The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform

H Bombin - One of the best experts on this subject based on the ideXlab platform.

  • self correcting quantum computers
    New Journal of Physics, 2013
    Co-Authors: H Bombin, R W Chhajlany, Michal Horodecki, M A Martindelgado
    Abstract:

    Is the notion of a quantum computer (QC) resilient to thermal noise unphysical? We address this question from a constructive perspective and show that local quantum Hamiltonian models provide self-correcting QCs. To this end, we first give a sufficient condition on the connectedness of excitations for a stabilizer code model to be a self-correcting quantum memory. We then study the two main examples of topological stabilizer codes in arbitrary dimensions and establish their self-correcting capabilities. Also, we address the transversality properties of topological color codes, showing that six-dimensional color codes provide a self-correcting model that allows the transversal and local implementation of a universal set of operations in seven spatial dimensions. Finally, we give a procedure for initializing such quantum memories at finite temperature.

  • self correcting quantum computers
    arXiv: Quantum Physics, 2009
    Co-Authors: H Bombin, R W Chhajlany, Michal Horodecki, M A Martindelgado
    Abstract:

    Is the notion of a quantum computer resilient to thermal noise unphysical? We address this question from a constructive perspective and show that local quantum Hamiltonian models provide self-correcting quantum computers. To this end, we first give a sufficient condition on the connect- edness of excitations for a stabilizer code model to be a self-correcting quantum memory. We then study the two main examples of topological stabilizer codes in arbitrary dimensions and establish their self-correcting capabilities. Also, we address the transversality properties of topological color codes, showing that 6D color codes provide a self-correcting model that allows the transversal and local implementation of a universal set of operations in seven spatial dimensions. Finally, we give a procedure to initialize such quantum memories at finite temperature.

M A Martindelgado - One of the best experts on this subject based on the ideXlab platform.

  • self correcting quantum computers
    New Journal of Physics, 2013
    Co-Authors: H Bombin, R W Chhajlany, Michal Horodecki, M A Martindelgado
    Abstract:

    Is the notion of a quantum computer (QC) resilient to thermal noise unphysical? We address this question from a constructive perspective and show that local quantum Hamiltonian models provide self-correcting QCs. To this end, we first give a sufficient condition on the connectedness of excitations for a stabilizer code model to be a self-correcting quantum memory. We then study the two main examples of topological stabilizer codes in arbitrary dimensions and establish their self-correcting capabilities. Also, we address the transversality properties of topological color codes, showing that six-dimensional color codes provide a self-correcting model that allows the transversal and local implementation of a universal set of operations in seven spatial dimensions. Finally, we give a procedure for initializing such quantum memories at finite temperature.

  • self correcting quantum computers
    arXiv: Quantum Physics, 2009
    Co-Authors: H Bombin, R W Chhajlany, Michal Horodecki, M A Martindelgado
    Abstract:

    Is the notion of a quantum computer resilient to thermal noise unphysical? We address this question from a constructive perspective and show that local quantum Hamiltonian models provide self-correcting quantum computers. To this end, we first give a sufficient condition on the connect- edness of excitations for a stabilizer code model to be a self-correcting quantum memory. We then study the two main examples of topological stabilizer codes in arbitrary dimensions and establish their self-correcting capabilities. Also, we address the transversality properties of topological color codes, showing that 6D color codes provide a self-correcting model that allows the transversal and local implementation of a universal set of operations in seven spatial dimensions. Finally, we give a procedure to initialize such quantum memories at finite temperature.

Roger Wattenhofer - One of the best experts on this subject based on the ideXlab platform.

  • space complexity of streaming algorithms on universal quantum computers
    Theory and Applications of Models of Computation, 2020
    Co-Authors: Darya Melnyk, Yuyi Wang, Roger Wattenhofer
    Abstract:

    Universal quantum computers are the only general purpose quantum computers known that can be implemented as of today. These computers consist of a classical memory component which controls the quantum memory. In this paper, the space complexity of some data stream problems, such as PartialMOD and Equality, is investigated on universal quantum computers. The quantum algorithms for these problems are believed to outperform their classical counterparts. Universal quantum computers, however, need classical bits for controlling quantum gates in addition to qubits. Our analysis shows that the number of classical bits used in quantum algorithms is equal to or even larger than that of classical bits used in corresponding classical algorithms. These results suggest that there is no advantage of implementing certain data stream problems on universal quantum computers instead of classical computers when space complexity is considered.

Karl Whela - One of the best experts on this subject based on the ideXlab platform.

