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By harnessing unique quantum mechanical phenomena, such as superposition and entanglement, quantum computers offer the possibility to drastically outperform classical computers for certain classes of problems. The realization of this potential, however, presents a substantial challenge, because noise and imperfections associated with the materials used to fabricate devices can obscure the delicate quantum mechanical effects that enable quantum computing. Hence, progress in synthesis, characterization, and modeling of materials for quantum computing have driven many exciting advances in recent years and will become increasingly important in the years to come. As progressively more complex, multi-qubit systems come online, and as significant government and industrial investment drives research forward, new challenges and opportunities for materials science continue to emerge. The articles in this issue survey the current state of materials science progress and obstacles for some leading quantum computing platforms; opportunities for deeper involvement by materials scientists abound. Ultimate realization of the full potential of quantum computers will require a multidisciplinary effort spanning many traditional areas of expertise.

Semiconductor quantum-dot spin qubits are a promising platform for quantum computation, because they are scalable and possess long coherence times. In order to realize this full potential, however, high-fidelity information transfer mechanisms are required for quantum error correction and efficient algorithms. Here, we present evidence of adiabatic quantum-state transfer in a chain of semiconductor quantum-dot electron spins. By adiabatically modifying exchange couplings, we transfer single- and two-spin states between distant electrons in less than 127 ns. We also show that this method can be cascaded for spin-state transfer in long spin chains. Based on simulations, we estimate that the probability to correctly transfer single-spin eigenstates and two-spin singlet states can exceed 0.95 for the experimental parameters studied here. In the future, state and process tomography will be required to verify the transfer of arbitrary single qubit states with a fidelity exceeding the classical bound. Adiabatic quantum-state transfer is robust to noise and pulse-timing errors. This method will be useful for initialization, state distribution, and readout in large spin-qubit arrays for gate-based quantum computing. It also opens up the possibility of universal adiabatic quantum computing in semiconductor quantum-dot spin qubits., Previous demonstrations of spin state transfer in quantum dot chains relied on physical motion of electrons or sequences of SWAP operations. Here, the authors implement an alternative method based on adiabatic evolution, offering advantages in terms of implementation and robustness to noise and errors.

We introduce a general setup for the analog quantum simulation of the dynamics of open quantum systems based on semiconductor quantum dots electrically connected to a chain of quantum $RLC$ electronic circuits. The dots are chosen to be in the regime of spin-charge hybridization to enhance their sensitivity to the $RLC$ circuits while mitigating the detrimental effects of unwanted noise. In this context, we establish an experimentally realizable map between the hybrid system and a qubit coupled to thermal harmonic environments of arbitrary complexity that enables the analog quantum simulation of open quantum systems. We assess the utility of the simulator by numerically exact emulations that indicate that the experimental setup can faithfully mimic the intended target even in the presence of its natural inherent noise. We further provide a detailed analysis of the physical requirements on the quantum dots and the $RLC$ circuits needed to experimentally realize this proposal that indicates that the simulator can be created with existing technology. The approach can exactly capture the effects of highly structured non-Markovian quantum environments typical of photosynthesis and chemical dynamics, and offer clear potential advantages over conventional and even quantum computation. The proposal opens a general path for effective quantum dynamics simulations based on semiconductor quantum dots.

The importance of disturbance Work in sea otters over the last few decades has transformed our understanding of the importance of specific species, or keystones, as drivers of community structure and stability. Foster et al . took the next step and tested whether otter foraging might influence genetic diversity in an eelgrass ecosystem (see the Perspective by Roman). The authors found that eelgrass genetic diversity was significantly higher where otters were present and that the impact was related to time: Longer otter presence was associated with higher genetic diversity. These results illustrate how the actions of a predator can affect the diversity of a producer in a tropic system. —SNV

