles mapped onto a single-spin-S problem, P(t) being the staying probability. Here the solution does not depend on S and follows, e.g., from the classical Landau-Lifshitz equation. A term -DS_z^2 accounts for particles' interaction and it makes the model nonlinear and essentially quantum mechanical. The 1/S corrections obtained with our method are in a good accord with a full quantum-mechanical solution if the classical motion is regular, as for D>0.Comment: 4 Phys. Rev. pages 2 Fig

Landau-Zener-Stueckelberg effect in a model of interacting tunneling systems

The Landau-Zener-Stueckelberg (LZS) effect in a model system of interacting tunneling particles is studied numerically and analytically. Each of N tunneling particles interacts with each of the others with the same coupling J. This problem maps onto that of the LZS effect for a large spin S=N/2. The mean-field limit N=>\infty corresponds to the classical limit S=>\infty for the effective spin. It is shown that the ferromagnetic coupling J>0 tends to suppress the LZS transitions. For N=>\infty there is a critical value of J above which the staying probability P does not go to zero in the slow sweep limit, unlike the standard LZS effect. In the same limit for J>0 LZS transitions are boosted and P=0 for a set of finite values of the sweep rate. Various limiting cases such as strong and weak interaction, slow and fast sweep are considered analytically. It is shown that the mean-field approach works well for arbitrary N if the interaction J is weak.Comment: 13 PR pages, 15 Fig

Temperature dependence of ESR intensity for the nanoscale molecular magnet V15

The electron spin resonance (ESR) of nanoscale molecular magnet ${\rm V}_{15}$ is studied. Since the Hamiltonian of ${\rm V}_{15}$ has a large Hilbert space and numerical calculations of the ESR signal evaluating the Kubo formula with exact diagonalization method is difficult, we implement the formula with the help of the random vector technique and the Chebyshev polynominal expansion, which we name the double Chebyshev expansion method. We calculate the temperature dependence of the ESR intensity of ${\rm V}_{15}$ and compare it with the data obtained in experiment. As another complementary approach, we also implement the Kubo formula with the subspace iteration method taking only important low-lying states into account. We study the ESR absorption curve below $100{\rm K}$ by means of both methods. We find that side peaks appear due to the Dzyaloshinsky-Moriya interaction and these peaks grows as temperature decreases.Comment: 9 pages, 4 figures. To appear in J. Phys. Soc. Jpn. Supp

Cutting Edge: Suppression of GM-CSF Expression in Murine and Human T Cells by IL-27:suppression of GM-CSF expression in murine and human T cells by IL-27

GM-CSF is a potent pro-inflammatory cytokine that plays a pathogenic role in the CNS inflammatory disease, EAE. As IL-27 ameliorates EAE, we hypothesised that IL-27 suppresses GM-CSF expression by T cells. We found that IL-27 suppressed GM-CSF expression in CD4(+) and CD8(+) T cells in splenocyte and purified T cell cultures. IL-27 suppressed GM-CSF in Th1, but not Th17 cells. IL-27 also suppressed GM-CSF expression by human T cells in non-polarised and Th1 but not Th17 polarised PBMC cultures. In vivo, IL-27p28 deficiency resulted in increased GM-CSF expression by CNS infiltrating T cells during Toxoplasma gondii infection. While in vitro suppression of GM-CSF by IL-27 was independent of IL-2 suppression, IL-10 up-regulation or SOCS3 signalling, we observed that IL-27-driven suppression of GM-CSF was STAT1 dependent. Our findings demonstrate that IL-27 is a robust negative regulator of GM-CSF expression in T cells which likely inhibits T cell pathogenicity in CNS inflammation

Galactic Cosmic Ray Origins and OB Associations: Evidence from SuperTIGER Observations of Elements 26_{26}Fe through 40_{40}Zr

We report abundances of elements from $_{26}$Fe to $_{40}$Zr in the cosmic radiation measured by the SuperTIGER (Trans-Iron Galactic Element Recorder) instrument during 55 days of exposure on a long-duration balloon flight over Antarctica. These observations resolve elemental abundances in this charge range with single-element resolution and good statistics. These results support a model of cosmic-ray origin in which the source material consists of a mixture of 19$^{+11}_{-6}$\% material from massive stars and $\sim$81\% normal interstellar medium (ISM) material with solar system abundances. The results also show a preferential acceleration of refractory elements (found in interstellar dust grains) by a factor of $\sim$4 over volatile elements (found in interstellar gas) ordered by atomic mass (A). Both the refractory and volatile elements show a mass-dependent enhancement with similar slopes.Comment: 9 pages, 12 figures, 2 tables, accepted by Ap