Quantum Entanglement and Communication Complexity

We consider a variation of the multi-party communication complexity scenario where the parties are supplied with an extra resource: particles in an entangled quantum state. We show that, although a prior quantum entanglement cannot be used to simulate a communication channel, it can reduce the communication complexity of functions in some cases. Specifically, we show that, for a particular function among three parties (each of which possesses part of the function's input), a prior quantum entanglement enables them to learn the value of the function with only three bits of communication occurring among the parties, whereas, without quantum entanglement, four bits of communication are necessary. We also show that, for a particular two-party probabilistic communication complexity problem, quantum entanglement results in less communication than is required with only classical random correlations (instead of quantum entanglement). These results are a noteworthy contrast to the well-known fact that quantum entanglement cannot be used to actually simulate communication among remote parties.Comment: 10 pages, latex, no figure

Gravitational Waves in Relativistic Theory of Gravitation

It is shown that, in the framework of Relativistic Theory of Gravitation with massive graviton, gravitational waves, due to the causality condition, do not bear negative energy flows.Comment: 4 page

Adiabatic Quantum Computation in Open Systems

We analyze the performance of adiabatic quantum computation (AQC) under the effect of decoherence. To this end, we introduce an inherently open-systems approach, based on a recent generalization of the adiabatic approximation. In contrast to closed systems, we show that a system may initially be in an adiabatic regime, but then undergo a transition to a regime where adiabaticity breaks down. As a consequence, the success of AQC depends sensitively on the competition between various pertinent rates, giving rise to optimality criteria.Comment: v2: 4 pages, 1 figure. Published versio

Probing spacetime foam with extragalactic sources

Due to quantum fluctuations, spacetime is probably ``foamy'' on very small scales. We propose to detect this texture of spacetime foam by looking for core-halo structures in the images of distant quasars. We find that the Very Large Telescope interferometer will be on the verge of being able to probe the fabric of spacetime when it reaches its design performance. Our method also allows us to use spacetime foam physics and physics of computation to infer the existence of dark energy/matter, independent of the evidence from recent cosmological observations.Comment: LaTeX, 11 pages, 1 figure; version submitted to PRL; several references added; very useful comments and suggestions by Eric Perlman incorporate

Feasibility of Buffalo Rearing on Pasture in Tropical Climate of Andaman and Nicobar Islands

The Andaman and Nicobar group of Islands form the Southern most tip of the Indian subcontinent, located (6-14° N latitude and 92-94°E longitude) in the South Eastern part of the Bay of Bengal .There are 572 Islands of which only 37 are currently inhabited. The Islands are beautiful and unique. The indigenous plants, animals, livestock, and marine life contribute to uniqueness of these Islands. The total livestock population has increased to many fold from meager 38.6 thousand in 1961 to 154.75 thousand in 2012. The buffalo constitute 5.08 per cent of the livestock of Andaman and Nicobar Islands. The buffaloes are of mongrel populations which are inheritance from Murrah, Nagpuri, Bhadawari, Marathwada and nondescript population. They are water buffalo and have very low milk yield. The herd size varies from 4 to 21. The buffalo populations in these groups of islands are recorded to be 7863 as per 2012 livestock census. The milk production from the buffalo is 1.843 thousand tons for the year 2013-14. Standard feeding systems indicate that the feed and fodder available are not sufficient to meet the requirement of the livestock. Severe shortages of both dry and green fodder remain the major concern for production of milk from the present livestock population. It is estimated a shortages of dry and green fodder are 51.80 percent and 99.56 per cent respectively (Kundu et al., 2010). However these Island livestock has adapted themselves to the subsistence type of feeding management for production purposes. Due to non availability of regular and ample fodder for the stall feeding of the livestock, owners resort to letting their animals stray for grazing. The grassland or fallow lands available in the area are being used for grazing for the buffalo. The grass land of Andaman has been developed due to the deforestation of virgin forest and consists of under shurbs, shrubs and trees besides the grasses and forbs, either in the isolation and scattered of in large and small patches with variable density. Climate of these islands have a tropical, maritime climate. The temperature varies from 21.6°C to 32.5° C, the average annual rainfall is about 3100 mm distributed over 8-9 months with range of relative humidity from 74 to 90 per cent throughout the year. Intense solar radiation is observed between February to April. Out of 37 inhabitant islands, 12 islands have no livestock whatsoever and another 4 islands have populations of less than 200. The cattle, buffalo and goat are the predominant livestock species in Andaman group of Islands where as pig and goat are the predominant species for Nicobar group of Islands. The growth rate of selected categories of livestock as per the quinquenial census of both 1997 and 2003 showed a positive growth. The milk production was also increased from 23.18 thousand tons in 2000-01 to 26.42 thousand tons in 2003-04 registering a growth rate of 13.97 per cent during the period of four years. However the growth rate of cattle, buffalo, goat and pig has decreased due to loss of livestock during tsunami which struck these islands on 26th December 2004. It also caused extensive damage to the agricultural land specially the flat land suitable to paddy cultivation. Around 8068.71 hectare paddy land was assessed to be damaged by tsunami/earth quake out of 12000 ha flat land suitable for paddy cultivation. This caused severe shortages of paddy straw for feeding the livestock. Both decrease in livestock population and the non availability of straw resulted in reduction of total milk to 23.890 thousand tons in 2007-2008 registering decline of 9.57 per cent over the 2003-04. The populations of livestock remain in decreasing trend (19th livestock census report). However the milk production recorded as increasing trend with 25.759 thousand tons in the year 2011-12 over 2007-2008

