An Open-System Quantum Simulator with Trapped Ions

The control of quantum systems is of fundamental scientific interest and promises powerful applications and technologies. Impressive progress has been achieved in isolating the systems from the environment and coherently controlling their dynamics, as demonstrated by the creation and manipulation of entanglement in various physical systems. However, for open quantum systems, engineering the dynamics of many particles by a controlled coupling to an environment remains largely unexplored. Here we report the first realization of a toolbox for simulating an open quantum system with up to five qubits. Using a quantum computing architecture with trapped ions, we combine multi-qubit gates with optical pumping to implement coherent operations and dissipative processes. We illustrate this engineering by the dissipative preparation of entangled states, the simulation of coherent many-body spin interactions and the quantum non-demolition measurement of multi-qubit observables. By adding controlled dissipation to coherent operations, this work offers novel prospects for open-system quantum simulation and computation.Comment: Pre-review submission to Nature. For an updated and final version see publication. Manuscript + Supplementary Informatio

Dust outpaces bedrock in nutrient supply to montane forest ecosystems.

Dust provides ecosystem-sustaining nutrients to landscapes underlain by intensively weathered soils. Here we show that dust may also be crucial in montane forest ecosystems, dominating nutrient budgets despite continuous replacement of depleted soils with fresh bedrock via erosion. Strontium and neodymium isotopes in modern dust show that Asian sources contribute 18-45% of dust deposition across our Sierra Nevada, California study sites. The remaining dust originates regionally from the nearby Central Valley. Measured dust fluxes are greater than or equal to modern erosional outputs from hillslopes to channels, and account for 10-20% of estimated millennial-average inputs of bedrock P. Our results demonstrate that exogenic dust can drive the evolution of nutrient budgets in montane ecosystems, with implications for predicting forest response to changes in climate and land use

Dust outpaces bedrock in nutrient supply to montane forest ecosystems.

Dust provides ecosystem-sustaining nutrients to landscapes underlain by intensively weathered soils. Here we show that dust may also be crucial in montane forest ecosystems, dominating nutrient budgets despite continuous replacement of depleted soils with fresh bedrock via erosion. Strontium and neodymium isotopes in modern dust show that Asian sources contribute 18-45% of dust deposition across our Sierra Nevada, California study sites. The remaining dust originates regionally from the nearby Central Valley. Measured dust fluxes are greater than or equal to modern erosional outputs from hillslopes to channels, and account for 10-20% of estimated millennial-average inputs of bedrock P. Our results demonstrate that exogenic dust can drive the evolution of nutrient budgets in montane ecosystems, with implications for predicting forest response to changes in climate and land use

Climatic control of denudation in the deglaciated landscape of the Washington cascades

Since the Last Glacial Maximum, the extent of glaciers in many mountainous regions has declined, and erosion driven by glacial processes has been supplanted by fluvial incision and mass wasting processes. This shift in the drivers of erosion is thought to have altered the rate and pattern of denudation of these landscapes. The Washington Cascades Mountains in the northwestern USA still bear the topographic imprint of Pleistocene glaciations, and are affected by large variations in precipitation, making them an ideal setting to assess the relative controls of denudation. Here we show that denudation rates over the past millennia, as determined by 10Be exposure ages, range from 0.08 to 0.57 mm yr−1, about four times higher than the rates inferred for million-year timescales. We find that the millennial timescale denudation rates increase linearly with modern precipitation rates. Based on our landscape analyses, we suggest that this relationship arises because intense precipitation triggers landslides, particularly on slopes that have been steepened by glacial erosion before or during the Last Glacial Maximum. We conclude that the high modern interglacial denudation rates we observe in the Washington Cascades are driven by a disequilibrium between the inherited topography and the current spatial distribution of erosional processes that makes this range particularly sensitive to spatial variations in climate

Chemical weathering in active mountain belts controlled by stochastic bedrock landsliding

International audienceA link between chemical weathering and physical erosion exists at the catchment scale over a wide range of erosion rates1,2. However, in mountain environments, where erosion rates are highest, weathering may be kinetically limited3,4,5 and therefore decoupled from erosion. In active mountain belts, erosion is driven by bedrock landsliding6 at rates that depend strongly on the occurrence of extreme rainfall or seismicity7. Although landslides affect only a small proportion of the landscape, bedrock landsliding can promote the collection and slow percolation of surface runoff in highly fragmented rock debris and create favourable conditions for weathering. Here we show from analysis of surface water chemistry in the Southern Alps of New Zealand that weathering in bedrock landslides controls the variability in solute load of these mountain rivers. We find that systematic patterns in surface water chemistry are strongly associated with landslide occurrence at scales from a single hillslope to an entire mountain belt, and that landslides boost weathering rates and river solute loads over decades. We conclude that landslides couple erosion and weathering in fast-eroding uplands and, thus, mountain weathering is a stochastic process that is sensitive to climatic and tectonic controls on mass wasting processes