Resident and transient coyotes exhibit differential patterns of movement behavior across heterogeneous landscapes in the southeastern United States

Coyotes (Canis latrans) are a highly adaptable canid species whose behavioral plasticity has allowed them to persist in a wide array of habitats throughout North America. As generalists, coyotes can alter movement patterns and change territorial strategies between residency (high site fidelity) and transiency (low site fidelity) to maximize fitness. Uncertainty remains about resident and transient coyote movement patterns and habitat use because research has reached conflicting conclusions regarding patterns of habitat use by both groups. We quantified effects of habitat on resident and transient coyote movement behavior using first passage time (FPT) analysis, which assesses recursive movement along an individual's movement path to delineate where they exhibit area‐restricted search (ARS) behaviors relative to habitat attributes. We quantified monthly movement rates for 171 coyotes (76 residents and 53 transients) and then used estimated FPT values in generalized linear mixed models to quantify monthly habitat use for resident and transient coyotes. Transients had greater movement rates than residents across all months except January. Resident FPT values were positively correlated with agricultural land cover during fall and winter, but negatively correlated with agriculture during spring. Resident FPT values were also negatively correlated with developed habitats during May–August, deciduous land cover during June–August, and wetlands during September–January except November. FPT values of transient coyotes were positively correlated with developed areas throughout much of the year and near wetlands during July–September. Transient FPT values were negatively correlated with agriculture during all months except June and July. High FPT values (ARS behavior) of residents and transients were generally correlated with greater densities of edge habitat. Although we observed high individual variation in space use, our study found substantive differences in habitat use between residents and transients, providing further evidence that complexity and plasticity of coyote habitat use is influenced by territorial strategy.

Isotope analysis reveals dietary overlap among sympatric canids

When colonizing new regions, invading species might compete strongly with phylogenetically related species native to the regions they are colonizing, eventually leading to coexistence or displacement. In the southeast of the United States, recently established coyotes (Canis latrans) compete with red fox (Vulpes vulpes) and gray fox (Urocyon cinereoargenteus), although it remains unclear if competition is leading to resource partitioning or displacement by species. Using nitrogen and carbon stable isotopes, we tested the hypothesis that coyotes compete with foxes for food resources, with canids partitioning those resources to mitigate competition. We compared diets of canids in the southeast to those in the Plains region of the United States, a region where all three species historically have coexisted. We analyzed 217 hair samples from both regions pre-1960, prior to coyote colonization of the southeast, and post-2000, after coyotes were ubiquitous there, to assess differences in diet among species for both regions (southeast versus Plains and time periods, pre- versus postcolonization by coyotes). Modeling revealed significant dietary overlap among historical and contemporary populations in the southeast. Historically, all species partitioned resources in the Plains. Contemporarily, red fox and coyotes co-occurring in the Plains overlapped in diet; however, gray fox diet did not overlap with those of red fox and coyotes. Absence of partitioning in diet among co-occurring canids in the southeast indicates that interspecific competition could be strong in the region. Competition among canid populations in the southeast could lead to further resource partitioning among species that promotes coexistence or competitive exclusion of smaller fox species where coyote populations are abundant.

GPS-coupled contaminant monitors on free-ranging Chernobyl wolves challenge a fundamental assumption in exposure assessments

Measurements of external contaminant exposures on individual wildlife are rare because of difficulties in using contaminant monitors on free-ranging animals. Most wildlife contaminant exposure data are therefore simulated with computer models. Rarely are empirical exposure data available to verify model simulations, or to test fundamental assumptions inherent in exposure assessments. We used GPS-coupled contaminant monitors to quantify external exposures to individual wolves (Canis lupus) living within the Belarus portion of Chernobyl's 30-km exclusion zone. The study provided data on animal location and contaminant exposure every 35 min for 6 months, resulting in ~6600 individual locations and ¹³⁷Cs external exposure readings per wolf, representing the most robust external exposure data published to date on free ranging animals. The data provided information on variation in external exposure for each animal over time, as well as variation in external exposure among the eight wolves across the landscape of Chernobyl. The exposure data were then used to test a fundamental assumption in screening-level risk assessments, espoused in guidance documents of the U.S. Environmental Protection Agency and U.S. Department of Energy, - Mean contaminant concentrations conservatively estimate individual external exposures. We tested this assumption by comparing our empirical data to a series of simulations using the ERICA modeling tool. We found that modeled simulations of mean external exposure (10.5 mGy y^-1), based on various measures of central tendency, under-predicted mean exposures measured on five of the eight wolves wearing GPS-contaminant monitors (i.e., 12.3, 26.3, 28.0, 28.8 and 35.7 mGy y^-1). If under-prediction of exposure occurs for some animals, then arguably the use of averaged contaminant concentrations to predict external exposure is not as conservative as proposed by current risk assessment guidance. Thus, a risk assessor's interpretation of simulated exposures in a screening-level risk analysis might be misguided if contaminant concentrations are based on measures of central tendency. We offer three suggestions for risk assessors to consider in order to reduce the probability of underestimating exposure in a screening-level risk assessment.