Funding: This research was supported by a Mitacs Accelerate Internship (IT21479); the Save Our Seas Foundation; Willow Grove Foundation; Donner Canadian Foundation; Tides Canada; LUSH Charity Pot; private donations to North Coast Cetacean Society; Fisheries and Oceans Canada; and the Canada Nature Fund for Aquatic Species at Risk (CANAFSAR 2019-2021). Fin whales (Balaenoptera physalus) are widely considered an offshore and oceanic species, but certain populations also use coastal areas and semi-enclosed seas. Based upon fifteen years of study, we report that Canadian Pacific fin whales (B. p. velifera) have returned to the Kitimat Fjord System (KFS) in the Great Bear Rainforest, and have established a seasonally resident population in its intracoastal waters. This is the only fjord system along this coast or elsewhere in which fin whales are known to occur regularly with strong site fidelity. The KFS was also the only Canadian Pacific fjord system in which fin whales were commonly found and killed during commercial whaling, pointing to its long-term importance. Traditional knowledge, whaling records, and citizen science databases suggest that fin whales were extirpated from this area prior to their return in 2005-2006. Visual surveys and mark-recapture analysis documented their repopulation of the area, with 100-120 whales using the fjord system in recent years, as well as the establishment of a seasonally resident population with annual return rates higher than 70%. Line transect surveys identified the central and outer channels of the KFS as the primary fin whale habitat, with the greatest densities occurring in Squally Channel and Caamano Sound. Fin whales were observed in the KFS in most months of the year. Vessel- and shore-based surveys (27,311 km and 6,572 hours of effort, respectively) indicated regular fin whale presence (2,542 detections), including mother-calf pairs, from June to October and peak abundance in late August-early September. Seasonal patterns were variable year-to-year, and several lines of evidence indicated that fin whales arrived and departed from the KFS repeatedly throughout the summer and fall. Additionally, we report on the population's social network and morphometrics. These findings offer insights into the dynamics of population recovery in an area where several marine shipping projects are proposed. The fin whales of the Great Bear Rainforest represent a rare exception to general patterns in this species' natural history, and we highlight the importance of their conservation. Publisher PDF

Introduction. It is estimated that 50% of vaccines produced annu- ally are wasted because effectivity is dependent on protein structure and heat exposure disrupts the intermolecular interactions that maintain this structure. Since 90% of vaccines require a temperature- controlled supply chain, it is necessary to create a cold chain system to minimize vaccine waste. We have developed a more sustainable technology via the adsorption of Invasion Plasmid Antigen D (IpaD) onto mesoporous silica gels, improving the thermal stability of pro- tein-based therapeutics. Methods.xThe solution depletion method using UV-Vis was uti- lized to study the adsorption of IpaD onto silica gels. The silica-IpaD complex is heated above the denaturing temperature of the protein and then the IpaD is removed using N,N-Dimethyldodecylamine N-oxide (LDAO) and their secondary structure is tested using cir- cular dichroism (CD). Results. Pore diameter, pore volume and surface area were charac- terized for seven different silica gels. Silica gels designated as 6389, 6378, and 6375 had an adsorption percentage above 95% at pore volumes of 2.2, 2.8 and 3.8 cm3 mg-1, respectively. CD analyses con- firmed that the adsorbed IpaD after the heat treatment displayed a similar “W” shape CD signal as the native IpaD, indicating the con- servation of α-helices. In contrast, the unprotected IpaD after being exposed to high temperature shows a flat CD signal, demonstrating the loss of secondary structure. Conclusion. We have successfully increased the thermo-tolerance for IpaD using mesoporous silica and continue to further optimize mesoporous silica’s physiochemical properties to improve adsorption and desorption yields.

Recent work has demonstrated a new route to discrete time crystal physics in quantum spin chains by periodically driving nearest-neighbor exchange interactions in gate-defined quantum dot arrays [arXiv:2006.10913]. Here, we present a detailed analysis of exchange-driven Floquet physics in small arrays of GaAs quantum dots, including phase diagrams and additional diagnostics. We also show that emergent time-crystalline behavior can benefit the protection and manipulation of multi-spin states. For typical levels of nuclear spin noise in GaAs, the combination of driving and interactions protects spin-singlet states beyond what is possible in the absence of exchange interactions. We further show how to construct a time-crystal-inspired CZ gate between singlet-triplet qubits with high fidelity. These results show that periodically driving exchange couplings can enhance the performance of quantum dot spin systems for quantum information applications., Comment: 12 pages, 16 figures

Electron spins in silicon quantum dots are promising qubits due to their long coherence times, scalable fabrication, and potential for all-electrical control. However, charge noise in the host semiconductor presents a major obstacle to achieving high-fidelity single- and two-qubit gates in these devices. In this work, we measure the charge-noise spectrum of a Si/SiGe singlet-triplet qubit over nearly 12 decades in frequency using a combination of methods, including dynamically-decoupled exchange oscillations with up to 512 π pulses during the qubit evolution. The charge noise is colored across the entire frequency range of our measurements, although the spectral exponent changes with frequency. Moreover, the charge-noise spectrum inferred from conductance measurements of a proximal sensor quantum dot agrees with that inferred from coherent oscillations of the singlet-triplet qubit, suggesting that simple transport measurements can accurately characterize the charge noise over a wide frequency range in Si/SiGe quantum dots.

