UC Berkeley

Tensor network quantum machine learning (QML) models are promising applications on near-term quantum hardware. While decoherence of qubits is expected to decrease the performance of QML models, it is unclear to what extent the diminished performance can be compensated for by adding ancillas to the models and accordingly increasing the virtual bond dimension of the models. We investigate here the competition between decoherence and adding ancillas on the classification performance of two models, with an analysis of the decoherence effect from the perspective of regression. We present numerical evidence that the fully decohered unitary tree tensor network (TTN) with two ancillas performs at least as well as the non-decohered unitary TTN, suggesting that it is beneficial to add at least two ancillas to the unitary TTN regardless of the amount of decoherence may be consequently introduced.

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California’s water supplies are facing unprecedented stresses, and the state’s water-management systems are struggling to meet both environmental and human needs (agricultural, municipal, industrial). Supplies are highly vulnerable to climate variability and extreme events, limiting options to respond to the combined stresses of a changing climate, population, and land cover. Strategic, coordinated investments in California’s water infrastructure, institutions, and information will provide the foundation for a secure, equitable, and efficient water future. The cornerstone of water security, and priority need for California, is a modern, robust water-information system that enables accurate, timely, and transparent accounting through the water-supply and use cycle. This system must extend from mountain headwaters through valley groundwater. Investments are also needed in capacity building for use of water information among institutions and stakeholders across the state. Priority infrastructure improvements are needed for central elements of the state’s “green” infrastructure: restoration of Sierra Nevada and other forests in source-water areas, and additional groundwater recharge on farmland and expanded floodplains. With better-informed management, California’s existing water supplies could go further to meeting the state’s urban, agricultural, ecological, and industrial needs.

This paper explores the role of international partnerships to facilitate low-energy building design, construction, and operations. We present the strategic approach, joint research and development outcomes, and implementation activities of a unique U.S.-India program on buildings energy efficiency, the Center for Building Energy Research and Development. We discuss the collaboration successes in both countries despite their dissimilar building contexts, implementation challenges and opportunities. We highlight a range of R&D outcomes, such as novel tools and technologies developed and tested by the joint teams, with their technical energy savings potential, as well as results of capacity building and technology demonstrations. A deep-dive into key new scientific methods around building energy monitoring and benchmarking that could have a significant impact on high-performanceof buildings in both countries is also provided. Finally, in addition to joint R&D successes, pathways to deployment, and lessons learned are discussed as key takeaways.

AbstractNiche environmental conditions influence both the structure and function of microbial communities and the cellular function of individual strains. The terrestrial subsurface is a dynamic and diverse environment that exhibits specific biogeochemical conditions associated with depth, resulting in distinct environmental niches. Here, we present the characterization of seven distinct strains belonging to the genus Arthrobacter isolated from varying depths of a single sediment core and associated groundwater from an adjacent well. We characterized genotype and phenotype of each isolate to connect specific cellular functions and metabolisms to ecotype. Arthrobacter isolates from each ecotype demonstrated functional and genomic capacities specific to their biogeochemical conditions of origin, including laboratory-demonstrated characterization of salinity tolerance and optimal pH, and genes for utilization of carbohydrates and other carbon substrates. Analysis of the Arthrobacter pangenome revealed that it is notably open with a volatile accessory genome compared to previous pangenome studies on other genera, suggesting a high potential for adaptability to environmental niches.