A quantum interface between light and nuclear spins in quantum dots

The coherent coupling of flying photonic qubits to stationary matter-based qubits is an essential building block for quantum communication networks. We show how such a quantum interface can be realized between a traveling-wave optical field and the polarized nuclear spins in a singly charged quantum dot strongly coupled to a high-finesse optical cavity. By adiabatically eliminating the electron a direct effective coupling is achieved. Depending on the laser field applied, interactions that enable either write-in or read-out are obtained.Comment: 10 pages, 5 figures, final versio

Unexpected systematic degeneracy in a system of two coupled Gaudin models with homogeneous couplings

We report an unexpected systematic degeneracy between different multiplets in an inversion symmetric system of two coupled Gaudin models with homogeneous couplings, as occurring for example in the context of solid state quantum information processing. We construct the full degenerate subspace (being of macroscopic dimension), which turns out to lie in the kernel of the commutator between the two Gaudin models and the coupling term. Finally we investigate to what extend the degeneracy is related to the inversion symmetry of the system and find that indeed there is a large class of systems showing the same type of degeneracy.Comment: 13 pages, 4 figure

Writing IS Teaching Cases: Guidelines for JISE Submission

Over the past year, JISE began accepting Teaching Cases for publication. Many information systems (IS) academicians and professionals have valuable experiences that are ripe for translating into cases. Students and instructors would benefit from the communication of these experiences into realistic, well-written cases to promote active learning. To encourage case submissions, the purpose of this article is twofold: (1) to provide potential authors with helpful advice and suggestions for writing case manuscripts; and (2) to communicate JISE guidelines for Teaching Case submissions. This paper is designed to serve as a resource for writers who are interested in developing Teaching Cases for publication

A Scalable Information Theoretic Approach to Distributed Robot Coordination

This paper presents a scalable information theoretic approach to infer the state of an environment by distributively controlling robots equipped with sensors. The robots iteratively estimate the environment state using a recursive Bayesian filter, while continuously moving to improve the quality of the estimate by following the gradient of mutual information. Both the filter and the controller use a novel algorithm for approximating the robots' joint measurement probabilities, which combines consensus (for decentralization) and sampling (for scalability). The approximations are shown to approach the true joint measurement probabilities as the size of the consensus rounds grows or as the network becomes complete. The resulting gradient controller runs in constant time with respect to the number of robots, and linear time with respect to the number of sensor measurements and environment discretization cells, while traditional mutual information methods are exponential in all of these quantities. Furthermore, the controller is proven to be convergent between consensus rounds and, under certain conditions, is locally optimal. The complete distributed inference and coordination algorithm is demonstrated in experiments with five quad-rotor flying robots and simulations with 100 robots.This work is sponsored by the Department of the Air Force under Air Force contract number FA8721-05-C-0002. The opinions, interpretations, recommendations, and conclusions are those of the authors and are not necessarily endorsed by the United States Government. This work is also supported in part by ARO grant number W911NF-05-1-0219, ONR grant number N00014-09-1-1051, NSF grant number EFRI-0735953, ARL grant number W911NF-08-2-0004, MIT Lincoln Laboratory, the European Commission, and the Boeing Company

Interfacing nuclear spins in quantum dots to cavity or traveling-wave fields

We show how to realize a quantum interface between optical fields and the polarized nuclear spins in a singly charged quantum dot, which is strongly coupled to a high-finesse optical cavity. An effective direct coupling between cavity and nuclear spins is obtained by adiabatically eliminating the (far detuned) excitonic and electronic states. The requirements needed to map qubit and continuous variable states of cavity or traveling-wave fields to the collective nuclear spin are investigated: For cavity fields, we consider adiabatic passage processes to transfer the states. It is seen that a significant improvement in cavity lifetimes beyond present-day technology would be required for a quantum interface. We then turn to a scheme which couples the nuclei to the output field of the cavity and can tolerate significantly shorter cavity lifetimes. We show that the lifetimes reported in the literature and the recently achieved nuclear polarization of ~90% allow both high-fidelity read-out and write-in of quantum information between the nuclear spins and the output field. We discuss the performance of the scheme and provide a convenient description of the dipolar dynamics of the nuclei for highly polarized spins, demonstrating that this process does not affect the performance of our protocol.Comment: 37 pages, 14 figure