Because of their long coherence times and potential for scalability, semiconductor quantum-dot spin qubits hold great promise for quantum information processing. However, maintaining high connectivity between quantum-dot spin qubits, which favor linear arrays with nearest neighbor coupling, presents a challenge for large-scale quantum computing. In this work, we present evidence for long-distance spin-chain-mediated superexchange coupling between electron spin qubits in semiconductor quantum dots. We weakly couple two electron spins to the ends of a two-site spin chain. Depending on the spin state of the chain, we observe oscillations between the distant end spins. We resolve the dynamics of both the end spins and the chain itself, and our measurements agree with simulations. Superexchange is a promising technique to create long-distance coupling between quantum-dot spin qubits., Comment: 6+9 pages, 4+7 figures

Electron spins in silicon quantum dots are promising qubits due to their long coherence times, scalable fabrication, and potential for all-electrical control. However, charge noise in the host semiconductor presents a major obstacle to achieving high-fidelity single- and two-qubit gates in these devices. In this work, we measure the charge-noise spectrum of a Si/SiGe singlet-triplet qubit over nearly 12 decades in frequency using a combination of methods, including dynamically-decoupled exchange oscillations with up to 512 {\pi} pulses during the qubit evolution. The charge noise is colored across the entire frequency range of our measurements, although the spectral exponent changes with frequency. Moreover, the charge-noise spectrum inferred from conductance measurements of a proximal sensor quantum dot agrees with that inferred from coherent oscillations of the singlet-triplet qubit, suggesting that simple transport measurements can accurately characterize the charge noise over a wide frequency range in Si/SiGe quantum dots., Comment: Main: 10 pg, 5 fig. Supp: 15 pg, 11 fig. Supp Notes: Hadamard gate calibration, t_{meas}, dBz and J_{min}, Charge-noise v temp. Supp Figs: Readout, FID, CPMG filter function, Echo analysis, Noise extraction error from CPMG, Samp rate in three-day FID, Charge-noise correlations, Charge-sensor spectra, Automated Hadamard calibration, dBz v B_{ext}, Echo v temp. Supp Tables: Lever arms, t_{meas}

The Deep Underground Neutrino Experiment (DUNE) is an international, world-class experiment aimed at exploring fundamental questions about the universe that are at the forefront of astrophysics and particle physics research. DUNE will study questions pertaining to the preponderance of matter over antimatter in the early universe, the dynamics of supernovae, the subtleties of neutrino interaction physics, and a number of beyond the Standard Model topics accessible in a powerful neutrino beam. A critical component of the DUNE physics program involves the study of changes in a powerful beam of neutrinos, i.e., neutrino oscillations, as the neutrinos propagate a long distance. The experiment consists of a near detector, sited close to the source of the beam, and a far detector, sited along the beam at a large distance. This document, the DUNE Near Detector Conceptual Design Report (CDR), describes the design of the DUNE near detector and the science program that drives the design and technology choices. The goals and requirements underlying the design, along with projected performance are given. It serves as a starting point for a more detailed design that will be described in future documents. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Electron spins in silicon quantum dots are excellent qubits because they have long coherence times, high gate fidelities, and are compatible with advanced semiconductor manufacturing techniques. The valley degree of freedom, which results from the specific character of the Si band structure, is a unique feature of electrons in Si spin qubits. However, the small difference in energy between different valley levels often poses a challenge for quantum computing in Si. Here, we show that the spin-valley coupling in Si, which enables transitions between states with different spin and valley quantum numbers, enables coherent control of electron spins in Si. We demonstrate coherent manipulation of effective single- and two-electron spin states in a Si/SiGe double quantum dot without ac magnetic or electric fields. Our results illustrate that the valley degree of freedom, which is often regarded as an inconvenience, can itself enable quantum manipulation of electron spin states.

