Practical Relativistic Bit Commitment.

Bit commitment is a fundamental cryptographic primitive in which Alice wishes to commit a secret bit to Bob. Perfectly secure bit commitment between two mistrustful parties is impossible through an asynchronous exchange of quantum information. Perfect security is, however, possible when Alice and Bob each split into several agents exchanging classical information at times and locations suitably chosen to satisfy specific relativistic constraints. In this Letter we first revisit a previously proposed scheme [C. Crépeau et al., Lect. Notes Comput. Sci. 7073, 407 (2011)] that realizes bit commitment using only classical communication. We prove that the protocol is secure against quantum adversaries for a duration limited by the light-speed communication time between the locations of the agents. We then propose a novel multiround scheme based on finite-field arithmetic that extends the commitment time beyond this limit, and we prove its security against classical attacks. Finally, we present an implementation of these protocols using dedicated hardware and we demonstrate a 2 ms-long bit commitment over a distance of 131 km. By positioning the agents on antipodal points on the surface of Earth, the commitment time could possibly be extended to 212 ms.

Experimental bit commitment based on quantum communication and special relativity.

Bit commitment is a fundamental cryptographic primitive in which Bob wishes to commit a secret bit to Alice. Perfectly secure bit commitment between two mistrustful parties is impossible through asynchronous exchange of quantum information. Perfect security is however possible when Alice and Bob split into several agents exchanging classical and quantum information at times and locations suitably chosen to satisfy specific relativistic constraints. Here we report on an implementation of a bit commitment protocol using quantum communication and special relativity. Our protocol is based on [A. Kent, Phys. Rev. Lett. 109, 130501 (2012)] and has the advantage that it is practically feasible with arbitrary large separations between the agents in order to maximize the commitment time. By positioning agents in Geneva and Singapore, we obtain a commitment time of 15 ms. A security analysis considering experimental imperfections and finite statistics is presented.

Continuous variable quantum key distribution: finite-key analysis of composable security against coherent attacks.

We provide a security analysis for continuous variable quantum key distribution protocols based on the transmission of two-mode squeezed vacuum states measured via homodyne detection. We employ a version of the entropic uncertainty relation for smooth entropies to give a lower bound on the number of secret bits which can be extracted from a finite number of runs of the protocol. This bound is valid under general coherent attacks, and gives rise to keys which are composably secure. For comparison, we also give a lower bound valid under the assumption of collective attacks. For both scenarios, we find positive key rates using experimental parameters reachable today.

A universal test for gravitational decoherence.

Quantum mechanics and the theory of gravity are presently not compatible. A particular question is whether gravity causes decoherence. Several models for gravitational decoherence have been proposed, not all of which can be described quantum mechanically. Since quantum mechanics may need to be modified, one may question the use of quantum mechanics as a calculational tool to draw conclusions from the data of experiments concerning gravity. Here we propose a general method to estimate gravitational decoherence in an experiment that allows us to draw conclusions in any physical theory where the no-signalling principle holds, even if quantum mechanics needs to be modified. As an example, we propose a concrete experiment using optomechanics. Our work raises the interesting question whether other properties of nature could similarly be established from experimental observations alone-that is, without already having a rather well-formed theory of nature to make sense of experimental data.

Psychoactive drug use among medical doctors is higher than in the general population.

We surveyed a representative sample of practising physicians and a representative sample of subjects from the Swiss general population (SOMIPOPS Survey) concerning their annual use of sleeping pills and tranquillizers. 77% of the physicians (n = 466) and 72% of the general population (n = 4255) responded. After adjustment for age and sex 37.1% of the doctors (general population 21.1% P less than 0.001) claimed to have taken these drugs for therapeutic purposes. The proportion of psychiatrists who reported taking sleeping pills and tranquillizers daily (10.6%) were significantly greater than for the population of doctors as a whole and for the general population (P less than 0.05). Regular users (i.e. subjects taking one mood altering drug at least once a week) accounted for 11.1% of the medical population compared with 6.8% of the general population (P less than 0.01). This over-consumption was wholly due to the greater number of regular users of psychoactive drugs amongst doctors less than 50 years of age relative to the general population or to subjects in higher management (from P less than 0.05 to P less than 0.001). Without this specific over-use, members of the medical profession would not have been found to use more psychoactive drugs than the general population and the executives. This result suggests that it would be worth investigating the mechanisms of response and adjustment (coping) to the specific stress that appears to be inherent in the exercise of medical practice.

[Anxiety and stress in the nursing staff. A comparative study between intensive care and general wards]. / Ansia e stress del personale infermieristico. Analisi comparata tra Terapia Intensiva e reparti di base.

We studied a population of 463 nurses working in intensive care units--ICUs--(distributed in 51 italian hospitals), and 216 nurses working in general medicine units (distributed in 17 italian hospitals). They we asked to fill in a form including: 1) general data and his/her work environment, and 2) some standardized scales (HAD A and D, STAI Y-1 and Y-2, MBI) for estimation of anxiety, depression and "burnout" syndrome. We used also the "P questions", evaluating the different situations of work environment causing anxiety. The aims of the study were to evaluate the effectiveness of different scales and the influence of general medicine and intensive care environment on psychological features. Among different scales estimating anxiety, the STAI Y-2, valuing a chronic anxiety status, results to be efficient, beside the already tested HAD A. The intensive care environment did not seem to be more stressful for nurses staff rather than general medicine units. Furthermore, nurses operating in general medicine units have a major tendency to depression; their work environment seems to favour the development of anxiety. Finally, it results that general medicine units cause a more severe "burnout" syndrome in their nurses staff rather than ICUs.

