Coherent Interactions in Rare-Earth-Ion-Doped Crystals for Applications in Quantum Information Science

This thesis describes investigations of the use of cryogenically cooled rare-earth-ion-doped crystals for quantum information processing and quantum optics. Several aspects of the coherent interaction between light and rare-earth ions in solids are addressed. Quantum information science has given physicists new views of quantum mechanics. The transmission of quantum states has already found practical use and full scale quantum computers may one day perform computations and simulations that would be impossible on a conventional computer. The work presented in this thesis can be seen as a part of a broad effort to learn how to control and manipulate quantum mechanical systems, which will become necessary as science and technology continue to push ever deeper into the nanoscopic world. Coherent radiation, such as laser light, provides us with an ideal tool for these investigations and, along the way, we may also learn more about the quantum nature of light. Rare-earth ions in inorganic crystals have several unusual properties that are interesting for applications within quantum information science, including long coherence times and long-lived ground state sublevels that can be used for storage of quantum and classical information. As part of the work presented in this thesis, new materials have been investigated with respect to these properties, and ways to enhance the useful properties of the materials were explored. In one investigation, the lifetime of information stored in the ground state population distribution of Tm3 ions in YAG was shown to increase by several orders of magnitude with the application of a magnetic field. It is demonstrated how the optical inhomogeneous absorption profile can be prepared, so that the light only interacts with a selected group of ions, absorbing on a specific transition. Narrow absorbing structures, with widths approaching the optical homogeneous linewidth, have been prepared with no absorption in the surrounding spectral interval. This thesis addresses the use of such structures as hardware for quantum bits. Tailored pulses, capable of inducing controlled changes in the quantum states of the ions (qubits), even in the presence of unknown variations of coupling strengths and frequencies, have been realised experimentally and used for multiple transfer of ions between energy levels. Ion-ion interactions, which can be used for performing quantum logic operations, have been investigated in some detail. Techniques for selecting strongly interacting ions, by transferring weakly interacting ions to auxiliary states, have been demonstrated. A scheme for storing the quantum state of light in a solid, using photon-echo-like techniques, is proposed and analysed. In the proposed scheme, an optical wave packet is absorbed and subsequently re-emitted by an inhomogeneous absorption profile, which is tailored and externally controlled by the application of an electric field Additionally, an accumulated photon echo experiment has been performed using faint optical pulses. The experiment can be viewed as a demonstration of delayed self-interference of a single photon and as a demonstration of how a single photon can act as two of the fields in a photon echo process

Safe routes to school: leads to greater collaboration with public health and school officials

"Safe Routes to School is a collaborative effort involving multiple organizations, and has been integral in increasing partnerships between public health and school state-level officials as evidenced by the statewide case studies from California, Massachusetts, Mississippi and Oklahoma. The statewide case studies provided numerous examples of state level collaboration among officials that are resulting in important policy changes. Safe Routes to School has brought together Departments of Education and Public Health on Task Forces, Advisory Committees, Project Selection Committees and Project Development Committees. Working together on advancing SRTS on these committees has resulted in increased communications and understanding between the agencies, relationship building, opening communication channels and increased opportunities to spread a unified message about SRTS to make sure it is a successful program."Text document in PDF format.Cover title.Title from PDF title page (viewed on April 2, 2009)."Prepared by the Safe Routes to School National Partnership for the Centers for Disease Control and Prevention by Brooke Driesse.""December 2008."Mode of access: World Wide Web.Includes bibliographical references

Do Entrenched Manager Pay Their Workers More?

We present evidence on whether managerial entrenchment affects workers' pay, using a large panel dataset that matches public firms with detailed data on their subsidiaries and workers. We find that CEOs with a stronger grip on control pay their workers higher wages, but CEO ownership of cash flow rights mitigates such behavior. Unionized workers and executives are found to get a larger share of the higher pay. These findings do not seem to be driven by productivity differences or reverse causality, and are robust to a series of robustness checks. Our evidence is consistent with an agency model in which entrenched managers pay higher wages because they come with direct private benefits for the manager, such as lower-effort wage bargaining and better CEO-employee relations, and suggests more broadly an important link between the corporate governance of large public firms and labor market outcomes.Corporate governance; agency problems; private benefits; matched employer-employee data; wages

The Euro and Corporate Valuations

In this paper, we study the changes in corporate valuations induced by the adoption of the euro as the common currency in Europe. We use corporate-level data from seventeen European countries, of which eleven adopted the euro. We show that the introduction of the euro has increased Tobin\u27s Q-ratios by 17.1% in the {euro-area} countries that previously had weak currencies. Part of the increase in corporate valuations is explained by the decrease in interest rates and by the decrease in the cost of equity. The increases in Tobin\u27s Q are larger for firms that would be harmed by currency devaluations

The Euro and Corporate Financing Before the Crisis

We study the financing policies of European public corporations prior to the euro crisis. Using data from 11 euro countries and a control group of five other European countries over 1991–2006, we show that nonfinancial firms from euro countries with previously weak currencies considerably increased their debt financing after the introduction of the euro. The results are stronger for large firms, firms dependent on external financing, and for the latter part of the post-euro time period. Overall, the results support the hypothesis that the supply of capital increased following the introduction of the euro