Approximately half of all vaccines produced annually are wasted because effectivity is dependent on protein structure and heat exposure disrupts the intermolecular interactions needed to maintain the structure. Thus, most vaccines require a temperature-controlled supply chain to minimize waste. A more sustainable technology was developed via the adsorption of invasion plasmid antigen D (IpaD) onto mesoporous silica, improving the thermal stability of this protein-based therapeutic. Seven silicas were characterized to determine the effects of pore diameter, pore volume, and surface area on protein adsorption. The silica-IpaD complex was then heated above the IpaD denaturing temperature and N,N-dimethyldodecylamine N-oxide was used to remove IpaD from the silica. Circular dichroism confirmed that the adsorbed IpaD after the heat treatment maintained a native secondary structure rich in α-helix content. In contrast, the unprotected IpaD after heat treatment lost its secondary structure. Isotherms using Langmuir, Freundlich, and Temkin models demonstrated that the adsorption of IpaD onto silicas is best fit by the Langmuir model. If pores are less than 15 nm, adsorption is negligible. If the pores are between 15 and 25 nm, then monolayer coverage is achieved and IpaD is protected from thermal denaturing. If pores are larger than 25 nm, the adsorption is a multilayer coverage and it is easier to remove the protein from the silica because of a less-developed hydrogen bond network. This case study provides strong evidence that IpaD is thermally stabilized via adsorption on mesoporous silica with the proper range of pore sizes.

Heisenberg exchange coupling between neighboring electron spins in semiconductor quantum dots provides a powerful tool for quantum information processing and simulation. Although so far unrealized, extended Heisenberg spin chains can enable long-distance quantum information transfer and the generation of non-equilibrium quantum states. In this work, we implement simultaneous, coherent exchange coupling between all nearest-neighbor pairs of spins in a quadruple quantum dot. The main challenge in implementing simultaneous exchange couplings is the nonlinear and nonlocal dependence of the exchange couplings on gate voltages. Through a combination of electrostatic simulation and theoretical modeling, we show that this challenge arises primarily due to lateral shifts of the quantum dots during gate pulses. Building on this insight, we develop two models, which can be used to predict the confinement gate voltages for a desired set of exchange couplings. Although the model parameters depend on the number of exchange couplings desired (suggesting that effects in addition to lateral wavefunction shifts are important), the models are sufficient to enable simultaneous and independent control of all three exchange couplings in a quadruple quantum dot. We demonstrate two-, three-, and four-spin exchange oscillations, and our data agree with simulations., Comment: 9+10 pages, 5+5 figures

Vessel strikes are a source of mortality and injury for baleen whales, which can have population-level impacts. Spatial analysis of whale and marine traffic distributions provides a valuable approach for identifying zones with high collision risk. We conducted 34 systematic aerial surveys to estimate humpback Megaptera novaeangliae and fin whale Balaenoptera physalus densities off the west coast of Vancouver Island, Canada, including approaches to major shipping lanes in Juan de Fuca Strait, a gateway to the ports of southern British Columbia and Washington State. To predict whale densities, we fit negative binomial generalized additive models (GAMs) to sightings data, incorporating survey effort as an offset, and depth, slope, and latitude as environmental covariates. Humpbacks were primarily observed on the continental shelf, with highest predicted densities along the shelf edge (~200 m isobath), whereas fin whales were primarily distributed west of the shelf break (>450 m depth). We combined GAM-predicted whale densities with vessel traffic data to estimate the relative risk of ship strikes. Since vessel speed is an important determinant of lethality, we also calculated the relative risk of lethal injuries, given the probability that a collision occurs. Humpbacks were most likely to be struck along the shelf edge, the inshore approaches to Juan de Fuca Strait, and within the strait itself. Fin whales were most likely to be struck in the offshore approaches to Juan de Fuca and inside the western portion of the strait. Our study is the first to assess ship strike risk in this region of high whale density and marine traffic use.

Sarcocystis neurona was recognised as an important cause of mortality in southern sea otters (Enhydra lutris nereis) after an outbreak in April 2004 and has since been detected in many marine mammal species in the Northeast Pacific Ocean. Risk of S. neurona exposure in sea otters is associated with consumption of clams and soft-sediment prey and is temporally associated with runoff events. We examined the spatial distribution of S. neurona exposure risk based on serum antibody testing and assessed risk factors for exposure in animals from California, Washington, British Columbia and Alaska. Significant spatial clustering of seropositive animals was observed in California and Washington, compared with British Columbia and Alaska. Adult males were at greatest risk for exposure to S. neurona, and there were strong associations with terrestrial features (wetlands, cropland, high human housing-unit density). In California, habitats containing soft sediment exhibited greater risk than hard substrate or kelp beds. Consuming a diet rich in clams was also associated with increased exposure risk. These findings suggest a transmission pathway analogous to that described for Toxoplasma gondii, with infectious stages traveling in freshwater runoff and being concentrated in particular locations by marine habitat features, ocean physical processes, and invertebrate bioconcentration.

