Dynamics of Global Entanglement under Decoherence

We investigate the dynamics of global entanglement, the Meyer-Wallach measure, under decoherence, analytically. We study two important class of multi-partite entangled states, the Greenberger-Horne-Zeilinger and the W state. We obtain exact results for various models of system-environment interactions (decoherence). Our results shows distinctly different scaling behavior for these initially entangled states indicating a relative robustness of the W state, consistent with previous studies.Comment: 5 pages and 5 figure

Multi-partite entanglement and quantum phase transition in the one-, two-, and three-dimensional transverse field Ising model

In this paper we consider the quantum phase transition in the Ising model in the presence of a transverse field in one, two and three dimensions from a multi-partite entanglement point of view. Using \emph{exact} numerical solutions, we are able to study such systems up to 25 qubits. The Meyer-Wallach measure of global entanglement is used to study the critical behavior of this model. The transition we consider is between a symmetric GHZ-like state to a paramagnetic product-state. We find that global entanglement serves as a good indicator of quantum phase transition with interesting scaling behavior. We use finite-size scaling to extract the critical point as well as some critical exponents for the one and two dimensional models. Our results indicate that such multi-partite measure of global entanglement shows universal features regardless of dimension $d$. Our results also provides evidence that multi-partite entanglement is better suited for the study of quantum phase transitions than the much studied bi-partite measures.Comment: 7 pages, 8 Figures. To appear in Physical Review

Vibration-enhanced quantum transport

In this paper, we study the role of collective vibrational motion in the phenomenon of electronic energy transfer (EET) along a chain of coupled electronic dipoles with varying excitation frequencies. Previous experimental work on EET in conjugated polymer samples has suggested that the common structural framework of the macromolecule introduces correlations in the energy gap fluctuations which cause coherent EET. Inspired by these results, we present a simple model in which a driven nanomechanical resonator mode modulates the excitation energy of coupled quantum dots and find that this can indeed lead to an enhancement in the transport of excitations across the quantum network. Disorder of the on-site energies is a key requirement for this to occur. We also show that in this solid state system phase information is partially retained in the transfer process, as experimentally demonstrated in conjugated polymer samples. Consequently, this mechanism of vibration enhanced quantum transport might find applications in quantum information transfer of qubit states or entanglement.Comment: 7 pages, 6 figures, new material, included references, final published versio

Quantum transport in quantum networks and photosynthetic complexes at the steady state

Recently, several works have analysed the efficiency of photosynthetic complexes in a transient scenario and how that efficiency is affected by environmental noise. Here, following a quantum master equation approach, we study the energy and excitation transport in fully connected networks both in general and in the particular case of the Fenna-Matthew-Olson complex. The analysis is carried out for the steady state of the system where the excitation energy is constantly "flowing" through the system. Steady state transport scenarios are particularly relevant if the evolution of the quantum system is not conditioned on the arrival of individual excitations. By adding dephasing to the system, we analyse the possibility of noise-enhancement of the quantum transport.Comment: 10 pages, single column, 6 figures. Accepted for publication in Plos On

Motional effects on the efficiency of excitation transfer

Energy transfer plays a vital role in many natural and technological processes. In this work, we study the effects of mechanical motion on the excitation transfer through a chain of interacting molecules with application to biological scenarios of transfer processes. Our investigation demonstrates that, for various types of mechanical oscillations, the transfer efficiency is significantly enhanced over that of comparable static configurations. This enhancement is a genuine quantum signature, and requires the collaborative interplay between the quantum-coherent evolution of the excitation and the mechanical motion of the molecules; it has no analogue in the classical incoherent energy transfer. This effect may not only occur naturally, but it could be exploited in artificially designed systems to optimize transport processes. As an application, we discuss a simple and hence robust control technique.Comment: 25 pages, 11 figures; completely revised; version accepted for publicatio

Evaluation of right ventricular function and various models of delayed enhancement with cardiac magnetic resonance imaging in patients with repaired tetralogy of fallot

Background: Tetralogy of Fallot (TOF) is considered as the most frequent cyanotic congenital heart disorder. Right ventricular (RV) dysfunction is possible to be observed in patients with repaired TOF. Delayed enhancement (DE) is one of the recommended findings for RV dysfunction. Objectives: This study aimed at investigating the DE and its probable relationship with RV function through cardiac magnetic resonance (CMR). Patients and Methods: In this cross-sectional study, the values of cardiovascular magnetic resonance of 110 symptomatic patients, who had repaired TOF for 35 years, were gathered. We compared cardiac function indices (CFI) in patients with and without DE. Results: The patients had an average age of 21.93 ± 6.94 years (59.12 were male and 40.94 were female). 93.66 of the subjects showed DE and 6.44 of them did not have DE. 78.61 of the samples had DE of the right ventricular outflow tract (RVOT); whereas, 21.39 showed DE of the other sites. The differences between mean regurgitation fraction, average RV end-diastolic volume (RVEDV), average RV end systolic volume (ESV), and average RV ejection fraction in DE positive and negative patients were statistically significant (P values = 0.01, 0.04, 0.04, and 0.01, respectively.) Conclusion: DE commonly occurs as a complication of surgery to repair TOF and could be used as a factor for impaired RV function and other complications. Using CMR imaging for follow up of these patients could lead to diagnosis of these complications. © 2020, Iranian Journal of Radiology. T

Accuracy and precision of four common peripheral temperature measurement methods in intensive care patients

Simin Asadian,1 Alireza Khatony,1 Gholamreza Moradi,2 Alireza Abdi,1 Mansour Rezaei,3 1Nursing and Midwifery School, Kermanshah University of Medical Sciences, 2Department of Anesthesiology, 3Biostatistics & Epidemiology Department, Kermanshah University of Medical Sciences, Kermanshah, Iran Introduction: An accurate determination of body temperature in critically ill patients is a fundamental requirement for initiating the proper process of diagnosis, and also therapeutic actions; therefore, the aim of the study was to assess the accuracy and precision of four noninvasive peripheral methods of temperature measurement compared to the central nasopharyngeal measurement. Methods: In this observational prospective study, 237 patients were recruited from the intensive care unit of Imam Ali Hospital of Kermanshah. The patients’ body temperatures were measured by four peripheral methods; oral, axillary, tympanic, and forehead along with a standard central nasopharyngeal measurement. After data collection, the results were analyzed by paired t-test, kappa coefficient, receiver operating characteristic curve, and using Statistical Package for the Social Sciences, version 19, software. Results: There was a significant meaningful correlation between all the peripheral methods when compared with the central measurement (P<0.001). Kappa coefficients showed good agreement between the temperatures of right and left tympanic membranes and the standard central nasopharyngeal measurement (88%). Paired t-test demonstrated an acceptable precision with forehead (P=0.132), left (P=0.18) and right (P=0.318) tympanic membranes, oral (P=1.00), and axillary (P=1.00) methods. Sensitivity and specificity of both the left and right tympanic membranes were more than for other methods. Conclusion: The tympanic and forehead methods had the highest and lowest accuracy for measuring body temperature, respectively. It is recommended to use the tympanic method (right and left) for assessing a patient’s body temperature in the intensive care units because of high accuracy and acceptable precision. Keywords: body temperature, thermometers, intensive care units, sensitivity and specificity, tympanic membran