Undoing measurement-induced dephasing in circuit QED

We analyze the backaction of homodyne detection and photodetection on superconducting qubits in circuit quantum electrodynamics. Although both measurement schemes give rise to backaction in the form of stochastic phase rotations, which leads to dephasing, we show that this can be perfectly undone provided that the measurement signal is fully accounted for. This result improves upon that of Phys. Rev. A, 82, 012329 (2010), showing that the method suggested can be made to realize a perfect two-qubit parity measurement. We propose a benchmarking experiment on a single qubit to demonstrate the method using homodyne detection. By analyzing the limited measurement efficiency of the detector and bandwidth of the amplifier, we show that the parameter values necessary to see the effect are within the limits of existing technology

Odin observations of ammonia in the Sgr A +50 km/s Cloud and Circumnuclear Disk

Context. The Odin satellite is now into its sixteenth year of operation, much surpassing its design life of two years. One of the sources which Odin has observed in great detail is the Sgr A Complex in the centre of the Milky Way. Aims. To study the presence of NH3 in the Galactic Centre and spiral arms. Methods. Recently, Odin has made complementary observations of the 572 GHz NH3 line towards the Sgr A +50 km/s Cloud and Circumnuclear Disk (CND). Results. Significant NH3 emission has been observed in both the +50 km/s Cloud and the CND. Clear NH3 absorption has also been detected in many of the spiral arm features along the line of sight from the Sun to the core of our Galaxy. Conclusions. The very large velocity width (80 km/s) of the NH3 emission associated with the shock region in the southwestern part of the CND may suggest a formation/desorption scenario similar to that of gas-phase H2O in shocks/outflows.Comment: 5 pages, 3 figures, 3 table

Contrasting fishing effort reduction and habitat connectivity as management strategies to promote alewife (\u3cem\u3eAlosa pseudoharengus\u3c/em\u3e) recovery using an ecosystem model

Small pelagics, or forage fish, link lower and higher trophic levels in marine food webs. Recently, attention has been given to the management of forage fish, including anadromous river herring (Alewife Alosa pseudoharengus, blueback herring A. aestivalis) and American shad (A. sapidissima) due to their current depleted status and historically important ecological and economic roles. Little is known about the impact of changes in their biomass on marine food webs and what management practices will promote their recovery. Estimated historical riverine productivity was utilized to evaluate potential ecosystem impacts of the increasing river to ocean connectivity to resemble 19th-century conditions. The Ecopath with Ecosim modeling framework was used to simulate management strategies, focused on anadromous forage fish, by creating scenarios of fisheries reduction (mixed fishery effort reduction) and river to ocean habitat connectivity (75% of historical connectivity achieved). Sixty-year simulations covered the entire time series including a 36-year forecast period to evaluate the ecosystem impacts of management strategies. Results suggest nonlinear relationships and large changes in biomass flows from forage fish to upper trophic levels in the Gulf of Maine ecosystem. Increases in biomass were observed for pelagic sharks, demersal piscivores, and species of conservation concern such as pinnipeds and seabirds, although overall results were strongly influenced by indirect trophic effects. Promoting anadromous forage fish recovery through increased connectivity resulted in the redundancy of marine ecosystem niches that would increase resilience to climate, fisheries, and other perturbations. This study highlights the value of employing ecosystem models for testing management scenarios to contrast different approaches to recover anadromous forage fish towards its former ecological prominence

Oscillating bound states for a giant atom

We investigate the relaxation dynamics of a single artificial atom interacting, via multiple coupling points, with a continuum of bosonic modes (photons or phonons) in a one-dimensional waveguide. In the non-Markovian regime, where the traveling time of a photon or phonon between the coupling points is sufficiently large compared to the inverse of the bare relaxation rate of the atom, we find that a boson can be trapped and form a stable bound state. As a key discovery, we further find that a persistently oscillating bound state can appear inside the continuous spectrum of the waveguide if the number of coupling points is more than two since such a setup enables multiple bound modes to coexist. This opens up prospects for storing and manipulating quantum information in larger Hilbert spaces than available in previously known bound states