Silicon spin qubits show great promise as a scalable qubit platform for fault-tolerant quantum computing. However, fast high-fidelity readout of charge and spin states, which is required for quantum error correction, has remained elusive. Radio-frequency reflectometry enables rapid high-fidelity readout of $\mathrm{Ga}\mathrm{As}$ spin qubits, but the large capacitances between accumulation gates and the underlying two-dimensional electron gas in accumulation-mode $\mathrm{Si}$ quantum-dot devices, as well as the relatively low two-dimensional electron gas mobilities, have made radio-frequency reflectometry challenging in these platforms. In this work, we implement radio-frequency reflectometry in a $\mathrm{Si}$/$\mathrm{Si}\text{\ensuremath{-}}\mathrm{Ge}$ quantum-dot device with overlapping gates by making minor device-level changes that eliminate these challenges. We demonstrate charge-state readout with a fidelity above $99.9\mathrm{%}$ in an integration time of $300\phantom{\rule{0.2em}{0ex}}\mathrm{ns}$. We measure the singlet and triplet states of a double quantum dot via both conventional Pauli spin blockade and a charge latching mechanism, and we achieve maximum fidelities of $82.9$ and $99.0\mathrm{%}$ in $2.08$- and $1.6$-$\ensuremath{\mu}\mathrm{s}$ integration times, respectively. We also use radio-frequency reflectometry to perform single-shot readout of single-spin states via spin-selective tunneling in microsecond-scale integration times.

The transfer of information between quantum systems is essential for quantum communication and computation. In quantum computers, high connectivity between qubits can improve the efficiency of algorithms, assist in error correction, and enable high-fidelity readout. However, as with all quantum gates, operations to transfer information between qubits can suffer from errors associated with spurious interactions and disorder between qubits, among other things. Here, we harness interactions and disorder between qubits to improve a swap operation for spin eigenstates in semiconductor gate-defined quantum-dot spins. We use a system of four electron spins, which we configure as two exchange-coupled singlet–triplet qubits. Our approach, which relies on the physics underlying discrete time crystals, enhances the quality factor of spin-eigenstate swaps by up to an order of magnitude. Our results show how interactions and disorder in multi-qubit systems can stabilize non-trivial quantum operations and suggest potential uses for non-equilibrium quantum phenomena, like time crystals, in quantum information processing applications. Our results also confirm the long-predicted emergence of effective Ising interactions between exchange-coupled singlet–triplet qubits., Information transfer between distant qubits suffers from spurious interactions and disorder. Here, the authors report up to an order of magnitude enhancement in the quality factor of a swap operation of eigenstates in a quantum dot chain, by using a periodic driving protocol inspired by discrete time crystals.

Electron spins in silicon have long coherence times and are a promising qubit platform. However, electric field noise in semiconductors poses a challenge for most single- and multi-qubit operations in quantum-dot spin qubits. Here, we investigate the dependence of low-frequency charge noise spectra on temperature and aluminum-oxide gate dielectric thickness in Si/SiGe quantum dots with overlapping gates. We find that charge noise increases with aluminum oxide thickness. We also find strong dot-to-dot variations in the temperature dependence of the noise magnitude and spectrum. These findings suggest that each quantum dot experiences noise caused by a distinct ensemble of two-level systems, each of which has a non-uniform distribution of thermal activation energies. Taken together, our results suggest that charge noise in Si/SiGe quantum dots originates at least in part from a non-uniform distribution of two-level systems near the surface of the semiconductor., v3: 12 pages, 6 figures. Includes corrections to figures F3, F4, and S2 as reported in Erratum to published version

Quantum information science has the potential to revolutionize modern technology by providing resource-efficient approaches to computing

Electron spins in semiconductor quantum dots are a promising platform for quantum-information processing applications because their quantum phase coherence can persist for extremely long times. Nearest-neighbor electron spins naturally interact with each other via Heisenberg exchange coupling. Heisenberg exchange coupling results from the interplay of the electrostatic confinement potential together with the Pauli exclusion principle, which requires that no two electrons can have the same quantum number. Exchange coupling enables a host of useful capabilities, including the generation of different types of qubits, multi-qubit gates, ways to increase connectivity in systems of quantum-dot spin qubits, and routes to explore intriguing many-body phenomena.

