Gravitational sensing with weak value based optical sensors

Using weak values amplification angular resolution limits, we theoretically investigate the gravitational sensing of objects. By inserting a force-sensing pendulum into a weak values interferometer, the optical response can sense accelerations to a few 10's of $\mathrm{zepto}\text{-}\mathrm{g}/\sqrt{\mathrm{Hz}}$, with optical powers of $1~\mathrm{mW}$. We convert this precision into range and mass sensitivity, focusing in detail on simple and torsion pendula. Various noise sources present are discussed, as well as the necessary cooling that should be applied to reach the desired levels of precision.Comment: 9 pages, 4 figures, Quantum Stud.: Math. Found. (2018

Linear control of the Pendubot over packet-drop networks

In this thesis we investigate control across stochastic drop-out channels. We seek optimal linear controllers for mean-square stability that make use of the knowledge of whether a packet is received. We establish a fundamental bound on drop-out probability allowable for stabilization, which in some cases is tight. When tight, a convex optimization provides controller design. The main result is a remote stabilization technique that always achieves this bound via acknowledgement from the actuation receiver. Controller information structure and decentralization issues are considered. The theory is then applied to the inverted pendulum experiment Pendubot. The Pendubot is a nonlinear plant that balances the links of an inverted pendulum via a control torque and optical sensors for position. A control strategy is developed using the stabilization technique derived above together with linearization and discretization of the apparatus. The complete design procedure is documented leading to a successful controller. Included are the encountered hardware issues, software issues in Matlab and C programming, theoretical issues, and experiment results. A mock drop-out network is simulated via C programming. The experiments validate that the theoretical design technique actually works, and that the theoretical bounds on allowable drop-out have significant practical bearing

Weak-value amplification and optimal parameter estimation in the presence of correlated noise

We analytically and numerically investigate the performance of weak-value amplification (WVA) and related parameter estimation methods in the presence of temporally correlated noise. WVA is a special instance of a general measurement strategy that involves sorting data into separate subsets based on the outcome of a second "partitioning" measurement. Using a simplified noise model that can be analyzed exactly together with optimal statistical estimators, we compare WVA to a conventional measurement method. We find that introducing WVA indeed yields a much lower variance of the parameter of interest than does the conventional technique, optimized in the absence of any partitioning measurements. In contrast, a statistically optimal analysis that employs partitioning measurements, incorporating all partitioned results and their known correlations, is found to yield an improvement -- typically slight -- over the noise reduction achieved by WVA. This is because the simple WVA technique is not tailored to a given noise environment and therefore does not make use of correlations between the different partitions. We also compare WVA to traditional background subtraction, a familiar technique where measurement outcomes are partitioned to eliminate unknown offsets or errors in calibration. Surprisingly, in our model background subtraction turns out to be a special case of the optimal partitioning approach in the balanced case, possessing a similar typically slight advantage over WVA. These results give deeper insight into the role of partitioning measurements, with or without post-selection, in enhancing measurement precision, which some have found puzzling. We finish by presenting numerical results to model a more realistic laboratory situation of time-decaying correlations, showing our conclusions hold for a wide range of statistical models.Comment: Revisions incorporate feedback from reviewer

Heisenberg scaling with weak measurement: A quantum state discrimination point of view

We examine the results of the paper "Precision metrology using weak measurements", [Zhang, Datta, and Walmsley, arXiv:1310.5302] from a quantum state discrimination point of view. The Heisenberg scaling of the photon number for the precision of the interaction parameter between coherent light and a spin one-half particle (or pseudo-spin) has a simple interpretation in terms of the interaction rotating the quantum state to an orthogonal one. In order to achieve this scaling, the information must be extracted from the spin rather than from the coherent state of light, limiting the applications of the method to phenomena such as cross-phase modulation. We next investigate the effect of dephasing noise, and show a rapid degradation of precision, in agreement with general results in the literature concerning Heisenberg scaling metrology. We also demonstrate that a von Neumann-type measurement interaction can display a similar effect.Comment: 7 pages, 3 figure

Artists Becoming Teachers: Expressions of Identity Transformation in a Virtual Forum

This article is an investigation of art and design graduates' identities as they embark upon their training as teachers. The expressive, 'confessional' nature of forum posts from their Virtual Learning Environment are analysed in relation to the students' identity transformation into teachers. This transition is profound in the case of artist teachers, for whom the contrast between their practice as a critical artist and that of a regulated professional can be severe. The usage of these socially-oriented virtual forums, and the students' identity transition is analysed in terms of identity theorists such as Butler, hooks and Wenger. There are problems of expression that are brought about by the juxtaposition of visually and spatially adept artist-learners constrained within a largely textual environment, yet this impediment appears to be ameliorated by their social-expressive exploitation of the forums

Finite size scaling of the correlation length above the upper critical dimension

We show numerically that correlation length at the critical point in the five-dimensional Ising model varies with system size L as L^{5/4}, rather than proportional to L as in standard finite size scaling (FSS) theory. Our results confirm a hypothesis that FSS expressions in dimension d greater than the upper critical dimension of 4 should have L replaced by L^{d/4} for cubic samples with periodic boundary conditions. We also investigate numerically the logarithmic corrections to FSS in d = 4.Comment: 5 pages, 6 postscript figure

The Impact of Prolonged Nomination Contests on Presidential Candidate Evaluations and General Election Vote Choice: The Case of 2008

The fact that political parties hold competitive nomination contests that require voters to choose among multiple candidates leaves open the possibility that the contest itself could damage the prospects of an eventual nominee. In this study, we employ the American National Election Study panel survey data from the 2008 U.S. presidential election to assess the impact of the Democratic Party nomination process on candidate evaluations and general election vote preference. We find evidence that Barack Obama had greater difficulty uniting his party than his Republican counterpart due to the fact that Clinton voters were slow to coalesce around Obama. These supporters failed to report higher levels of favorability until Clinton conceded the race in the summer, while Huckabee and Romney voters were seen rallying to their party\u27s nominee in the spring. In the end, many Clinton primary voters either abstained from voting in November or crossed over to support the Republican nominee