Non-Abelian off-diagonal geometric phases in nano-engineered four-qubit systems

The concept of off-diagonal geometric phase (GP) has been introduced in order to recover interference information about the geometry of quantal evolution where the standard GPs are not well-defined. In this Letter, we propose a physical setting for realizing non-Abelian off-diagonal GPs. The proposed non-Abelian off-diagonal GPs can be implemented in a cyclic chain of four qubits with controllable nearest-neighbor interactions. Our proposal seems to be within reach in various nano-engineered systems and therefore opens up for first experimental test of the non-Abelian off-diagonal GP.Comment: Some changes, journal reference adde

Quantum heat engines with multiferroic working substance

The work provides an overview on some recent advances in the area of quantum thermodynamics and quantum heat engines. A particular emphasis is put on the possibility of constructing finite time quantum cycles and adiabatic shortcuts. We discuss in details the particular quantum heat engines operating with a multiferroic working substance.Comment: Lecture Notes of the 12th International School on Theoretical Physics Symmetry, Spin Dynamics and the Properties of Nanostructure

Antimicrobial effects of chlorhexidine, matrica drop mouthwash (chamomile extract), and normal saline on hospitalized patients with endotracheal tubes

Background: The functions and use of mouthwashes are variable depending on their type. Oral care in patients with endotracheal tubes is important to prevent side effects such as pneumonia. The aim of this study was to determine the antimicrobial effects of chlorhexidine, drop of Matrica mouthwash (chamomile extract), and normal saline on hospitalized patients with endotracheal tube in an intensive care unit (ICU). Materials and Methods: In this clinical trial, 39 patients admitted to the ICU were selected by convenience sampling, were matched based on age and sex, and randomly assigned to three groups (chlorhexidine, Matrica, saline). Mouth washing was performed every 8 to 48 hours. The samples were taken at time zero (before the intervention) and 48 hours after the intervention for bacterial culture. Antibacterial activity of each mouthwash on microorganisms was measured based on the growth of Staphylococcus aureus, Pneumococcal, Enterococcus, Pseudomonas, and Escherichia coli. The obtained data were then analyzed using Chi-square and Fisher's exact tests with the Statistical Package for the Social Sciences Package version 18. Results: Chlorhexidine mouthwash was more effective in preventing colonization of bacteria in the mouth (point probability = 0.06) in comparison with chamomile and saline mouthwashes. Nevertheless, none of the tested mouthwashes were able to remove pathogens, including Staphylococcus aureus, Pseudomonas, Klebsiella, and Acinetobacter. Conclusions: 0.2% chlorhexidine mouthwash has a significant effect on the bacterial colonization rate in comparison with Matrica and normal saline mouthwashes in ICU hospitalized patients with endotracheal tube

Seroprevalence of toxocariasis in children aged 1-9 years in western Islamic Republic of Iran, 2003

We determined the seroprevalence of Toxocara canis infection in 544 children under 10 years randomly selected from urban and rural areas of Hamadan, An enzyme-linked immunosorbent assay was used for detection of antibodies to T. canis excretion - secretion antigens. Using a questionnaire, epidemiological factors associated with infection were examined, including age, sex, residence. Antibodies to T. canis were detected in 29 children (5.3%) and 19 children (3.5%) were categorized as borderline positive; thus together this gave a prevalence of toxocariasis of 8.8%. No significant differences were found in terms of sex, age and residence

Conceptual aspects of geometric quantum computation

Geometric quantum computation is the idea that geometric phases can be used to implement quantum gates, i.e., the basic elements of the Boolean network that forms a quantum computer. Although originally thought to be limited to adiabatic evolution, controlled by slowly changing parameters, this form of quantum computation can as well be realized at high speed by using nonadiabatic schemes. Recent advances in quantum gate technology have allowed for experimental demonstrations of different types of geometric gates in adiabatic and nonadiabatic evolution. Here, we address some conceptual issues that arise in the realizations of geometric gates. We examine the appearance of dynamical phases in quantum evolution and point out that not all dynamical phases need to be compensated for in geometric quantum computation. We delineate the relation between Abelian and non-Abelian geometric gates and find an explicit physical example where the two types of gates coincide. We identify differences and similarities between adiabatic and nonadiabatic realizations of quantum computation based on non-Abelian geometric phases.Comment: Revised version; journal reference adde

Non-Abelian quantum holonomy of hydrogen-like atoms

We study the Uhlmann holonomy [Rep. Math. Phys. 24, 229 (1986)] of quantum states for hydrogen-like atoms where the intrinsic spin and orbital angular momentum are coupled by the spin-orbit interaction and subject to a slowly varying magnetic field. We show that the holonomy for the orbital angular momentum and spin subsystems is non-Abelian, while the holonomy of the whole system is Abelian. Quantum entanglement in the states of the whole system is crucially related to the non-Abelian gauge structure of the subsystems. We analyze the phase of the Wilson loop variable associated with the Uhlmann holonomy, and find a relation between the phase of the whole system with corresponding marginal phases. Based on the result for the model system we provide evidence that the phase of the Wilson loop variable and the mixed-state geometric phase [E. Sj\"oqvist {\it et al.} Phys. Rev. Lett. 85, 2845 (2000)] are in general inequivalent.Comment: Shortened version; journal reference adde