Herschel and Odin observations of H2O, CO, CH, CH+, and NII in the barred spiral galaxy NGC 1365. Bar-induced activity in the outer and inner circumnuclear tori

The Odin satellite is now into its twentieth year of operation, much surpassing its design life of two years. One of its major pursuits was the search for and study of H2O in the Solar System and the Milky Way galaxy. Herschel has observed the central region of NGC 1365 in two positions, and both its SPIRE and PACS observations are available in the Herschel Science Archive. Herschel PACS images have been produced of the 70 and 160 micron infrared emission from the whole galaxy, and also of the cold dust distribution as obtained from the ratio of the 160 to 70 micron images. The Herschel SPIRE observations have been used to produce maps of the 557 GHz o-H2O, 752 GHz p-H2O, 691 GHz CO(6-5), 1037 GHz CO(9-8), 537 GHz CH, 835 GHz CH+, and the 1461 GHz NII lines; however, these observations have no effective velocity resolution. Odin has recently observed the 557 GHz o-H2O ground state line in the central region with high (5 km/s) spectral resolution. The emission and absorption of H2O at 557 GHz, with a velocity resolution of 5 km/s, has been marginally detected in NGC 1365 with Odin. The H2O is predominantly located in a shocked 15" (1.3 kpc) region near some central compact radio sources and hot-spot HII regions, close to the northeast component of the molecular torus surrounding the nucleus. An analysis of the H2O line intensities and velocities indicates that a shock-region is located here. This is corroborated by a statistical image deconvolution of our SEST CO(3-2) observations, yielding 5" resolution, and a study of our VLA HI absorption observations. Additionally, an enticing 20" HI ridge is found to extend south-southeast from the nucleus, coinciding in position with the southern edge of an OIII outflow cone, emanating from the nucleus. The molecular chemistry of the shocked central region is analyzed with special emphasis on the CO, H2O and CH, CH+ results.Comment: 25 pages, 11 figure

Semiclassical Time Evolution and Trace Formula for Relativistic Spin-1/2 Particles

We investigate the Dirac equation in the semiclassical limit \hbar --> 0. A semiclassical propagator and a trace formula are derived and are shown to be determined by the classical orbits of a relativistic point particle. In addition, two phase factors enter, one of which can be calculated from the Thomas precession of a classical spin transported along the particle orbits. For the second factor we provide an interpretation in terms of dynamical and geometric phases.Comment: 8 pages, no figure

THE ROLE OF SHOE SOLE DUROMETER ON JUMPING KINETICS

This study investigated the relationship between shoe heel density (HD), toe density (TD) and the peak ground reaction force (GRF) and rate of force development (RFD) during jumping. This study also assessed the reliability of the durometer to assess shoe soles. Subjects included 12 men. Shoe HD and TD were assessed via durometer and kinetics were determined during the countermovement jump on a force platform. A Pearson bivariate correlation analysis was performed. Results reveal that HD was not correlated with GRF (r = -.22, p = .50) or RFD (r = -.14, p = .67). Similarly, TD was not correlated with GRF (r = -.29, p = .37) or RFD (r = -.28, p = .37). Intraclass correlation coefficients for the heel and toe durometer were .95 and .92, respectively. Jumping kinetics were not mediated by shoe sole characteristics, though the durometer was reliable for assessing shoe soles

Low-frequency broadband sound source localization using an adaptive normal mode back-propagation approach in a shallow-water ocean

Author Posting. © Acoustical Society of America, 2012. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 131 (2012): 1798-1813, doi:10.1121/1.3672643.A variety of localization methods with normal mode theory have been established for localizing low frequency (below a few hundred Hz), broadband signals in a shallow water environment. Gauss-Markov inverse theory is employed in this paper to derive an adaptive normal mode back-propagation approach. Joining with the maximum a posteriori mode filter, this approach is capable of separating signals from noisy data so that the back-propagation will not have significant influence from the noise. Numerical simulations are presented to demonstrate the robustness and accuracy of the approach, along with comparisons to other methods. Applications to real data collected at the edge of the continental shelf off New Jersey, USA are presented, and the effects of water column fluctuations caused by nonlinear internal waves and shelfbreak front variability are discussed.The SW06 experiment was supported by the Office of Naval Research