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Williams, C.

Publications and source records attributed to Williams, C..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Optimal design of two-qubit quantum circuits

In order to demonstrate non-trivial quantum computations experimentally, such as the synthesis of arbitrary entangled states, it will be useful to nderstand how to decompose a desired quantum computation into the shortest possible sequence of one-qubit and two-qubit gates. We contribute to this effort by providing a method to construct an optimal quantum circuit for a general two-qubit gate that requires at most 3 CNOT gates and 15 elementary one qubit gates. We then prove that these constructions are optimal with respect to the family of CNOT, y-rotation, z-rotation, and phase gates.

quantum circuit unitary operation↗
NASA NTRS2003

A novel model-based diagnosis engine: theory and applications

Systematic methods of general diagnosis exist in literature, but they all suffer from two major drawbacks that severely limit their practical applications. In this paper, we propose a two-fold approach to overcome these limitations.

diagnosis integer programming hitting set problem↗
NASA NTRS1999

Inlet Flow Distortion and Unsteady Blade Response in a Transonic Axial-Compressor Rotor

This paper describes the unsteady blade surface pressures on the first-stage rotor blades of a two-stage transonic axial flow compressor experiencing inlet flow distortion. This study was conducted to demonstrate the ability of a full annulus unsteady Reynolds-averaged Navier-Stokes numerical technique to predict unsteady pressures on the rotor blades operating in a distorted inflow. A total pressure distortion produced by a variable mesh screen mounted near the inlet was used to excite the unsteady blade loading on the rotor. On-blade pressure transducers were used to measure the unsteady blade surface pressure. These pressures and the resulting transient load on the rotor blades were compared to the numerical prediction. It is important to develop numerical techniques to predict these transient loads to better understand the response of compressor blades to forcing functions. With this enhanced understanding and ability to predict these transient forces, more robust compressors can be developed. In the study, a high definition of the inlet flow distortion was achieved by rotating the distortion screens. In this manner the inlet flow distortion and the distortion at the first stage stator leading edge were measured at approximately every 0.7 degrees. This full annulus high definition of the inlet flow distortion was used as the inlet boundary condition for the numerical technique. The experimental measurements and numerical analyses are highly complementary in this study. Detailed comparisons between the measurements and the numerical analyses indicate that the current numerical procedure calculates the unsteady aerodynamic pressure on the blade surfaces reasonably well. Further, the agreement of the measured and predicted rotor exit flow distortion at the first stage stator leading edge provides verification of the numerical technique.

Rabe, D. C.↗
NASA NTRS1999

Fast Quantum Algorithms for Numerical Integrals and Stochastic Processes

We discuss quantum algorithms that calculate numerical integrals and descriptive statistics of stochastic processes. With either of two distinct approaches, one obtains an exponential speed increase in comparison to the fastest known classical deterministic algotithms and a quadratic speed increase incomparison to classical Monte Carlo methods.

quantum algorithms numerical integrals↗
NASA NTRS1999

Quantum Algorithms

This thesis describes several new quantum algorithms. These include a polynomial time algorithm that uses a quantum fast Fourier transform to find eigenvalues and eigenvectors of a Hamiltonian operator, and that can be applied in cases for which all know classical algorithms require exponential time.

Quantum Algorithms polynomial time algorithm Hamil↗
NASA NTRS1999

Maxwell Duality, Lorentz Invariance, and Topological Phase

We discuss the Maxwell electromagnetic duality relations between the Aharonov-Bohm, Aharonov-Casher, and He-McKellar-Wilkens topological phases, which allows a unified description of all three phenomena.

Maxwell Duality Lorentz Invariance Topological Pha↗