Entanglement in a Valence-Bond-Solid State

We study entanglement in Valence-Bond-Solid state. It describes the ground state of Affleck, Kennedy, Lieb and Tasaki quantum spin chain. The AKLT model has a gap and open boundary conditions. We calculate an entropy of a subsystem (continuous block of spins). It quantifies the entanglement of this block with the rest of the ground state. We prove that the entanglement approaches a constant value exponentially fast as the size of the subsystem increases. Actually we proved that the density matrix of the continuous block of spins depends only on the length of the block, but not on the total size of the chain [distance to the ends also not essential]. We also study reduced density matrices of two spins both in the bulk and on the boundary. We evaluated concurrencies.Comment: 4pages, no figure

Scheme for direct measurement of a general two-qubit Hamiltonian

The construction of two-qubit gates appropriate for universal quantum computation is of enormous importance to quantum information processing. Building such gates is dependent on accurate knowledge of the interaction dynamics between two qubit systems. This letter will present a systematic method for reconstructing the full two-qubit interaction Hamiltonian through experimental measures of concurrence. This not only gives a convenient method for constructing two qubit quantum gates, but can also be used to experimentally determine various Hamiltonian parameters in physical systems. We show explicitly how this method can be employed to determine the first and second order spin-orbit corrections to the exchange coupling in quantum dots.Comment: 4 Pages, 1 Figur

An Entailment Relation for Reasoning on the Web

Reasoning on the Web is receiving an increasing attention because of emerging fields such as Web adaption and Semantic Web. Indeed, the advanced functionalities striven for in these fields call for reasoning capabilities. Reasoning on the Web, however, is usually done using existing techniques rarely fitting the Web. As a consequence, additional data processing like data conversion from Web formats (e.g. XML or HTML) into some other formats (e.g. classical logic terms and formulas) is often needed and aspects of the Web (e.g. its inherent inconsistency) are neglected. This article first gives requirements for an entailment tuned to reasoning on the Web. Then, it describes how classical logic’s entailment can be modified so as to enforce these requirements. Finally, it discusses how the proposed entailment can be used in applying logic programming to reasoning on the Web

Automated precision alignment of optical components for hydroxide catalysis bonding

We describe an interferometric system that can measure the alignment and separation of a polished face of a optical component and an adjacent polished surface. Accuracies achieved are ∼ 1μrad for the relative angles in two orthogonal directions and ∼ 30μm in separation. We describe the use of this readout system to automate the process of hydroxide catalysis bonding of a fused-silica component to a fused-silica baseplate. The complete alignment and bonding sequence was typically achieved in a timescale of a few minutes, followed by an initial cure of 10 minutes. A series of bonds were performed using two fluids - a simple sodium hydroxide solution and a sodium hydroxide solution with some sodium silicate solution added. In each case we achieved final bonded component angular alignment within 10 μrad and position in the critical direction within 4 μm of the planned targets. The small movements of the component during the initial bonding and curing phases were monitored. The bonds made using the sodium silicate mixture achieved their final bonded alignment over a period of ∼ 15 hours. Bonds using the simple sodium hydroxide solution achieved their final alignment in a much shorter time of a few minutes. The automated system promises to speed the manufacture of precision-aligned assemblies using hydroxide catalysis bonding by more than an order of magnitude over the more manual approach used to build the optical interferometer at the heart of the recent ESA LISA Pathfinder technology demonstrator mission. This novel approach will be key to the time-efficient and low-risk manufacture of the complex optical systems needed for the forthcoming ESA spaceborne gravitational waves observatory mission, provisionally named LISA

Validity, reliability, acceptability, and utility of the Social Inclusion Questionnaire User Experience (SInQUE): a clinical tool to facilitate social inclusion amongst people with severe mental health problems.