A discrete time crystal is a recently discovered non-equilibrium phase of matter that has been shown to exist in disordered, periodically driven Ising spin chains. In this phase, if the system is initially prepared in one of a certain class of pure multispin product states, it periodically returns to this state over very long time scales despite the presence of interactions, disorder, and pulse imperfections. Here, we show that this phase occurs in GaAs quantum dot spin arrays containing as few as three quantum dots, each confining one electron spin, for naturally occurring levels of nuclear spin noise and charge noise. Although the physical interaction in these arrays is a nearest-neighbor Heisenberg exchange interaction, we show that this can be effectively converted into an Ising interaction by applying additional pulses during each drive period. We show that by changing the rotation axis of these pulses, we can select the direction of the Ising interaction and, consequently, the quantization axis of the stabilized multispin states. Moreover, we demonstrate that it is possible to perform coherent rotations of the stabilized states while remaining in the time crystal phase. These findings open up the intriguing possibility of using time crystal phases to extend the lifetime of quantum states for information applications., 11 pages, 14 figures, PRB version

The conservation and management of sea otters has benefited from a dedicated research effort over the past 60 years enabling this species to recover from a few thousand in the early 20th century to about 150,000 today. Continued research to allow full, pre-exploitation recovery and restoration of nearshore ecosystems should focus on at least seven key challenges: (1) Defining sea otter populations at smaller spatial scales that reflect this species’ life history and dispersal patterns; (2) Understanding factors that regulate sea otter population density with a focus on index sites that are representative of the variety of littoral habitats occupied by sea otters around the North Pacific Rim; (3) Quantifying the effects of sea otters on the littoral community with a focus on how food availability limits population and ecosystem recovery and on predicting the effect of sea otter reoccupation on commercially valuable invertebrates; (4) Making sea otter monitoring programs comparable across geo-political boundaries through international collaboration to optimize survey efforts both spatially and temporally and to determine the cause of changes in sea otter demographics; (5) Evaluating the conservation benefits of sea otter reintroductions into historical habitat; (6) Assessing the socioeconomic costs and benefits of sea otter range expansion to anticipate and mitigate conflicts; (7) Recognizing in conservation and management plans that sea otters can be significantly affected by higher level predators in some circumstances. Many of these challenges will require new tools including the next generation geolocation tag technology that will allow assessments of long-range movements, dispersal and gene flow in various populations.

Quantum information science has the potential to revolutionize modern technology by providing resource-efficient approaches to computing, communication, and sensing. Although the physical qubits in a realistic quantum device will inevitably suffer errors, quantum error correction creates a path to fault-tolerant quantum information processing. Quantum error correction, however, requires that individual qubits can interact with many other qubits in the processor. Engineering this high connectivity can pose a challenge for platforms like electron spin qubits that naturally favor linear arrays. Here, we present an experimental demonstration of the transmission of electron spin states via Heisenberg exchange in an array of spin qubits. We transfer both single-spin and entangled states back and forth in a quadruple quantum-dot array without moving any electrons. Because it is scalable to large numbers of qubits, state transfer through Heisenberg exchange will be especially useful for multi-qubit gates and error-correction in spin-based quantum computers., Comment: 14 pages, 10 figures

Among the different platforms for quantum information processing, individual electron spins in semiconductor quantum dots stand out for their long coherence times and potential for scalable fabrication. The past years have witnessed substantial progress in the capabilities of spin qubits. However, coupling between distant electron spins, which is required for quantum error correction, presents a challenge, and this goal remains the focus of intense research. Quantum teleportation is a canonical method to transmit qubit states, but it has not been implemented in quantum-dot spin qubits. Here, we present evidence for quantum teleportation of electron spin qubits in semiconductor quantum dots. Although we have not performed quantum state tomography to definitively assess the teleportation fidelity, our data are consistent with conditional teleportation of spin eigenstates, entanglement swapping, and gate teleportation. Such evidence for all-matter spin-state teleportation underscores the capabilities of exchange-coupled spin qubits for quantum-information transfer., Comment: 12+27 pages, 4+15 figures

Pathogens entering the marine environment as pollutants exhibit a spatial signature driven by their transport mechanisms. The sea otter ( Enhydra lutris ), a marine animal which lives much of its life within sight of land, presents a unique opportunity to understand land–sea pathogen transmission. Using a dataset on Toxoplasma gondii prevalence across sea otter range from Alaska to California, we found that the dominant drivers of infection risk vary depending upon the spatial scale of analysis. At the population level, regions with high T. gondii prevalence had higher human population density and a greater proportion of human-dominated land uses, suggesting a strong role for population density of the felid definitive host of this parasite. This relationship persisted when a subset of data were analysed at the individual level: large-scale patterns in sea otter T. gondii infection prevalence were largely explained by individual exposure to areas of high human housing unit density, and other landscape features associated with anthropogenic land use, such as impervious surfaces and cropping land. These results contrast with the small-scale, within-region analysis, in which age, sex and prey choice accounted for most of the variation in infection risk, and terrestrial environmental features provided little variation to help in explaining observed patterns. These results underscore the importance of spatial scale in study design when quantifying both individual-level risk factors and landscape-scale variation in infection risk.

