Precision laser range finder system design for Advanced Technology Laboratory applications

Preliminary system design of a pulsed precision ruby laser rangefinder system is presented which has a potential range resolution of 0.4 cm when atmospheric effects are negligible. The system being proposed for flight testing on the advanced technology laboratory (ATL) consists of a modelocked ruby laser transmitter, course and vernier rangefinder receivers, optical beacon retroreflector tracking system, and a network of ATL tracking retroreflectors. Performance calculations indicate that spacecraft to ground ranging accuracies of 1 to 2 cm are possible

Band structure analysis of the conduction-band mass anisotropy in 6H and 4H SiC

The band structures of 6H and 4H SiC calculated by means of the FP-LMTO method are used to determine the effective mass tensors for their conduction-band minima. The results are shown to be consistent with recent optically detected cyclotron resonance measurements and predict an unusual band filling dependence for 6H-SiC.Comment: 5 pages including 4 postscript figures incorporated with epsfig figs. available as part 2: sicfig.uu self-extracting file to appear in Phys. Rev. B: Aug. 15 (Rapid Communications

Voltage Control of Exchange Coupling in Phosphorus Doped Silicon

Motivated by applications to quantum computer architectures we study the change in the exchange interaction between neighbouring phosphorus donor electrons in silicon due to the application of voltage biases to surface control electrodes. These voltage biases create electro-static fields within the crystal substrate, perturbing the states of the donor electrons and thus altering the strength of the exchange interaction between them. We find that control gates of this kind can be used to either enhance, or reduce the strength of the interaction, by an amount that depends both on the magnitude and orientation of the donor separation.Comment: 5 Pages, 5 Figure

Optically induced spin to charge transduction in donor spin read-out

The proposed read-out configuration D+D- for the Kane Si:P architecture[Nature 393, 133 (1998)] depends on spin-dependent electron tunneling between donors, induced adiabatically by surface gates. However, previous work has shown that since the doubly occupied donor state is so shallow the dwell-time of the read-out state is less than the required time for measurement using a single electron transistor (SET). We propose and analyse single-spin read-out using optically induced spin to charge transduction, and show that the top gate biases, required for qubit selection, are significantly less than those demanded by the Kane scheme, thereby increasing the D+D- lifetime. Implications for singlet-triplet discrimination for electron spin qubits are also discussed.Comment: 8 pages, 10 figures; added reference, corrected typ

The entrepreneurial university and development of large-scale research infrastructure – exploring the emerging university function of collaboration and leadership

This paper aimed to explore the emerging university function of collaboration and leadership in developing large-scale research infrastructure (LRI). A qualitative approach, drawing from both primary and secondary data, was employed to delve deeper into the roles and aspects of the entrepreneurial university pertinent to LRI development. The study highlighted the need for the entrepreneurial university to establish a strategic direction for collaboration and leadership in LRIs. A conceptual model was crafted that delineated the central role of the entrepreneurial university, segmenting the findings into three research elements: (i) research and education (ii) collaboration, and (iii) utilization and impact. Actor perspectives from both academia and industry were included. The findings emphasized that entrepreneurial universities had to engage more robustly with external actors to foster practical research applications. Universities were found to require a more synergistic role. The model proposed that entrepreneurial universities should classify actors not only by their viewpoint but also by their potential role in LRI. Key actors were identified as belonging to LRI and multi-academic environments, with some being directly involved, while others were indirectly or peripherally engaged. Directly involved actors, including numerous academic and industrial users, had a clear understanding of LRI utility and engagement, whereas indirectly involved ones were curious yet unsure about LRI interaction

Developing a knowledge ecosystem for large-scale research infrastructure

Large-scale research infrastructures (RIs), such as MAX IV and European Spallation Source in Lund, Sweden, are considered critical for advancing science and addressing social challenges. These research facilities are central to research, innovation, and education; in playing a key role in developing and disseminating knowledge and technology. In this study, we develop a conceptual framework of a knowledge ecosystem for large-scale RIs. The study is explorative, with primary data from 13 interviews with key informants from different stakeholders in academia, industry, and policy. Secondary data were obtained from reports from national agencies that develop and operate research facilities and from industrial and regional governmental reports, internal reports, newsletters, and information from the facilities’ websites. We find that academia, industry, and policy, together with four themes, have an effect on the value proposition of these facilities, on geographical distances (nodes), catalysts, platforms, and hubs. Therefore, they will affect the structure and design of a knowledge ecosystem. Our framework explains knowledge ecosystem structure and design

Density-functional theory of polar insulators

We examine the density-functional theory of macroscopic insulators, obtained in the large-cluster limit or under periodic boundary conditions. For polar crystals, we find that the two procedures are not equivalent. In a large-cluster case, the exact exchange-correlation potential acquires a homogeneous ``electric field'' which is absent from the usual local approximations, and the Kohn-Sham electronic system becomes metallic. With periodic boundary conditions, such a field is forbidden, and the polarization deduced from Kohn-Sham wavefunctions is incorrect even if the exact functional is used