414 research outputs found
A Universal Theory of Spin Squeezing
We provide extensive numerical and analytic evidence for the following
conjecture: Any Hamiltonian exhibiting finite temperature, easy-plane
ferromagnetism (XY order) can be used to generate scalable spin squeezing, and
thus to perform quantum-enhanced sensing. Our conjecture is guided by a deep
connection between the quantum Fisher information of pure states and the
spontaneous breaking of a continuous symmetry. We demonstrate that
spin-squeezing exhibits a phase diagram with a sharp transition between
scalable squeezing and non-squeezing. This transition coincides with the
equilibrium phase boundary for XY order at a finite temperature. In the
scalable squeezing phase, we predict a sensitivity scaling as ,
between the standard quantum limit, , and that achieved in all-to-all
coupled easy-plane spin models, . Our results provide fundamental
insight into the landscape of Hamiltonians that can be used to generate
metrologically useful quantum states.Comment: 6 pages, 3 figures + 12 pages, 6 figure
Integrating research using animal-borne telemetry with the needs of conservation management
Animal-borne telemetry has revolutionized our ability to study animal movement, species physiology, demography and social structures, changing environments and the threats that animals are experiencing. While there will always be a need for basic ecological research and discovery, the current conservation crisis demands we look more pragmatically at the data required to make informed management decisions. Here, we define a framework that distinguishes how research using animal telemetry devices can influence conservation. We then discuss two critical questions which aim to directly connect telemetry-derived data to applied conservation decision-making: (i) Would my choice of action change if I had more data? (ii) Is the expected gain worth the money and time required to collect more data? Policy implications. To answer questions about integrating telemetry-derived data with applied conservation, we suggest the use of value of information analysis to quantitatively assess the return-on-investment of animal telemetry-derived data for conservation decision-making
Scalable spin squeezing in a dipolar Rydberg atom array
The standard quantum limit bounds the precision of measurements that can be
achieved by ensembles of uncorrelated particles. Fundamentally, this limit
arises from the non-commuting nature of quantum mechanics, leading to the
presence of fluctuations often referred to as quantum projection noise. Quantum
metrology relies on the use of non-classical states of many-body systems in
order to enhance the precision of measurements beyond the standard quantum
limit. To do so, one can reshape the quantum projection noise -- a strategy
known as squeezing. In the context of many-body spin systems, one typically
utilizes all-to-all interactions (e.g. the one-axis twisting model) between the
constituents to generate the structured entanglement characteristic of spin
squeezing. Motivated by recent theoretical work, here we explore the prediction
that short-range interactions -- and in particular, the two-dimensional dipolar
XY model -- can also enable the realization of scalable spin squeezing. Working
with a dipolar Rydberg quantum simulator of up to 100 atoms, we demonstrate
that quench dynamics from a polarized initial state lead to spin squeezing that
improves with increasing system size up to a maximum of -3.5 dB (prior to
correcting for detection errors, or approximately -5 dB after correction).