Proposing phase I studies: patients', relatives', nurses' and specialists' perceptions.

PURPOSE: As of now the primary objective of studies on informed consent in phase I trials has been to assess patients' expectations and reasons for participation. We have previously shown that the quantity of information provided through a procedure of subsequent oral interviews with patients was adequate while the attention paid by the physician to the emotional needs and concerns of patients was not. We wanted therefore to assess and compare the perceptions of the information provided about the investigational study of patients, relatives, the research nurse and the investigator responsible for the phase I trial and the impact this information had on the patients' level of anxiety and depression. PATIENTS AND METHODS: The participation to a phase I study was proposed to patients through two subsequent interviews, the latter attended also by patients' relatives, the research nurse and the investigator coordinating the phase I trial. After the second interview, attendees were requested to complete a questionnaire assessing the principal reason for participating in the study and the informative, emotional and interactive dimension of the information. Patients were also requested to complete the Hospital Anxiety and Depression (HAD) scale before and after the second interview. RESULTS: The completed questionnaires of 31 of 42 patients were retrieved and analysed. The possibility to benefit from the study was indicated as the main reason for participating by 59% of the patients while it was judged to be the case in 78% and 86% of the patients by the nurse and the investigator, respectively. The information was judged to be clear and sufficient in almost all cases by all attendees, while the investigator judged that a lower percentage of patients felt at ease and could express their main worries during the interview, had been helped and were less worried after it than it was judged by the nurse and the relatives. Patients' state of anxiety and depression was not adversely affected by the information provided. CONCLUSIONS: Informing patients on the option of receiving an investigational treatment within a phase I study is feasible and can be done in a way felt appropriate by patients and relatives, nursing and medical professionals. Providing information in an appropriate manner does not increase patients' anxiety and depression. Divergence between the aims and interests of the investigators and patients might explain the difference in the evaluation of physician, a problem which could perhaps be partially overcome by the application of innovative phase I designs.

Informed consent for phase I studies: evaluation of quantity and quality of information provided to patients.

BACKGROUND: The process by which patients are informed and their consent is obtained in phase I trials has thus far been only marginally studied. Since 1986 we have followed an oral procedure, consisting of three consecutive conversations in which the investigator responsible for phase I studies, the research nurse and the patients' relatives and/or friends also participate, followed by the patients signing of a written consent form. It is required that six items of information considered essential by our staff be conveyed to patients by the responsible investigator. Meerwein's model, which defines three main dimensions of the informing process (the information itself, the emotional and interactive aspects), has been studied to ascertain whether it can be applied to evaluate the quality of the information proffered. METHODS: Thirty-two conversations were taped, transcribed and evaluated by one psychiatrist and one psychologist. A quantitative analysis of information was performed by calculating the number of patients to whom the essential items of information had been conveyed. The qualitative analysis was performed by rating on a five-point scoring system, from 1 (very bad) to 5 (excellent), the three dimensions of the informing process for each patient and by calculating for each dimension the mean score of the constituent items. RESULTS: Complete information about the characteristics of the phase I drug and the modalities of the treatment and follow up was given to almost 80% of the patients. All but one of the items of the information dimension scored 3.5 or higher, with the one related to the assessment by the doctor of the patient's understanding at the end of the consultation scoring less than 3 in 53% of the patients. All items of the emotional dimension scored higher than 3.5. Greater difficulty was encountered by the physician with the interactive dimension, the lowest mean scores being reported on the items related to the doctor's awareness of the indirectly expressed anxieties of the patients. In 71% of the consultations the three dimensions of information scored more than 3 and balanced one another, indicating a successful consultation by the Meerwein model. CONCLUSIONS: The informed consent procedure applied was satisfactory from a quantitative point of view, and the main items of information were acceptable to the patients. Meerweins's model proved to be applicable and useful for identifying pitfalls in communication. Greater attention should be paid to the indirect messages and implied criticisms of the patients to improve their participation in decision making. Physicians should become more skillful in providing adequate information and improve their methods of communication.

The Perceived Adjustment to Chronic Illness Scale (PACIS): a global indicator of coping for operable breast cancer patients in clinical trials. Swiss Group for Clinical Cancer Research (SAKK) and the International Breast Cancer Study Group (IBCSG).

Subjective well-being is a major aspect of quality of life and is therefore increasingly used as an endpoint in clinical trials. It is influenced to a great extent by the complex process of coping with the disease and its treatment. Assessment of coping is methodologically demanding, especially in large clinical trials. We therefore developed a single-item measure, the Perceived Adjustment to Chronic Illness Scale (PACIS), as an indicator of coping, complementary to other scales related to quality of life. We sought to validate this instrument in a subgroup of 121 Swiss patients participating in the International Breast Cancer Study Group (IBCSG) adjuvant trials. At months 3 and 6 of adjuvant treatment PACIS showed a distinct pattern of highly significant rank correlations with several disease- and treatment-related problem areas from the Herschbach coping inventory (FBBK); 42% of the variance of PACIS at month 3 was explained by the FBBK (P = .0001). The portion of explained variance was considerably higher for the Italian- (70%) than for the German-speaking (30%) subgroups. Patients who rated more effort to cope with their disease on PACIS indicated more frequent use of 3 of 15 coping strategies in relation to psychological distress. These were "crying and becoming desperate", "taking tranquillizers and alcohol" and "other people are far worse off". These three coping strategies may define a high-risk group for poor psychosocial outcome. Patients whose PACIS scores showed that it required less effort to cope tended to use the strategy "seeing a positive side of the problem". We conclude that PACIS can be used as a global indicator of the coping process in large multicultural clinical trials of adjuvant therapy for breast cancer.