  • computers obsolescence and productivity
    The Review of Economics and Statistics, 2002
    Co-Authors: Karl Whela
    Abstract:

    This paper develops a new technique for measuring the effect of computer usage on U.S. productivity growth. Standard National Income and Product Accounts (NIPA) measures of the computer capital stock, which are constructed by weighting past investments according to a schedule for economic depreciation (the rate at which capital loses value as it ages), are shown to be inappropriate for growth accounting because they do not capture the effect of a unit of computer capital on productivity. This is due to technological obsolescence: machines that are still productive are retired because they are no longer near the technological frontier, and anticipation of retirement affects economic depreciation. Using a model that incorporates obsolescence, alternative stocks are developed that imply a larger computer-usage effect. This effect, together with the direct effect of increased productivity in the computer-producing sector, accounted for the improvement in U.S. productivity growth over 1996-1998 relative to the previous twenty years. © 2002 by the President and Fellows of Harvard College and the Massachusetts Institute of Technology

  • computers obsolescence and productivity
    Social Science Research Network, 2000
    Co-Authors: Karl Whela
    Abstract:

    This paper examines the role that computers have played in boosting U.S. economic growth in recent years. The paper focuses on two effects--the effect of increased productivity in the computer-producing sector and the effect of investments in computing equipment on the productivity of those who use them--and concludes that together they account for almost all of the recent acceleration in U.S. labor productivity. In calculating the computer-usage effect, standard NIPA measures of the capital stock are inappropriate for growth accounting because they do not account for technological obsolescence; this occurs when a machine that is still productive is retired because it is no longer near the technological frontier. Using a theoretical framework that explicitly accounts for technological obsolescence, alternative estimates of the computer capital stock are developed that imply larger effects on growth of computer capital accumulation than are suggested by the NIPA stocks.

Coughlan Damian - One of the best experts on this subject based on the ideXlab platform.

  • Repurposing end of life notebook computers from consumer WEEE as thin client computers – a hybrid end of life strategy for the circular economy in electronics
    'Glucksman Library University of Limerick', 2018
    Co-Authors: Coughlan Damian
    Abstract:

    peer-reviewedThis PhD thesis presents an investigation into the feasibility of repurposing endof- life notebook computers as thin client computers. Repurposing is the identification of a new use for a product that can no longer be used in its original form and has the potential to become a hybrid re-use/recycling end-of-life strategy for suitable e-waste when direct reuse is not economically or technically feasible. In this instance, it was targeted to produce thin client computers using motherboards, processors and memory from used laptops while recycling all other components. Notebook computers are of interest for this type of strategy due to having a large environmental impact in manufacturing but often not having the option of direct reuse as they are prone to damage and experience a rapid loss of value over time. They also contain multiple critical raw materials with very low recycling rates. The notebook computers were sourced from Civic Amenity sites (CA) and originated from business-to-consumer (B2C) channels. A total of 246 notebook computers were collected and analysed. The paper outlines a methodology developed to identify, test, analyse, and dismantle suitable devices for repurposing. The steps undertaken were 1) Visual inspection, 2) Power-on test 3) Initialstage Functionality test, 4) Dismantling, 5) Post-dismantling testing, 6) Finalstage Functionality testing. The results from the developed methodology indicated that 9% of the notebook computers were suitable for repurposing as thin client computers. It recommends the following design changes to laptops that would support repurposing; 1) PCB mounted Fan and Heatsink assembly, 2) Eliminate daughter and I/O boards, 3) A separate Power Button assembly, 4) Reduction in size of the motherboard’s physical footprint. A streamlined lifecycle analysis based on Cumulative Energy Demand (CED) was undertaken to compare the impact of repurposed notebook computers with new thin client computers. The results indicated that there are significant potential savings to be made by extending lifetimes and offsetting the production of new thin client computers under a range of assumptions

  • Repurposing end of life notebook computers from consumer WEEE as thin client computers – a hybrid end of life strategy for the circular economy in electronics
    University of Limerick, 2018
    Co-Authors: Coughlan Damian
    Abstract:

    This PhD thesis presents an investigation into the feasibility of repurposing endof- life notebook computers as thin client computers. Repurposing is the identification of a new use for a product that can no longer be used in its original form and has the potential to become a hybrid re-use/recycling end-of-life strategy for suitable e-waste when direct reuse is not economically or technically feasible. In this instance, it was targeted to produce thin client computers using motherboards, processors and memory from used laptops while recycling all other components. Notebook computers are of interest for this type of strategy due to having a large environmental impact in manufacturing but often not having the option of direct reuse as they are prone to damage and experience a rapid loss of value over time. They also contain multiple critical raw materials with very low recycling rates. The notebook computers were sourced from Civic Amenity sites (CA) and originated from business-to-consumer (B2C) channels. A total of 246 notebook computers were collected and analysed. The paper outlines a methodology developed to identify, test, analyse, and dismantle suitable devices for repurposing. The steps undertaken were 1) Visual inspection, 2) Power-on test 3) Initialstage Functionality test, 4) Dismantling, 5) Post-dismantling testing, 6) Finalstage Functionality testing. The results from the developed methodology indicated that 9% of the notebook computers were suitable for repurposing as thin client computers. It recommends the following design changes to laptops that would support repurposing; 1) PCB mounted Fan and Heatsink assembly, 2) Eliminate daughter and I/O boards, 3) A separate Power Button assembly, 4) Reduction in size of the motherboard’s physical footprint. A streamlined lifecycle analysis based on Cumulative Energy Demand (CED) was undertaken to compare the impact of repurposed notebook computers with new thin client computers. The results indicated that there are significant potential savings to be made by extending lifetimes and offsetting the production of new thin client computers under a range of assumptions