Image recognition with an adiabatic quantum computer I. Mapping to quadratic unconstrained binary optimization

Many artificial intelligence (AI) problems naturally map to NP-hard optimization problems. This has the interesting consequence that enabling human-level capability in machines often requires systems that can handle formally intractable problems. This issue can sometimes (but possibly not always) be resolved by building special-purpose heuristic algorithms, tailored to the problem in question. Because of the continued difficulties in automating certain tasks that are natural for humans, there remains a strong motivation for AI researchers to investigate and apply new algorithms and techniques to hard AI problems. Recently a novel class of relevant algorithms that require quantum mechanical hardware have been proposed. These algorithms, referred to as quantum adiabatic algorithms, represent a new approach to designing both complete and heuristic solvers for NP-hard optimization problems. In this work we describe how to formulate image recognition, which is a canonical NP-hard AI problem, as a Quadratic Unconstrained Binary Optimization (QUBO) problem. The QUBO format corresponds to the input format required for D-Wave superconducting adiabatic quantum computing (AQC) processors.Comment: 7 pages, 3 figure

For Fixed Control Parameters the Quantum Approximate Optimization Algorithm's Objective Function Value Concentrates for Typical Instances

The Quantum Approximate Optimization Algorithm, QAOA, uses a shallow depth quantum circuit to produce a parameter dependent state. For a given combinatorial optimization problem instance, the quantum expectation of the associated cost function is the parameter dependent objective function of the QAOA. We demonstrate that if the parameters are fixed and the instance comes from a reasonable distribution then the objective function value is concentrated in the sense that typical instances have (nearly) the same value of the objective function. This applies not just for optimal parameters as the whole landscape is instance independent. We can prove this is true for low depth quantum circuits for instances of MaxCut on large 3-regular graphs. Our results generalize beyond this example. We support the arguments with numerical examples that show remarkable concentration. For higher depth circuits the numerics also show concentration and we argue for this using the Law of Large Numbers. We also observe by simulation that if we find parameters which result in good performance at say 10 bits these same parameters result in good performance at say 24 bits. These findings suggest ways to run the QAOA that reduce or eliminate the use of the outer loop optimization and may allow us to find good solutions with fewer calls to the quantum computer.Comment: 16 pages, 1 figur

Nonlinear Time-Domain Analysis of a Sliding Block on a Plane

A time domain finite difference numerical model of a sliding rigid block on a plane is developed using a simple elastic-perfectly plas-tic Mohr-Coulomb interface model. The model is shown to accurately predict the slip-stick and slip-slip behavior deduced from an analytical solution for behavior of a sliding block on a horizontal plane and the results of physical model tests of a block on both hori-zontal and inclined planes subject to harmonic and non-uniform excitation provided the appropriate interface strength is employed. Back analyses of the physical model tests show that for some geosynthetic interfaces, the interface shear strength depends upon the velocity of sliding. The numerical model developed herein provides a basis for rigorous evaluation of several important problems in geotechnical earthquake engineering, including the cumulative permanent seismic deformation of landfills, embankments, slopes, and retaining walls and the stresses induced by seismic loading in geosynthetic elements of landfill liner and cover systems

Frequency-comb-induced radiative force on cold rubidium atoms

We experimentally investigate the radiative force and laser-induced fluorescence (LIF) in cold rubidium atoms induced by pulse-train (frequency-comb) excitation. Three configurations are studied: (i) single-pulse-train excitation, (ii) two in-phase counterpropagating pulse trains, and (iii) two out-of-phase counterpropagating pulse trains. In all configurations, measured LIF is in agreement with calculations based on the optical Bloch equations. The observed forces in the first two configurations are in qualitative agreement with the model(s) used for calculating mechanical action of a pulse train on atoms; however, this is not the case for the third configuration. Possible resolution of the discrepancy is discussed

Optimization of a wind powered desalination and pumped hydro storage system

The penetration of intermittent renewable energy sources, for instances wind power, in the power system of isolated islands is limited, even when there is large potential. The wind power that cannot be directly injected in the power grid is usually curtailed. In addition, some islands need to desalinate seawater to produce fresh water, increasing the pressure on the power system, because desalination needs electricity. Nevertheless, the water scarcity problem of an island can be part of the solution of the problem of its integration of intermittent renewable energy sources. To tackle this issue, a system was proposed to use the excess wind power in desalination units and in a pumped hydro storage, resulting in an integrated power and water supply system that would minimize the wind power curtailed. This paper proposes a methodology to optimize the size and operational strategy of this wind powered desalination and pumped hydro storage system. The objective is to minimize the total annualized production costs, maximize the percentage of renewable energy sources in the total power production and minimize the wind power curtailed. To solve this optimization problem, a derivative free multiobjective optimization method (Direct MultiSearch) is used. This methodology is applied to the integrated power and water supply system proposed for the island of S. Vicente, in Cape Verde. The results show that the penetration of renewable energy sources can reach 84% with a 27% decrease of power and water production costs and 67% decrease of CO2 emissions, in relation to the values foreseen for 2020.info:eu-repo/semantics/publishedVersio