The Health Outcomes and Health Service Needs of the Martu and Nyiyaparli People of Northwest Western Australia: A Grey Literature Review

Introduction: Health outcomes for Australian Aboriginal and Torres Strait peoples are very poor. This is considerably worse in remote regions. The East Pilbara, where the Aboriginal and Torres Strait Islander communities of the Martu and Nyiyaparli people reside, is one such remote region. Methods: This review explored the grey literature relating to the health services and health outcomes of the Martu and Nyiyaparli people. Search strategies included specific search terms as well as the systematic search of specific websites likely to inform this review. To ensure relevance of the data, the review incorporated documents published in the last five years and obtained statistical data at two different population levels (SA3 and Indigenous Area). Both SA3s and IAREs are geographical areas utilised by the Australian Bureau of Statistics for the attainment of statistical data; however, IAREs were created for more specific data related to Aboriginal and Torres Strait Islander people. Results: The main findings from this review were that health outcomes for the Aboriginal and Torres Strait Islander peoples of the East Pilbara were poor, with health indicator trends that were worse than nationwide averages. Additionally, the review found that the healthcare workforce shortages common to very remote areas across Australia were particularly problematic in the East Pilbara. Conclusion: In addition to seeking improved health outcomes, this project responds to calls from this community to move from the ‘repair shop’ model of healthcare to an upstream preventative model by providing a context of the current health issues in this East Pilbara region

Asymmetric optical nuclear spin pumping in a single uncharged quantum dot

A highly asymmetric dynamic nuclear spin pumping is observed in a single self assembled InGaAs quantum dot subject to resonant optical pumping of the neutral exciton transition leading to a large maximum polarization of 54%. This dynamic nuclear polarization is found to be much stronger following pumping of the higher energy Zeeman state. Time-resolved measurements allow us to directly monitor the buildup of the nuclear spin polarization in real time and to quantitatively study the dynamics of the process. A strong dependence of the observed dynamic nuclear polarization on the applied magnetic field is found, with resonances in the pumping efficiency being observed for particular magnetic fields. We develop a model that fully accounts for the observed behaviour, where the pumping of the nuclear spin system is due to hyperfine-mediated spin flip transitions between the states of the neutral exciton manifold.Comment: published version; 4+ pages, 3 figures (eps

Mathematical Philology: Entropy Information in Refining Classical Texts' Reconstruction, and Early Philologists' Anticipation of Information Theory

Philologists reconstructing ancient texts from variously miscopied manuscripts anticipated information theorists by centuries in conceptualizing information in terms of probability. An example is the editorial principle difficilior lectio potior (DLP): in choosing between otherwise acceptable alternative wordings in different manuscripts, “the more difficult reading [is] preferable.” As philologists at least as early as Erasmus observed (and as information theory's version of the second law of thermodynamics would predict), scribal errors tend to replace less frequent and hence entropically more information-rich wordings with more frequent ones. Without measurements, it has been unclear how effectively DLP has been used in the reconstruction of texts, and how effectively it could be used. We analyze a case history of acknowledged editorial excellence that mimics an experiment: the reconstruction of Lucretius's De Rerum Natura, beginning with Lachmann's landmark 1850 edition based on the two oldest manuscripts then known. Treating words as characters in a code, and taking the occurrence frequencies of words from a current, more broadly based edition, we calculate the difference in entropy information between Lachmann's 756 pairs of grammatically acceptable alternatives. His choices average 0.26±0.20 bits higher in entropy information (95% confidence interval, P = 0.005), as against the single bit that determines the outcome of a coin toss, and the average 2.16±0.10 bits (95%) of (predominantly meaningless) entropy information if the rarer word had always been chosen. As a channel width, 0.26±0.20 bits/word corresponds to a 0.790.79+0.09−0.15 likelihood of the rarer word being the one accepted in the reference edition, which is consistent with the observed 547/756 = 0.72±0.03 (95%). Statistically informed application of DLP can recover substantial amounts of semantically meaningful entropy information from noise; hence the extension copiosior informatione lectio potior, “the reading richer in information [is] preferable.” New applications of information theory promise continued refinement in the reconstruction of culturally fundamental texts