Violation of a Leggett-Garg inequality with ideal non-invasive measurements

The quantum superposition principle states that an entity can exist in two different states simultaneously, counter to our 'classical' intuition. Is it possible to understand a given system's behaviour without such a concept? A test designed by Leggett and Garg can rule out this possibility. The test, originally intended for macroscopic objects, has been implemented in various systems. However to-date no experiment has employed the 'ideal negative result' measurements that are required for the most robust test. Here we introduce a general protocol for these special measurements using an ancillary system which acts as a local measuring device but which need not be perfectly prepared. We report an experimental realisation using spin-bearing phosphorus impurities in silicon. The results demonstrate the necessity of a non-classical picture for this class of microscopic system. Our procedure can be applied to systems of any size, whether individually controlled or in a spatial ensemble.Comment: 6+4 pages. Supplementary Methods section include

Improving Teaching and Learning in Introductory Physics

This thesis describes three studies designed to help students learn physics better and instructors teach physics more effectively in local circumstances. The first study investigated the effects of teaching approaches consisting of interactive engagement activities in two institutions. The teaching elements in the experimental classes were reading quizzes, interactive lecture demonstrations and student discussions. The control classes were taught in traditional style dominated by an instructor lecturing on concepts and problem solving examples. The cognitive improvement was measured by a standardized test and exam grades. The students in the experimental classes showed significant improvement in conceptual understanding and problem solving skills compared to the students in the control classes. While the experimental groups welcomed the modified instruction, they still held the view that the lecturer should play the dominant role of presenting the material. In the second study interviews with lecturers, teaching assistants and students revealed their perceptions of the utility of real-life materials in instruction. The students asserted that activities using real-life materials were interesting and useful. However, they still considered that elements of traditional instruction were very important in good teaching. The lack of knowledge of innovative teaching approaches may explain why the instructors were sceptical about the effectiveness of real-life materials in improving their students' understanding. To raise the instructors' awareness of issues in learning physics and to improve their knowledge of effective instruction, the third study discussed a department-based professional development course. The course incorporated interactive engagement activities and made connections to teaching and learning experiences. The course evaluation suggested that the participants became more open to new ideas and intended to implement what they had learned in the present and future academic career. The studies in this thesis have impacted on first year courses and raised the instructors' awareness of physics education issues. The emphasis of educational enterprises should be shifted from classroom changes to educating the instructors. Instead of simply modifying teaching practice, instructors should also undergo a transformation in beliefs and knowledge in pedagogy. It is only when all instructors are willing to undergo such a transformation that a significant achievement in teaching and learning will be realized

Non-invasive detection of animal nerve impulses with an atomic magnetometer operating near quantum limited sensitivity

Magnetic fields generated by human and animal organs, such as the heart, brain and nervous system carry information useful for biological and medical purposes. These magnetic fields are most commonly detected using cryogenically-cooled superconducting magnetometers. Here we present the frst detection of action potentials from an animal nerve using an optical atomic magnetometer. Using an optimal design we are able to achieve the sensitivity dominated by the quantum shot noise of light and quantum projection noise of atomic spins. Such sensitivity allows us to measure the nerve impulse with a miniature room-temperature sensor which is a critical advantage for biomedical applications. Positioning the sensor at a distance of a few millimeters from the nerve, corresponding to the distance between the skin and nerves in biological studies, we detect the magnetic field generated by an action potential of a frog sciatic nerve. From the magnetic field measurements we determine the activity of the nerve and the temporal shape of the nerve impulse. This work opens new ways towards implementing optical magnetometers as practical devices for medical diagnostics.Comment: Main text with figures, and methods and supplementary informatio

Crossing the Antarctica: Exploring the Effects of Appetite-Regulating Hormones and Indicators of Nutrition Status during a 93-Day Solo-Expedition

Future deep space astronauts must maintain adequate nutrition despite highly stressful, isolated, confined and dangerous environments. The present case-study investigated appetite regulating hormones, nutrition status, and physical and emotional stress in a space analog condition: an explorer conducting a 93-day unsupported solo crossing of Antarctica. Using the dried blood spot (DBS) method, the subject drew samples of his blood on a regular basis during the expedition. The DBSs were later analyzed for the appetite regulating hormones leptin and adiponectin. Energy intake and nutritional status were monitored by analysis of albumin and globulin (including their ratio). Interleukin-6 (IL-6) was also analyzed and used as an energy sensor. The results showed a marked reduction in levels of the appetite-reducing hormone, leptin, and the appetite stimulating hormone, adiponectin, during both extreme physical and psychological strain. Nutrition status showed a variation over the expedition, with below-normal levels during extreme psychological strain and levels abutting the lower bounds of the normal range during a phase dominated by extreme physical hardship. The IL-6 levels varied substantially, with levels above the normal range except during the recovery phase. It was concluded that a daily intake of 5058 to 5931 calories seemed to allow recovery of both appetite and nutritional status between extreme physical and psychological hardship during a long Arctic expedition. Furthermore, IL-6 may be a sensor in the muscle-liver, muscle-fat and muscle-brain crosstalk. These results may help guide nutrition planning for future astronaut crews, mountaineers and others involved in highly demanding missions.publishedVersio

Cancer Rehabilitation Indicators for Europe

Little is known of cancer rehabilitation needs in Europe. EUROCHIP-3 organised a group of experts to propose a list of population-based indicators used for describing cancer rehabilitation across Europe. The aim of this study is to present and discuss these indicators. A EUROCHIP-3 expert panel reached agreement on two types of indicators. (a) Cancer prevalence indicators. These were proposed as a means of characterising the burden of cancer rehabilitation needs by time from diagnosis and patient health status. These indicators can be estimated from cancer registry data or by collecting data on follow-up and treatments for samples of cases archived in cancer registries. (b) Indicators of rehabilitation success. These include: return to work, quality of life, and satisfaction of specific rehabilitation needs. Studies can be performed to estimate these indicators in individual countries, but to obtain comparable data across European countries it will be necessary to administer a questionnaire to randomly selected samples of patients from population-based cancer registry databases. However, three factors complicate questionnaire studies: patients may not be aware that they have cancer; incomplete participation in surveys could lead to bias; and national confidentiality laws in some cases prohibit cancer registries from approaching patients. Although these studies are expensive and difficult to perform, but as the number of cancer survivors increases, it is important to document their needs in order to provide information on cancer control