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327 results on '"Joshi, Manoj"'

11. Exploring Large-Scale Entanglement in Quantum Simulation

Author

Joshi, Manoj K., Kokail, Christian, van Bijnen, Rick, Kranzl, Florian, Zache, Torsten V., Blatt, Rainer, Roos, Christian F., and Zoller, Peter

Subjects
Quantum Physics
Abstract

Entanglement is a distinguishing feature of quantum many-body systems, and uncovering the entanglement structure for large particle numbers in quantum simulation experiments is a fundamental challenge in quantum information science. Here we perform experimental investigations of entanglement based on the entanglement Hamiltonian, as an effective description of the reduced density operator for large subsystems. We prepare ground and excited states of a 1D XXZ Heisenberg chain on a 51-ion programmable quantum simulator and perform sample-efficient `learning' of the entanglement Hamiltonian for subsystems of up to 20 lattice sites. Our experiments provide compelling evidence for a local structure of the entanglement Hamiltonian. This observation marks the first instance of confirming the fundamental predictions of quantum field theory by Bisognano and Wichmann, adapted to lattice models that represent correlated quantum matter. The reduced state takes the form of a Gibbs ensemble, with a spatially-varying temperature profile as a signature of entanglement. Our results also show the transition from area to volume-law scaling of Von Neumann entanglement entropies from ground to excited states. As we venture towards achieving quantum advantage, we anticipate that our findings and methods have wide-ranging applicability to revealing and understanding entanglement in many-body problems with local interactions including higher spatial dimensions., Comment: 14 pages, 7 figures

Published
2023
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32. Quantifying exposure biases in early instrumental land surface air temperature observations.

Author

Wallis, Emily J., Osborn, Timothy J., Taylor, Michael, Jones, Philip D., Joshi, Manoj, and Hawkins, Ed

Subjects
LAND surface temperature, ATMOSPHERIC temperature, SOLAR radiation, GRID cells
Abstract

Exposure biases are a pervasive non‐climatic change in land air temperature records which have been introduced as a result of changes in the way thermometers were sheltered from solar radiation and the elements over time. Exposure biases have not been widely accounted for in observational records, due to difficulties detecting/correcting the bias using traditional homogenisation techniques; therefore, exposure biases still contribute significant uncertainty to the early period in global temperature compilations. Here, an empirical approach to address the bias arising from the introduction of Stevenson‐type screens from the late‐19th century is presented. The approach consists of: (1) an empirical analysis of 54 parallel measurement series to identify the characteristics of the exposure bias in four exposure classes; (2) the development of bias‐estimation models based on an analysis of which variables influence the bias; and (3) the application of the models to an extended version of CRUTEM5 (CRUTEM5_ext), based on exposure metadata, to quantify and reduce the bias. Step one identified differences between the temperatures recorded in Stevenson screens and early exposures, which vary seasonally, diurnally, and with location and exposure class. The largest biases (in mean temperatures) were found in freestanding exposures (up to −0.78°C annually) and in summer, while the smallest biases were generally found in wall‐mounted exposures (near‐0°C annually) and in winter. Significant relationships between the bias and temperature, downward top of atmosphere and/or received shortwave downward solar radiation were found in each exposure class and led to the development of three regression‐based bias‐estimation models. Application of these models to 1,960 mid‐latitude stations in CRUTEM5_ext, resulted in small (≤0.016°C) positive adjustments to the Northern Hemisphere mid‐latitude mean before 1880, and larger (≤−0.1°C) negative adjustments to the Northern and Southern Hemisphere mid‐latitude means between 1882–1934 and 1856–1900, respectively. Larger adjustments were estimated regionally: up to −0.57°C annually and −0.79°C seasonally in individual grid cells. [ABSTRACT FROM AUTHOR]

Published
2024
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36. BoBBLE : Ocean—Atmosphere Interaction and Its Impact on the South Asian Monsoon

Author

Vinayachandran, P. N., Matthews, Adrian J., Kumar, K. Vijay, Sanchez-FrankNKs, Alejandra, Thushara, V., George, Jenson, Vijith, V., Webber, Benjamin G. M., Queste, Bastien Y., Roy, Rajdeep, Sarkar, Amit, Baranowski, Dariusz B., Bhat, G. S., Klingman, Nicholas P., Peatman, Simon C., Parida, C., Heywood, Karen J., Hall, Robert, King, Brian, Kent, Elizabeth C., Nayak, Anoop A., Neema, C. P., Amol, P., Lotliker, A., Kankonkar, A., Gracias, D. G., Vernekar, S., D’Souza, A. C., Valluvan, G., Pargaonkar, Shrikant M., Dinesh, K., Giddings, Jack, and Joshi, Manoj

Published
2018

44. Constraining an eddy energy dissipation rate due to relative wind stress for use in energy budget-based eddy parameterisations.

Author

Wilder, Thomas, Zhai, Xiaoming, Munday, David, and Joshi, Manoj

Subjects
ENERGY budget (Geophysics), CLIMATE change models, ENERGY dissipation, GENERAL circulation model, ENERGY consumption, EDDIES
Abstract

A geostrophic eddy energy dissipation rate due to the interaction of the large-scale wind field and mesoscale ocean currents, or relative wind stress, is derived here for use in eddy energy budget-based eddy parameterisations. We begin this work by analytically deriving a relative wind stress damping term and a baroclinic geostrophic eddy energy equation. The time evolution of this analytical eddy energy in response to relative wind stress damping is compared directly with a baroclinic eddy in a general circulation model for both anticyclones and cyclones. The dissipation of eddy energy is comparable between each model and eddy type, although the numerical model diverges from the analytical model at around day 150, likely due to the presence of non-linear baroclinic processes. A constrained dissipation rate due to relative wind stress is then proposed using terms from the analytical eddy energy budget. This dissipation rate depends on the potential energy of the eddy thermocline displacement, which also depends on eddy length scale. Using an array of ocean datasets, and computing two forms for the eddy length scale, a range of values for the dissipation rate are presented. The analytical dissipation rate is found to vary from 0.25 to 4 times that of a constant dissipation rate employed in previous studies. The dissipation rates are generally enhanced in the Southern Ocean but smaller in the western boundaries. This proposed dissipation rate offers a tool to parameterise the damping of total eddy energy in coarse resolution global climate models and may have implications for a wide range of climate processes. [ABSTRACT FROM AUTHOR]

Published
2023
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