Occupancy and abundance of free-roaming cats in a fragmented agricultural ecosystem

Context Free-roaming domestic cats are a widespread invasive species, occurring throughout the globe in urban and rural environments alike. However, robust estimates of cat occupancy and abundance, especially in rural, agricultural landscapes, are largely unknown. Aims To estimate cat occupancy and abundance within forested habitat in a fragmented agricultural region of Indiana, USA. Methods Free-roaming cats in 55 forest patches were captured from 2004 to 2010 to assess the effects of landscape attributes on cat occupancy probabilities. During 2009–10 abundance of cats in each habitat patch was estimated based on natural markings of captured individuals. Key results Across the entire study (2004–10) cats in 50 of the 55 patches were detected, but detections varied temporally and spatially. Average occupancy probability was estimated at Ψ = 0.773 (s.e. = 0.109), and detection probability was estimated as P = 0.204 (s.e. = 0.012). Distance to human structures and forest patch isolation both were found to negatively influence cat occupancy. In total, 57 individual cats were captured in 2009 and 55 in 2010, when unique individuals were distinguished. Across all forest patches, average cat abundance was n = 1.08 in 2009 and n = 0.91 in 2010, ranging from 0 to 7 among sampled patches. Conclusions Overall, the distribution of free-roaming cats across a rural agricultural landscape varied temporally and was associated with proximity to human structures and the proximity of other forest habitat. Similarly, abundance was found to vary spatially and temporally. Implications The findings suggest free-roaming cats are widespread throughout agricultural ecosystems, but their distribution is dynamic and non-random. Additionally, the potential for cats to impact native fauna inhabiting remnant forest patches is high in fragmented agricultural ecosystems due to the concentration of native species utilising these patches. Further research is needed to determine the effects free-roaming cats are having on native species in human-dominated, rural ecosystems, and what conservation measures might be implemented to best mitigate any impacts.

Resilient Entangling Gates for Trapped Ions

Constructing a large-scale ion trap quantum processor will require entangling gate operations that are robust in the presence of noise and experimental imperfection. We experimentally demonstrate how a new type of Mølmer-Sørensen gate protects against infidelity caused by heating of the motional mode used during the gate. Furthermore, we show how the same technique simultaneously provides significant protection against slow fluctuations and mis-sets in the secular frequency. Since this parameter sensitivity is worsened in cases where the ions are not ground-state cooled, our method provides a path towards relaxing ion cooling requirements in practical realizations of quantum computing and simulation.

Trapped-Ion Quantum Logic with Global Radiation Fields

Trapped ions are a promising tool for building a large-scale quantum computer. However, the number of required radiation fields for the realization of quantum gates in any proposed ion-based architecture scales with the number of ions within the quantum computer, posing a major obstacle when imagining a device with millions of ions. Here, we present a fundamentally different approach for trapped-ion quantum computing where this detrimental scaling vanishes. The method is based on individually controlled voltages applied to each logic gate location to facilitate the actual gate operation analogous to a traditional transistor architecture within a classical computer processor. To demonstrate the key principle of this approach we implement a versatile quantum gate method based on long-wavelength radiation and use this method to generate a maximally entangled state of two quantum engineered clock qubits with fidelity 0.985(12). This quantum gate also constitutes a simple-to-implement tool for quantum metrology, sensing, and simulation.

Hybrid quantum logic and a test of Bell's inequality using two different atomic isotopes

Entanglement is one of the most fundamental properties of quantum mechanics, and is the key resource for quantum information processing (QIP). Bipartite entangled states of identical particles have been generated and studied in several experiments, and post-selected or heralded entangled states involving pairs of photons, single photons and single atoms, or different nuclei in the solid state, have also been produced. Here we use a deterministic quantum logic gate to generate a 'hybrid' entangled state of two trapped-ion qubits held in different isotopes of calcium, perform full tomography of the state produced, and make a test of Bell's inequality with non-identical atoms. We use a laser-driven two-qubit gate, whose mechanism is insensitive to the qubits' energy splittings, to produce a maximally entangled state of one (40)Ca(+) qubit and one (43)Ca(+) qubit, held 3.5 micrometres apart in the same ion trap, with 99.8 ± 0.6 per cent fidelity. We test the CHSH (Clauser-Horne-Shimony-Holt) version of Bell's inequality for this novel entangled state and find that it is violated by 15 standard deviations; in this test, we close the detection loophole but not the locality loophole. Mixed-species quantum logic is a powerful technique for the construction of a quantum computer based on trapped ions, as it allows protection of memory qubits while other qubits undergo logic operations or are used as photonic interfaces to other processing units. The entangling gate mechanism used here can also be applied to qubits stored in different atomic elements; this would allow both memory and logic gate errors caused by photon scattering to be reduced below the levels required for fault-tolerant quantum error correction, which is an essential prerequisite for general-purpose quantum computing.