BackgroundFew studies have described clinical characteristics of patients subject to an involuntary detention in an Irish context. The Irish Mental Health Act 2001 makes provision under Section 23(1), whereby a person who has voluntary admission status can be detained.AimsThis study aimed to describe all involuntary admissions to St Patrick’s University Hospital (SPUH) (2011–2013) and to evaluate clinical characteristics of voluntary patients who underwent Mental Health Act assessment during 2011 to determine differences in those who had involuntary admission orders completed and those who did not.MethodsAll uses of Mental Health Act 2001 within SPUH 2011–2013 were identified. All uses of Section 23(1) during 2011 were reviewed and relevant documents/case-notes examined using a pro forma covering clinical data, factors recognized to influence involuntary admissions and validated scales were used to determine diagnoses, insight, suicide and violence risk.ResultsOver 2011–2013, 2.5–3.8% of all admissions were involuntary with more detained after use of Section 23(1) than Section 14(2). The majority of initiations of Section 23(1) did not result in an involuntary admission (72%), occurred out of hours (52%) and many occurred early after admission (p=0.001), suicide risk (p=0.03) and lack of patient insight into treatment (p=0.007) predicted conversion to involuntary admission.ConclusionThis study predicts a role for patient insight, suicide risk and consultant psychiatrist decision making in the initiation of Mental Health Act assessment of voluntary patients. Further data describing the involuntary admissions process in an Irish setting are needed.

Participating NGO evaluation report. (DOCX 24Â kb)

Visibility of singlet-triplet qubit readout is reduced to almost zero in large magnetic field gradients due to relaxation processes. Here we present a new readout technique that is robust against relaxation and allows for measurement when previously studied methods fail. This technique maps the qubit onto spin states that are immune to relaxation using a spin-dependent electron tunneling process between the qubit and the lead. We probe this readout's performance as a function of magnetic field gradient and applied magnetic field, and optimize the pulse applied to the qubit through experiment and simulation.

The quantification of individuality is a common research theme in the fields of population, community, and evolutionary ecology. The potential for individuality to arise is likely context-dependent, and the influence of habitat characteristics on its prevalence has received less attention than intraspecific competition. We examined individual diet specialization in 16 sea otter (Enhydra lutris) populations from southern California to the Aleutian Islands in Alaska. Because population histories, relative densities, and habitat characteristics vary widely among sites, we could examine the effects of intraspecific competition and habitat on the prevalence of individual diet specialization. Using observed diet data, we classified half of our sites as rocky substrate habitats and the other half containing a mixture of rocky and unconsolidated (soft) sediment substrates. We used stable isotope data to quantify population- and individual-level diet variation. Among rocky substrate sites, the slope [±standard error (SE)] of the positive significant relationship between the within-individual component (WIC) and total isotopic niche width (TINW) was shallow (0.23 ± 0.07) and negatively correlated with sea otter density. In contrast, the slope of the positive WIC/TINW relationship for populations inhabiting mixed substrate habitats was much higher (0.53 ± 0.14), suggesting a low degree of individuality, irrespective of intraspecific competition. Our results show that the potential for individuality to occur as a result of increasing intraspecific competition is context-dependent and that habitat characteristics, which ultimately influence prey diversity, relative abundance, and the range of skillsets required for efficient prey procurement, are important in determining when and where individual diet specialization occurs in nature.

Pathogens entering the marine environment as pollutants exhibit a spatial signature driven by their transport mechanisms. The sea otter (Enhydra lutris), a marine animal which lives much of its life within sight of land, presents a unique opportunity to understand land–sea pathogen transmission. Using a dataset on Toxoplasma gondii prevalence across sea otter range from Alaska to California, we found that the dominant drivers of infection risk vary depending upon the spatial scale of analysis. At the population level, regions with high T. gondii prevalence had higher human population density and a greater proportion of human-dominated land uses, suggesting a strong role for population density of the felid definitive host of this parasite. This relationship persisted when a subset of data were analysed at the individual level: large-scale patterns in sea otter T. gondii infection prevalence were largely explained by individual exposure to areas of high human housing unit density, and other landscape features associated with anthropogenic land use, such as impervious surfaces and cropping land. These results contrast with the small-scale, within-region analysis, in which age, sex and prey choice accounted for most of the variation in infection risk, and terrestrial environmental features provided little variation to help in explaining observed patterns. These results underscore the importance of spatial scale in study design when quantifying both individual-level risk factors and landscape-scale variation in infection risk.

