High-fidelity linear optical quantum computing with polarization encoding

We show that the KLM scheme [Knill, Laflamme and Milburn, Nature {\bf 409}, 46] can be implemented using polarization encoding, thus reducing the number of path modes required by half. One of the main advantages of this new implementation is that it naturally incorporates a loss detection mechanism that makes the probability of a gate introducing a non-detected error, when non-ideal detectors are considered, dependent only on the detector dark-count rate and independent of its efficiency. Since very low dark-count rate detectors are currently available, a high-fidelity gate (probability of error of order $10^{-6}$ conditional on the gate being successful) can be implemented using polarization encoding. The detector efficiency determines the overall success probability of the gate but does not affect its fidelity. This can be applied to the efficient construction of optical cluster states with very high fidelity for quantum computing.Comment: 12 pages, 7 figures. Improved construction of high-fidelity entangled ancilla; references adde

Critical self-organization of astrophysical shocks

There are two distinct regimes of the first order Fermi acceleration at shocks. The first is a linear (test particle) regime in which most of the shock energy goes into thermal and bulk motion of the plasma. The second is an efficient regime when it goes into accelerated particles. Although the transition region between them is narrow, we identify the factors that drive the system to a {\it self-organized critical state} between those two. Using an analytic solution, we determine this critical state and calculate the spectra and maximum energy of accelerated particles.Comment: To appear in ApJL, Sec.3 extensively rewritten, 4 pages, Latex, emulateapj.sty, eps

Development of the L-1011 four-dimensional flight management system

The development of 4-D guidance and control algorithms for the L-1011 Flight Management System is described. Four-D Flight Management is a concept by which an aircraft's flight is optimized along the 3-D path within the constraints of today's ATC environment, while its arrival time is controlled to fit into the air traffic flow without incurring or causing delays. The methods developed herein were designed to be compatible with the time-based en route metering techniques that were recently developed by the Dallas/Fort Worth and Denver Air Route Traffic Control Centers. The ensuing development of the 4-D guidance algorithms, the necessary control laws and the operational procedures are discussed. Results of computer simulation evaluation of the guidance algorithms and control laws are presented, along with a description of the software development procedures utilized

Evidence for an incommensurate magnetic resonance in La(2-x)Sr(x)CuO(4)

We study the effect of a magnetic field (applied along the c-axis) on the low-energy, incommensurate magnetic fluctuations in superconducting La(1.82)Sr(0.18)CuO(4). The incommensurate peaks at 9 meV, which in zero-field were previously shown to sharpen in q on cooling below T_c [T. E. Mason et al., Phys. Rev. Lett. 77, 1604 (1996)], are found to broaden in q when a field of 10 T is applied. The applied field also causes scattered intensity to shift into the spin gap. We point out that the response at 9 meV, though occurring at incommensurate wave vectors, is comparable to the commensurate magnetic resonance observed at higher energies in other cuprate superconductors.Comment: 8 pages, including 4 figure

Oscillating instanton solutions in curved space

We investigate oscillating instanton solutions of a self-gravitating scalar field between degenerate vacua. We show that there exist O(4)-symmetric oscillating solutions in a de Sitter background. The geometry of this solution is finite and preserves the $Z_{2}$ symmetry. The nontrivial solution corresponding to tunneling is possible only if the effect of gravity is taken into account. We present numerical solutions of this instanton, including the phase diagram of solutions in terms of the parameters of the present work and the variation of energy densities. Our solutions can be interpreted as solutions describing an instanton-induced domain wall or braneworld-like object rather than a kink-induced domain wall or braneworld. The oscillating instanton solutions have a thick wall and the solutions can be interpreted as a mechanism providing nucleation of the thick wall for topological inflation. We remark that $Z_{2}$ invariant solutions also exist in a flat and anti-de Sitter background, though the physical significance is not clear.Comment: 25 pages, 11 figues. Some typos corrected, references added, and Ch3. modified according to referee's comment