Finally, we present two independent refinements: first, using a multistep
spin-squeezing protocol allows us to further enhance the squeezing by
approximately 1 dB, and second, leveraging Floquet engineering to realize
Heisenberg interactions, we demonstrate the ability to extend the lifetime of
the squeezed state by freezing its dynamics.Comment: 12 pages, 10 figure
Preference versus performance: Investigating the dissociation between objective measures and subjective ratings of usability for schematic metro maps and intuitive theories of design
Three experiments are reported in which objective measures and subjective ratings of schematic metro map usability were investigated. Experiment 1 used a within-subjects design to compare octolinear and curvilinear Paris Metro maps. This replicated and extended Roberts et al. (2013); the curvilinear map was associated with faster journey planning times, and yet preference between the two was unrelated to this measure. In Experiment 2, nine matched versions of the London Underground map were rated for usability and attractiveness, and a clear octolinear bias was displayed. It was also possible to identify individuals who held a simplicity theory of effective design, versus an octolinearity theory. Experiment 3 investigated the relationship between usability ratings and journey planning times for three Berlin network maps, all optimized for simplicity of line trajectories. No differences in times were found, and yet usability ratings after experience at using the maps differed significantly, in line with the findings for the London designs in Experiment 2. Overall, the dissociation between objective measures of performance and subjective ratings of usability is robust, and appears to reflect expectations and prejudices concerning effective design. The octolinearity as a gold standard conjecture for achieving optimum usability continues to be refuted
Reciprocal Relations Between Emotional Self-Efficacy Beliefs and Ego-Resiliency Across Time
The present study examined the longitudinal relations of adolescents' self-reported ego-resiliency to their emotional self-efficacy beliefs in expressing positive emotions and in managing negative emotions as they moved into early adulthood. Participants were 239 females and 211 males with a mean age of 17 years (SD = .80) at T1, 19 years (SD = .80) at T2, 21 years (SD = .82) at T3, and 25 years (SD = .80) at T4. A four-wave cross-lagged regression model and mediational analyses were used. In a panel structural equation model controlling for the stability of the constructs, reciprocal relationships across time were found between ego-resiliency and emotional self-efficacy beliefs related to the expression of positive emotions and to the management of negative emotions. Moreover, the relation between ego-resiliency assessed at T1 and T3, and ego-resiliency assessed at T2 and T4, was mediated through emotional self-efficacy beliefs (at T2 and T3, respectively), and vice versa. The posited conceptual model accounted for a significant portion of variance in ego-resiliency and has implications for understanding the development of ego-resiliency
Evaluation of MPA designs that protect highly mobile megafauna now and under climate change scenarios
Marine protected area (MPA) designs, including large-scale MPAs (LSMPAs; \u3e150,000 km2), mobile MPAs (fluid spatiotemporal boundaries), and MPA networks, may offer different benefits to species and could enhance protection by encompassing spatiotemporal scales of animal movement. We sought to understand how well LSMPAs could benefit nine highly-mobile marine species in the tropics now and into the future by: 1) evaluating current range overlap within a LSMPA; 2) evaluating range overlap under climate change projections; and 3) evaluating how well theoretical MPA designs benefit these nine species. We focused on Palmyra Atoll and Kingman Reef, a 2000 km2 area within the 1.2 million km2 U.S. Pacific Remote Islands Marine National Monument (PRIMNM) that contains marine megafauna (reef and pelagic fishes; sea turtles; seabirds; cetaceans) reflecting different behaviors and habitat use. Our approach is useful for evaluating the effectiveness of the Palmyra-Kingman MPA and PRIMNM in protecting these species, and tropical LSMPAs in general, and for informing future MPA design. Stationary MPAs provided protection at varying scales. Reef manta rays (Mobula alfredi), grey reef sharks (Carcharhinus amblyrhynchos), green sea turtles (Chelonia mydas), and bottlenose dolphins (Tursiops truncatus) had overall small ranges (\u3c100 km from Palmyra-Kingman) and could benefit from stationary MPAs that contained heterogenous reef habitats. Yellowfin tuna (Thunnus albacares), sooty terns (Onychoprion fuscatus), red-footed boobies (Sula sula), great frigatebirds (Fregata minor), and melon-headed whales (Peponocephala electra) navigated complex oceanographic processes and may benefit most from mobile MPAs that shift with features including thermal fronts, cyclic regions of elevated productivity, and eddies, if relationships with these features are established and predictable. All species had capacity to travel to nearby reef systems, illustrating potential benefits of MPA networks and protected corridors. Suitable habitats will likely contract for all species as warm water expands under climate change scenarios (species habitats were predicted to decrease by 4–49% at Palmyra-Kingman) and MPAs may not protect suitable habitats into the future. Species habitat requirements and movement ecologies are critical aspects of marine spatial planning, especially with respect to dynamic ocean processes and a changing climate
- …