Proposed Measurement Scheme Research Articles

Mutual information-based approach to adaptive homodyne detection of quantum optical states

The author proposes an approach to adaptive homodyne detection of digitally modulated quantum optical pulses in which the phase of the local oscillator is chosen to maximize the average information gain, i.e., the mutual information, at each step of the measurement. The properties of this adaptive detection scheme are studied by considering the problem of classical information content of ensembles of coherent states. Simulations of quantum trajectories and visualizations of corresponding measurement operators demonstrate that the proposed measurement scheme adapts itself to the features of each ensemble. For all considered ensembles of coherent states, it consistently outperforms heterodyne detection and Wiseman's adaptive scheme for phase measurements [H.M. Wiseman, Phys. Rev. Lett. 75, 4587 (1995)].

Measurement Scheme Synthesis in Multi-Station Machining Systems

Different sets of measurements carry different amounts of information about the root causes of quality problems in machining. The selection of measurements in multi-station machining systems is currently a slow and error-prone process based on expert human knowledge. In this paper, we propose systematic procedures for synthesizing measurement schemes that carry the most information about the root causes of dimensional machining errors. The amount of root cause information conveyed by a given set of measurements was assessed using the recently introduced formal methods for quantitative characterization of measurement schemes in multi-station machining systems. The newly proposed measurement scheme synthesis procedures were applied to devising measurement schemes in an automotive cylinder head machining process. It was observed that the measurement scheme synthesis procedure based on a genetic algorithm robustly outperformed the synthesis procedures based on the heuristics of successive measurement removal.

Purity of Gaussian states: Measurement schemes and time evolution in noisy channels

We present a systematic study of the purity for Gaussian states of single-mode continuous variable systems. We prove the connection of purity to observable quantities for these states, and show that the joint measurement of two conjugate quadratures is necessary and sufficient to determine the purity at any time. The statistical reliability and the range of applicability of the proposed measurement scheme are tested by means of Monte Carlo simulated experiments. We then consider the dynamics of purity in noisy channels. We derive an evolution equation for the purity of general Gaussian states both in thermal and in squeezed thermal baths. We show that purity is maximized at any given time for an initial coherent state evolving in a thermal bath, or for an initial squeezed state evolving in a squeezed thermal bath whose asymptotic squeezing is orthogonal to that of the input state.

Measurement and State Preparation via Ion Trap Quantum Computing

We investigate in detail the effects of a QND vibrational number measurement made on single ions in a recently proposed measurement scheme for the vibrational state of a register of ions in a linear rf trap [C. D'Helon and G. J. Milburn, phys. Rev. A 54, 5141 (1996)]. The performance of a measurement shows some interesting patterns which are closely related to searching.

Printed Chinese Character Similarity Measurement Using Ring Projection and Distance Transform

This paper presents a new Chinese character similarity measurement method based on the ring projection algorithm and distance transform. The ring projection algorithm is used to transform a character image with two independent variables into a function of one independent variable in the ring projection space. This representation of character in the ring projection space has been proved to be in orientation and scale invariant. However, this representation will be distorted nonlinearly in the presence of noise. Therefore, common linear metrics such as Euclidean distance, cannot be applied to measure distance. To solve the nonlinear distortion problem, distance transform is proposed as a nonlinear metric. The similarity measurement is performed using the distance transformed image in the ring projection space. A number of Chinese characters are selected to evaluate the capability of the proposed measurement scheme and the results are encouraging.

Collapses and Revivals of Bose-Einstein Condensates Formed in Small Atomic Samples.

The macroscopic wave function for atomic samples composed of a few thousand particles is shown to exhibit collapses and revivals on a few seconds time scale, while Bose-Einstein condensation remains in the form of off-diagonal long-range order in the one-particle reduced density matrix. A recently proposed measurement scheme which is sensitive to Bose-broken gauge symmetry, and hence to the macroscopic wave function, could be used to detect the collapses and revivals experimentally.

Mechanical Parameter Measurement of 2-Mass Resonant System Using Disturbance Observer.

In application fields of a 2-mass resonant system, control theory-based various techniques by using feedforward/feedback control have been proposed to achieve the high performance motion control. Although these schemes are effective to suppress the resonant vibration, they are quite sensitive to system parameters because the design of such controllers basically relies on system mechanical parameters.This paper presents a disturbance observer-based novel mechanical parameter measurement scheme of 2-mass resonant system. In the proposed measurement, the load inertia and the torsional constant of the resonant system can be measured by using error components of the estimated disturbance torque due to setting errors of the parameters in the observer. This measurement algorithm has a distinctive feature that no additional tool but the observer is required for the parameter measurement. The effectiveness of the proposed measurement scheme is verified by experimental results which are obtained by a prototype.

Low-gravity propellant gauging system for accurate predictions of spacecraft end-of-life

This paper describes a low-gravity propellant gauging system (PGS) developed, tested, and patented at Hughes Aircraft Company. The PGS predicts spacecraft end of life (EOL) within ± 2 months or better at midlife for a 15-year nominal mission and is used in the Hughes HS601 geosynchronous communications satellites. The PGS is conceptually simple and strives to minimize hardware required for implementation. It incorporates high-resolution pressure transducers and interconnect valves between existing pressurant and propellant tanks. The PGS employs periodic repressurization of propellant tanks by momentary opening of the interconnect valve between the relatively higher pressure pressurant tank and the propellant tank. Measurements of pressures before and after repressurization allow the determination of gas volume in the propellant tank through gas-law calculations, which in turn yields liquid volume, and hence propellant mass within the tank. The use of the gas law also requires temperature measurements, tor accurate temperature measurement, multiple temperature sensors are employed in each tank, and to enhance further the accuracy, extremely accurate and high-resolution pressure transducers are used as gas thermometers. Prototype testing of the proposed measurement scheme has established confidence in the system's ability to predict spacecraft EOL accurately due to propellant depletion. The PGS is failure-toler ant and does not interfere with normal operation of the propulsion subsystem. The repressurizatioh capability offers an additional advantage of closely controlling the oxidizer-to-fuel-mixture ratio in a bipropellant propulsion system. This, in turn, increases the stationkeeping life by minimizing the propellant residuals associated With depletion of one propellant species before the other.

Elimination of Source A and B Errors in p‐Median Location Problems

The p‐median problem is a powerful tool in analyzing facility location options when the goal of the location scheme is to minimize the average distance that demand must traverse to reach its nearest facility. It may be used to determine the number of facilities to site, as well as the actual facility locations. Demand data are frequently aggregated in p‐median location problems to reduce the computational complexity of the problem. Demand data aggregation, however, results in the loss of locational information. This loss may lead to suboptimal facility location configurations (optimality errors) and inaccurate measures of the resulting travel distances (cost errors). Hillsman and Rhoda (1978) have identified three error components: Source A, B, and C errors, which may result from demand data aggregation. In this article, a method to measure weighted travel distances in p‐median problems which eliminates Source A and B errors is proposed. Test problem results indicate that the proposed measurement scheme yields solutions with lower optimality and cost errors than does the traditional distance measurement scheme.