Self-reported domain-specific and accelerometer-based physical activity and sedentary behaviour in relation to psychological distress among an urban Asian population

Background: The interpretation of previous studies on the association of physical activity and sedentary behaviour with psychological health is limited by the use of mostly self-reported physical activity and sedentary behaviour, and a focus on Western populations. We aimed to explore the association of self-reported and devise-based measures of physical activity and sedentary behaviour domains on psychological distress in an urban multi-ethnic Asian population. Methods: From a population-based cross-sectional study of adults aged 18-79 years, data were used from an overall sample (n = 2653) with complete self-reported total physical activity/sedentary behaviour and domain-specific physical activity data, and a subsample (n = 703) with self-reported domain-specific sedentary behaviour and accelerometry data. Physical activity and sedentary behaviour data were collected using the Global Physical Activity Questionnaire (GPAQ), a domain-specific sedentary behaviour questionnaire and accelerometers. The Kessler Screening Scale (K6) and General Health Questionnaire (GHQ-12) were used to assess psychological distress. Logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals, adjusted for socio-demographic and lifestyle characteristics. Results: The sample comprised 45.0% men (median age = 45.0 years). The prevalence of psychological distress based on the K6 and GHQ-12 was 8.4% and 21.7%, respectively. In the adjusted model, higher levels of self-reported moderate-to-vigorous physical activity (MVPA) were associated with significantly higher odds for K6 (OR = 1.47 [1.03-2.10]; p-trend = 0.03) but not GHQ-12 (OR = 0.97 [0.77-1.23]; p-trend = 0.79), when comparing the highest with the lowest tertile. Accelerometry-assessed MVPA was not significantly associated with K6 (p-trend = 0.50) nor GHQ-12 (p-trend = 0.74). The highest tertile of leisure-time physical activity, but not work- or transport-domain activity, was associated with less psychological distress using K6 (OR = 0.65 [0.43-0.97]; p-trend = 0.02) and GHQ-12 (OR = 0.72 [0.55-0.93]; p-trend = 0.01). Self-reported sedentary behaviour was not associated with K6 (p-trend = 0.90) and GHQ-12 (p-trend = 0.33). The highest tertile of accelerometry-assessed sedentary behaviour was associated with significantly higher odds for K6 (OR = 1.93 [1.00-3.75]; p-trend = 0.04), but not GHQ-12 (OR = 1.34 [0.86-2.08]; p-trend = 0.18). Conclusions: Higher levels of leisure-time physical activity and lower levels of accelerometer-based sedentary behaviour were associated with lower psychological distress. This study underscores the importance of assessing accelerometer-based and domain-specific activity in relation to mental health, instead of solely focusing on total volume of activity

Universality of Entanglement and Quantum Computation Complexity

We study the universality of scaling of entanglement in Shor's factoring algorithm and in adiabatic quantum algorithms across a quantum phase transition for both the NP-complete Exact Cover problem as well as the Grover's problem. The analytic result for Shor's algorithm shows a linear scaling of the entropy in terms of the number of qubits, therefore difficulting the possibility of an efficient classical simulation protocol. A similar result is obtained numerically for the quantum adiabatic evolution Exact Cover algorithm, which also shows universality of the quantum phase transition the system evolves nearby. On the other hand, entanglement in Grover's adiabatic algorithm remains a bounded quantity even at the critical point. A classification of scaling of entanglement appears as a natural grading of the computational complexity of simulating quantum phase transitions.Comment: 30 pages, 17 figures, accepted for publication in PR

Classical and Quantum Annealing in the Median of Three Satisfiability

We determine the classical and quantum complexities of a specific ensemble of three-satisfiability problems with a unique satisfying assignment for up to N=100 and N=80 variables, respectively. In the classical limit we employ generalized ensemble techniques and measure the time that a Markovian Monte Carlo process spends in searching classical ground states. In the quantum limit we determine the maximum finite correlation length along a quantum adiabatic trajectory determined by the linear sweep of the adiabatic control parameter in the Hamiltonian composed of the problem Hamiltonian and the constant transverse field Hamiltonian. In the median of our ensemble both complexities diverge exponentially with the number of variables. Hence, standard, conventional adiabatic quantum computation fails to reduce the computational complexity to polynomial. Moreover, the growth-rate constant in the quantum limit is 3.8 times as large as the one in the classical limit, making classical fluctuations more beneficial than quantum fluctuations in ground-state searches

Single-electron tunneling in InP nanowires

We report on the fabrication and electrical characterization of field-effect devices based on wire-shaped InP crystals grown from Au catalyst particles by a vapor-liquid-solid process. Our InP wires are n-type doped with diameters in the 40-55 nm range and lengths of several microns. After being deposited on an oxidized Si substrate, wires are contacted individually via e-beam fabricated Ti/Al electrodes. We obtain contact resistances as low as ~10 kOhm, with minor temperature dependence. The distance between the electrodes varies between 0.2 and 2 micron. The electron density in the wires is changed with a back gate. Low-temperature transport measurements show Coulomb-blockade behavior with single-electron charging energies of ~1 meV. We also demonstrate energy quantization resulting from the confinement in the wire.Comment: 4 pages, 3 figure