Real-time passive acoustic monitoring (PAM) was conducted as part of the first large-scale systematic survey of marine mammal distribution and abundance in territorial outer-coastal waters off western Canada. The survey was conducted for approximately five weeks, from early July to mid-August, 2018 using a 69-m Canadian Coast Guard and Fisheries Vessel. A four-element, towed hydrophone array and sonobuoys (type AN/SSQ-53F and AN/SSQ-53G) were deployed and monitored in real-time 24/7 by experienced bio-acousticians. The towed array was deployed for approximately 640 h (78% of the time underway). Approximately 145 independent detections of marine mammals were made. Sperm whales (n = 53) and porpoises (n= 49) represented just over two-thirds of all detections. Ten near real-time localizations of sperm whales and 31 localization of porpoises were made, representing just over 60% of all (n = 67) all high-quality localizations. Sonobuoy effort consisted of semi-systematic deployments day and night and when sightings of large baleen whales occurred. A total of 112 sonobuoys were deployed successfully and monitored in directional (DIFAR) mode. Marine mammal calls were recorded on 32% (36) of sonobuoys. Sonobuoy detections included killer whales calls and clicks, sperm whale clicks, dolphin clicks, fin whale calls, and blue whale calls (both B and D type calls).

We present experimental data and associated theory for correlations in a series of experiments involving repeated Landau-Zener sweeps through the crossing point of a singlet state and a spin aligned triplet state in a GaAs double quantum dot containing two conduction electrons, which are loaded in the singlet state before each sweep, and the final spin is recorded after each sweep. The experiments reported here measure correlations on time scales from 4 $\mu$s to 2 ms. When the magnetic field is aligned in a direction such that spin-orbit coupling cannot cause spin flips, the correlation spectrum has prominent peaks centered at zero frequency and at the differences of the Larmor frequencies of the nuclei, on top of a frequency-independent background. When the spin-orbit field is relevant, there are additional peaks, centered at the frequencies of the individual species. A theoretical model which neglects the effects of high-frequency charge noise correctly predicts the positions of the observed peaks, and gives a reasonably accurate prediction of the size of the frequency-independent background, but gives peak areas that are larger than the observed areas by a factor of two or more. The observed peak widths are roughly consistent with predictions based on nuclear dephasing times of the order of 60 $\mu$s. However, there is extra weight at the lowest observed frequencies, which suggests the existence of residual correlations on the scale of 2 ms. We speculate on the source of these discrepancies., Comment: 20 pages, 5 figures, 2 tables

Electron spins in semiconductors are promising qubits because their long coherence times enable nearly 10^9 coherent quantum gate operations. However, developing a scalable high-fidelity two-qubit gate remains challenging. Here, we demonstrate an entangling gate between two double-quantum-dot spin qubits in GaAs by using a magnetic field gradient between the two dots in each qubit to suppress decoherence due to charge noise. When the magnetic gradient dominates the voltage-controlled exchange interaction between electrons, qubit coherence times increase by an order of magnitude. Using randomized benchmarking and self-consistent quantum measurement, state, and process tomography, we measure single-qubit gate fidelities of approximately 99% and an entangling gate fidelity of 90%. In the future, operating double quantum dot spin qubits with large gradients in nuclear-spin-free materials, such as Si, should enable a two-qubit gate fidelity surpassing the threshold for fault-tolerant quantum information processing., Comment: 6+6 pages, 4 figures

A Viewpoint on: Realization of Microwave Quantum Circuits Using Hybrid Superconducting-Semiconducting Nanowire Josephson Elements G. de Lange, B. van Heck, A. Bruno, D. J. van Woerkom, A. Geresdi, S. R. Plissard, E. P.A.M. Bakkers, A.R. Akhmerov, and L. DiCarlo Physical Review Letters 115, 127002 2015 – Published September 14, 2015 Semiconductor-Nanowire-Based Superconducting Qubit T.W. Larsen, K.D. Petersson, F. Kuemmeth, T. S. Jespersen, P. Krogstrup, J. Nygard, and C.M. Marcus Physical Review Letters 115, 127001 2015 – Published September 14, 2015