Ground-State Cooling of a Trapped Ion Using Long-Wavelength Radiation

We demonstrate ground-state cooling of a trapped ion using radio-frequency (rf) radiation. This is a powerful tool for the implementation of quantum operations, where rf or microwave radiation instead of lasers is used for motional quantum state engineering. We measure a mean phonon number of n[over ¯]=0.13(4) after sideband cooling, corresponding to a ground-state occupation probability of 88(7)%. After preparing in the vibrational ground state, we demonstrate motional state engineering by driving Rabi oscillations between the |n=0⟩ and |n=1⟩ Fock states. We also use the ability to ground-state cool to accurately measure the motional heating rate and report a reduction by almost 2 orders of magnitude compared with our previously measured result, which we attribute to carefully eliminating sources of electrical noise in the system.

Fabrication and operation of a two-dimensional ion-trap lattice on a high-voltage microchip

Microfabricated ion traps are a major advancement towards scalable quantum computing with trapped ions. The development of more versatile ion-trap designs, in which tailored arrays of ions are positioned in two dimensions above a microfabricated surface, will lead to applications in fields as varied as quantum simulation, metrology and atom-ion interactions. Current surface ion traps often have low trap depths and high heating rates, because of the size of the voltages that can be applied to them, limiting the fidelity of quantum gates. Here we report on a fabrication process that allows for the application of very high voltages to microfabricated devices in general and use this advance to fabricate a two-dimensional ion-trap lattice on a microchip. Our microfabricated architecture allows for reliable trapping of two-dimensional ion lattices, long ion lifetimes, rudimentary shuttling between lattice sites and the ability to deterministically introduce defects into the ion lattice.

Simple manipulation of a microwave dressed-state ion qubit

Many schemes for implementing quantum information processing require that the atomic states used have a nonzero magnetic moment; however, such magnetically sensitive states of an atom are vulnerable to decoherence due to fluctuating magnetic fields. Dressing an atom with external fields is a powerful method of reducing such decoherence [N. Timoney et al., Nature (London) 476, 185 (2011)]. We introduce an experimentally simpler method of manipulating such a dressed-state qubit, which allows the implementation of general rotations of the qubit, and demonstrate this method using a trapped ytterbium ion.

High-fidelity readout of trapped-ion qubits

We demonstrate single-shot qubit readout with a fidelity sufficient for fault-tolerant quantum computation. For an optical qubit stored in 40Ca+ we achieve 99.991(1)% average readout fidelity in 10(6) trials, using time-resolved photon counting. An adaptive measurement technique allows 99.99% fidelity to be reached in 145 micros average detection time. For 43Ca+, we propose and implement an optical pumping scheme to transfer a long-lived hyperfine qubit to the optical qubit, capable of a theoretical fidelity of 99.95% in 10 micros. We achieve 99.87(4)% transfer fidelity and 99.77(3)% net readout fidelity.

Polarization-controlled single photons

Vacuum-stimulated Raman transitions are driven between two magnetic substates of a 87Rb atom strongly coupled to an optical cavity. A magnetic field lifts the degeneracy of these states, and the atom is alternately exposed to laser pulses of two different frequencies. This produces a stream of single photons with alternating circular polarization in a predetermined spatiotemporal mode. MHz repetition rates are possible as no recycling of the atom between photon generations is required. Photon indistinguishability is tested by time-resolved two-photon interference.

Long-lived mesoscopic entanglement outside the Lamb-Dicke regime

We create entangled states of the spin and motion of a single 40Ca+ ion in a linear ion trap. We theoretically study and experimentally observe the behavior outside the Lamb-Dicke regime, where the trajectory in phase space is modified and the motional coherent states become squeezed. We directly observe the modification of the return time of the trajectory, and infer the squeezing. The mesoscopic entanglement is observed up to Deltaalpha=5.1 with coherence time 170 micros and mean phonon excitation n = 16.

High-efficiency detection of a single quantum of angular momentum by suppression of optical pumping

We propose and demonstrate experimentally the discrimination between two spin states of an atom purely on the basis of their angular momentum. The discrimination relies on angular momentum selection rules and does not require magnetic effects such as a magnetic dipole moment of the atom or an applied magnetic field. The central ingredient is to prevent by coherent population trapping an optical pumping process which would otherwise relax the spin state before a detectable signal could be obtained. We detected the presence or absence of a single quantum (h) of angular momentum in a trapped calcium ion in a single observation with success probability 0.86. As a practical technique, the method can be applied to read out some types of quantum computer.

Oxford ion-trap quantum computing project

We describe recent progress in the development of an ion-trap quantum information processor. We discuss the choice of ion species and describe recent experiments on read-out for a ground-state qubit and photoionization trap loading.