CS448 - Visualization

HW1 - Mike Cammarano

I have drawn both my examples from reports in Science magazine examining devices for quantum computing and communication.

Alas, I haven't got much domain-specific expertise regarding the phenomena presented. I have nevertheless attempted to summarize the background story of each image by largely syntactic manipulation of the original caption, paper abstract, and relevant portions of the body text.

Good: Figure 2 from Probing and Controlling the Bonds of an Artificial Molecule. A. W. Holleitner, R. H. Blick, A. K. Hüttel, K. Eberl, J. P. Kotthaus. Science, Vol. 297 No. 5578. Page 70. 5 July 2002. Story The paper examines electron-sharing behavior at an electronic junction based on a pair of coupled semiconductor quantum dots. More Detail >> The paper examines electron-sharing behavior at an electronic junction based on a pair of coupled semiconductor quantum dots. The paper explores how quantum states of a pair of coupled semiconductor quantum dots can be manipulated by varying the voltages of four neighboring electrodes. The quantum dots can each contain around 20 electrons, and their proximity to each other and to nearby electrodes allows electrons to be shared under certain circumstances. Two of the adjacent electrodes are identified as the source and drain, while the other two are the coupling electrodes used to manipulate the behavior of the dots. While the quantum state of the dots can't be directly measured, it can be indirectly probed by measuring the differential conductance between source and drain. This diagram examines the differential conductance from source to drain as a function of the voltages at the two coupling electrodes. Each hexagonal cell represents a charge configuration with n electrons on dot 1 and m electrons on dot 2. A major effect the graph is intended to illustrate is the pronounced resonance produced by the exchange of two electrons in the coupling between configurations (n,m) and (n-1,m-1). Critique I found this diagram particularly elegant, as it presents a substantial body of raw, measured data in an accessible way while making the underlying structure readily apparent. Without having to look at the caption, I was able to correctly infer many of the facts it is intended to convey: The main plot in part B shows a color-coded representation of a scalar function of two variables, with the parameters mapped to the axes. The plot in part A is a 1-D slice through the data corresponding to the dotted line in B. It gives a quantitative feel for the data and also elucidates the color-coding used in B. B makes the regularity and structure of the data trivially apparent, and directs the viewer's attention to the detail of this structure illustrated schematically in C. In short, the diagram tells no lies and refrains from simplifying the data, but still illustrates its structure in a clear and appealing way.

Bad: Figure 2.D from Atomic Memory for Correlated Photon States. C.H. van der Wal, M. D. Eisaman, A. André, R.L. Walsworth, D. F. Phillips, A. S. Zibrov, M. D. Lukin. Science, Vol. 301 No. 5630. Page 197. 11 July 2003. Story The paper examines a method for producing of a pair of quantum-mechanically correlated light pulses separated by a controllable delay. The emission of the Stokes photon is accompanied by a change in the spin-wave of an ensemble of rubidium atoms. The application of a second control beam (the retrieve beam) triggers the conversion of this spin state into a second light beam (the anti-Stokes) correlated with the first. The figure plots a theoretical simulation of an initial Stokes fluctuation propagating and evolving into an amplified pair of Stokes (red) and anti-Stokes (blue) light pulses with locked propagation. Critique While not terrible, there are several shortcomings to this diagram that make it fairly disappointing (at least in contrast to the high quality of technical illustration generally appearing in Science): The 3-dimensional stacking of the sub-plots makes comparing them with either the axes or each other unnecessarily difficult. The "distinct" red plots run into each other on the left side of the diagram and require effort to disambiguate. The gridding of the 3 reference planes introduces an unintended Necker cube illusion that may be bothersome for some viewers. As the idealized trend being illustrated is fairly simple, the graph poses needless visual complexity for its low information content.