Spatiotemporal Spike-Pattern Selectivity in Single Mixed-Signal Neurons with Balanced Synapses

Realizing the potential of mixed-signal neuromorphic processors for ultra-low-power inference and learning requires efficient use of their inhomogeneous analog circuitry as well as sparse, time-based information encoding and processing. Here, we investigate spike-timing-based spatiotemporal receptive fields of output-neurons in the Spatiotemporal Correlator (STC) network, for which we used excitatory-inhibitory balanced disynaptic inputs instead of dedicated axonal or neuronal delays. We present hardware-in-the-loop experiments with a mixed-signal DYNAP-SE neuromorphic processor, in which five-dimensional receptive fields of hardware neurons were mapped by randomly sampling input spike-patterns from a uniform distribution. We find that, when the balanced disynaptic elements are randomly programmed, some of the neurons display distinct receptive fields. Furthermore, we demonstrate how a neuron was tuned to detect a particular spatiotemporal feature, to which it initially was non-selective, by activating a different subset of the inhomogeneous analog synaptic circuits. The energy dissipation of the balanced synaptic elements is one order of magnitude lower per lateral connection (0.65 nJ vs 9.3 nJ per spike) than former delay-based neuromorphic hardware implementations. Thus, we show how the inhomogeneous synaptic circuits could be utilized for resource-efficient implementation of STC network layers, in a way that enables synapse-address reprogramming as a discrete mechanism for feature tuning.Comment: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

Distance of life

Moose is the most important big game animal in Sweden, with a great impact on its environment, yet little is known of their movements early in life and therefore we studied a moose population in northern Sweden – their dispersal from birth to death. We found that mean dispersal distance was 11,5 km ± 2 km (mean distance in kilometers ± 95% C.I.) and ranged between 120 meters and 76 km. Males dispersed further than females (p<0,0136), the mean distance for females (n=70) was 7,5 km ± 2,5 km and 14,5 ± 3,5 km for males (n=90). Moreover, dispersal significantly increased with age (p=0,0001). We also tested if sex interacted with age as an explaining variable for dispersal but no evidence was found (p=0,8637). To evaluate whether these patterns should be considered in the harvest and management of moose, we compared mean moose dispersal distance with the mean size (i.e. radius) of a VVO (hunting area). There was a clear significance that moose dispersed further than the radius of a mean-sized VVO. Our findings show that moose population in northern Sweden is highly dynamic in the sense of their spatial distribution and there’re also clear demographical divergences in their dispersal. This is important to both moose managers, who have serious ecological factors to govern and also to moose hunters, who will not shoot their “own” moose. Both factors show the importance of managing moose at the appropriate scale.Älg är det viktigaste jaktbara storviltet i Sverige med stor påverkan på sin omgivning. Trots det vet man inte så mycket om deras rörelsemönster och därför har vi studerat en älgpopulation i norra Sverige – en analys av deras spridning från födsel till död. Vi såg att medeldistansen var 11,5 km ± 2 km (medeldistans i kilometer ± 95% K.I.) med en spridning mellan 120 meter och 7,6 mil. Vi såg också att hanar spred sig längre än honor (p<0,0001) där medeldistansen för honor (n=70) var 7,5 km ± 2,5 km och 14,5 ± 3,5 km för hanar (n=90). Älgens spridning i relation till dess ålder var signifikant (p=0,0136) där distansen ökade med ökande ålder. Vi såg ingen signifikant skillnad då vi testade om kön var en förklarande variabel till åldersrelaterad spridning (p=0,8637). För att se om detta påverkar jakten och skötseln av älg jämförde vi viltvårdområdenas (VVO) medelstorlek (radie) med medeldistansen vid spridning för älg där vi såg att älg spred sig signifikant längre än medelradien av ett VVO. Våra resultat indikerar att älgstammarna i norra Sverige är mycket dynamiska med tanke på dess rumsliga fördelning där tydliga demografiska spridningsskillnader kan ses. Detta påverkar såväl älgförvaltare, med många komplexa ekologiska faktorer att ta hänsyn till såväl som jägare, vilka förmodligen inte kommer att skjuta deras ”egna” älgar under jakten

Gibraltar : den eviga konflikten?

This thesis is an argumentative analysis which utilizes the Toulmin model. The analysis is initially of a descriptive nature but progresses and transforms its intentions into a prescriptive and evidential form in a continuum. The materials which are processed are three opinion-forming articles published in august in English language newspapers. The analysis is performed by categorizing the elements of the argumentations and elevating their important aspects in order to make able the answering of the proposed questions which queries how the recent debate concerning Gibraltar is portrayed in the chosen newspapers and the relation this has with the status of Gibraltar as a British colony and whether this can affect a future change of said status. After separately analyzing the different components according to the theory of decolonization, the conclusion is reached which signifies the British debate concerning Gibraltar as a heterogeneous spectacle with the greatest difference lying in the recipient of the projected blame. The status of Gibraltar as a colony appears stern but its belonging to Britain appears less so. The possibility for co-sovereignty is a possibility. This however is unlikely to mean any noticeable change in the lives of Gibraltarian