Improved Three-Dimensional Resistivity Data Acquisition Capabilities at the Hanford Site - 14146

The recent 3D electrical resistivity characterization at 241_U Tank Farm represents the first full-farm true 3D environmental resistivity deployment in the world. Technological and manufacturing developments by the vendor resulted in a data acquisition system that far surpasses the ability of the previous off-the-shelf systems. The new data acquisition system allows for 180 channels, which enables the full-farm 3D acquisition without the inaccuracies associated with combining multiple datasets. This ultimately leads to a more accurate model of the subsurface and a better understanding of moisture and contaminant distribution within the vadose zone. Additionally, advancements in electrical noise filters and increased output power resulted in better quality data than previously acquired at the site, reducing the amount of poor quality data by more than half. Ultimately, the new, improved system increased the speed of data acquisition and quality of the final results. The system allowed a reduction in field labor and field work duration to half the field budget estimates, resulting in a 25% reduction in overall project costs. The new resistivity data acquisition system represents technological advancements resulting in a greater quantity of data with decreased project costs

Suppressing quantum errors by scaling a surface code logical qubit

Practical quantum computing will require error rates that are well below what is achievable with physical qubits. Quantum error correction offers a path to algorithmically-relevant error rates by encoding logical qubits within many physical qubits, where increasing the number of physical qubits enhances protection against physical errors. However, introducing more qubits also increases the number of error sources, so the density of errors must be sufficiently low in order for logical performance to improve with increasing code size. Here, we report the measurement of logical qubit performance scaling across multiple code sizes, and demonstrate that our system of superconducting qubits has sufficient performance to overcome the additional errors from increasing qubit number. We find our distance-5 surface code logical qubit modestly outperforms an ensemble of distance-3 logical qubits on average, both in terms of logical error probability over 25 cycles and logical error per cycle ($2.914\%\pm 0.016\%$ compared to $3.028\%\pm 0.023\%$). To investigate damaging, low-probability error sources, we run a distance-25 repetition code and observe a $1.7\times10^{-6}$ logical error per round floor set by a single high-energy event ($1.6\times10^{-7}$ when excluding this event). We are able to accurately model our experiment, and from this model we can extract error budgets that highlight the biggest challenges for future systems. These results mark the first experimental demonstration where quantum error correction begins to improve performance with increasing qubit number, illuminating the path to reaching the logical error rates required for computation.Comment: Main text: 6 pages, 4 figures. v2: Update author list, references, Fig. S12, Table I

Non-Abelian braiding of graph vertices in a superconducting processor

Indistinguishability of particles is a fundamental principle of quantum mechanics. For all elementary and quasiparticles observed to date - including fermions, bosons, and Abelian anyons - this principle guarantees that the braiding of identical particles leaves the system unchanged. However, in two spatial dimensions, an intriguing possibility exists: braiding of non-Abelian anyons causes rotations in a space of topologically degenerate wavefunctions. Hence, it can change the observables of the system without violating the principle of indistinguishability. Despite the well developed mathematical description of non-Abelian anyons and numerous theoretical proposals, the experimental observation of their exchange statistics has remained elusive for decades. Controllable many-body quantum states generated on quantum processors offer another path for exploring these fundamental phenomena. While efforts on conventional solid-state platforms typically involve Hamiltonian dynamics of quasi-particles, superconducting quantum processors allow for directly manipulating the many-body wavefunction via unitary gates. Building on predictions that stabilizer codes can host projective non-Abelian Ising anyons, we implement a generalized stabilizer code and unitary protocol to create and braid them. This allows us to experimentally verify the fusion rules of the anyons and braid them to realize their statistics. We then study the prospect of employing the anyons for quantum computation and utilize braiding to create an entangled state of anyons encoding three logical qubits. Our work provides new insights about non-Abelian braiding and - through the future inclusion of error correction to achieve topological protection - could open a path toward fault-tolerant quantum computing

Investigating stress path hysteresis in a CO2 injection scenario using coupled geomechanical-fluid flow modelling

A successful CO2 storage project will require large volumes of CO2 to be injected into storage at industrial rates in a reliable and secure manner, the operators of the project must also be able to demonstrate the accuracy of modelling predictions for storage to both the regulators and public. Leakage from storage will compromise both the capacity estimates of the storage capacity, and the perceived security of the project even if the leakage is transient. Fluid induced fractures caused by injection of CO2 above the fracture pressure of the formation will control the volume of CO2 a storage reservoir can hold, and will control the rate of CO2 injection; therefore the estimation of the pressure at which a formation will fracture is a key consideration in the modelling of a storage project. Field evidence of fracture pressures from reservoirs in the North Sea show evidence that the fracture pressure upon reinjection into a field is often lower than predicted by conventional approaches. This study presents a coupled geomechanical -fluid flow model modeling injection into a depleted field, the model exhibits hysteretic stress path behavior demonstrating a case of potential overestimation of fracture pressure. This study is the initial stage in a full sensitivity analysis of the material model parameters controlling stress path hysteresis including model geometry effects

Management of the Neck in Squamous Cell Carcinoma of the Oral Cavity and Oropharynx: ASCO Clinical Practice Guideline

PURPOSE:The aim of the current work is to provide evidence-based recommendations to practicing physicians and others on the management of the neck in patients with squamous cell carcinoma of the oral cavity and oropharynx. METHODS:ASCO convened an Expert Panel of medical oncology, surgery, radiation oncology, and advocacy experts to conduct a literature search, which included systematic reviews, meta-analyses, randomized controlled trials, and prospective and retrospective comparative observational studies published from 1990 through 2018. Outcomes of interest included survival, regional disease control, neck recurrence, and quality of life. Expert Panel members used available evidence and informal consensus to develop evidence-based guideline recommendations. RESULTS:The literature search identified 124 relevant studies to inform the evidence base for this guideline. Six clinical scenarios were devised; three for oral cavity cancer and three for oropharynx cancer, and recommendations were generated for each one. RECOMMENDATIONS:For oral cavity cancers, clinical scenarios focused on the indications for and the hallmarks of a high-quality neck dissection, indications for postoperative radiotherapy or chemoradiotherapy, and whether radiotherapy alone is sufficient elective treatment of an undissected neck compared with high-quality neck dissection. For oropharynx cancers, clinical scenarios focused on hallmarks of a high-quality neck dissection, factors that would favor operative versus nonoperative primary management, and clarifying criteria for an incomplete response to definitive chemoradiation for which salvage neck dissection would be recommended. Consensus was reached and recommendations were made for all six clinical scenarios. Additional information is available at www.asco.org/head-neck-cancer-guidelines