BACKGROUND: Individuals with severe mental health problems are at risk of social exclusion, which may complicate their recovery. Mental health and social care staff have, until now, had no valid or reliable way of assessing their clients' social inclusion. The Social Inclusion Questionnaire User Experience (SInQUE) was developed to address this. It assesses five domains: social integration; productivity; consumption; access to services; and political engagement, in the year prior to first psychiatric admission (T1) and the year prior to interview (T2) from which a total score at each time point can be calculated. AIMS: To establish the validity, reliability, and acceptability of the SInQUE in individuals with a broad range of psychiatric diagnoses receiving care from community mental health services and its utility for mental health staff. METHOD: Participants were 192 mental health service users with psychosis, personality disorder, or common mental disorder (e.g., depression, anxiety) who completed the SInQUE alongside other validated outcome measures. Test-retest reliability was assessed in a sub-sample of 30 participants and inter-rater reliability was assessed in 11 participants. SInQUE ratings of 28 participants were compared with those of a sibling with no experience of mental illness to account for shared socio-cultural factors. Acceptability and utility of the tool were assessed using completion rates and focus groups with staff. RESULTS: The SInQUE demonstrated acceptable convergent validity. The total score and the Social Integration domain score were strongly correlated with quality of life, both in the full sample and in the three diagnostic groups. Discriminant validity and test-retest reliability were established across all domains, although the test-retest reliability on scores for the Service Access and Political Engagement domains prior to first admission to hospital (T1) was lower than other domains. Inter-rater reliability was excellent for all domains at T1 and T2. CONCLUSIONS: The component of the SInQUE that assesses current social inclusion has good psychometric properties and can be recommended for use by mental health staff

Puerto Rico - Tax Haven or Tax Trap

This article does not encompass the entire subject of foreign taxation but is limited to two specific questions involved therein: 1. Where does a sale take place for purposes of Federal Taxation? 2. If it is determined that the sale takes place partly within and partly without the U. S., how much of the income from such sales is taxable to the U. S.

Construction of rugged, ultrastable optical assemblies with optical component alignment at the few microradian level

A method for constructing quasimonolithic, precision-aligned optical assemblies is presented. Hydroxide-catalysis bonding is used, adapted to allow optimization of component fine alignment prior to the bond setting. We demonstrate the technique by bonding a fused silica mirror substrate to a fused silica baseplate. In-plane component placement at the submicrometer level is achieved, resulting in angular control of a reflected laser beam at the sub-10-μrad level. Within the context of the LISA Pathfinder mission, the technique has been demonstrated as suitable for use in space-flight applications. It is expected that there will also be applications in a wide range of areas where accuracy, stability, and strength of optical assemblies are important

Potential for Acid Snowmelt in the Wasatch Mountains

Snowmelt collected from snow cores taken from the 1982 spring snowpack in the Wasatch Mountains of northern Utah lacked mineral acidity and retained enough buffering capacity in the form of calcium and magnesium bicarbonates to titrate additional inputs of strong acid equivalent to the amount apparently already neutralized. While acid anion concentrations were higher than those found in pristine areas, they were much lower than those reported for winter precipitation in other western areas experiencing acidification of precipitation. Snowmelt pH ranged from 5.62 to 6.88 (mean = 6.17), and sulfate was relatively more important than nitrate, showing an average equivalent ratio of 3.1:1. Patterns of pH indicated decreasing pH with distance from sources of soil-derived buffering capacity in the semiarid valleys to the east. Although acid anion concentration patterns failed to point to pollution sources along the Wasatch Front, chloride concentration patterns indicated that the Salt Lake Valley airshed influenced snow chemistry in the mountains. Snowmelt studies carried on in the laboratory and at a field site in Logan Canyon indicated that, for the alkaline snow typical of 1982, the first melt fractions had a higher pH (less acidity) than did the bulk snow. The opposite situation is typically found for acid snow. Although no acidity was present, snow pH increased by 13 percent as a result of contact with organic litter on the soil surface of a 22 m, 32 percent slope. The pH increased even more rapidly in a nearby intermittent stream 9to 7.78 at the edge of the snowpack). Difficulties in interpreting the data from the snow cores in this study include the effects of an unusually wet winter, uncharacteristically low levels of industrial activity due to economic factors, uncertainty about the relative amounts of acidity and buffering capacity reaching the sensitive Uintah Mountain watersheds to the east, and failure to distinguish between soil and acid derived sulfates. Analysis of these difficulties suggests taht offsetting factors would tend to cancel effects of precipitation amount during wet-to-normal winters. the remaining factors require additional research

Analog quantum error correction

Quantum error-correction routines are developed for continuous quantum variables such as position and momentum. The result of such analog quantum error correction is the construction of composite continuous quantum variables that are largely immune to the effects of noise and decoherence.Comment: Ten pages, Te