Multiplexed Memory-Insensitive Quantum Repeaters

Long-distance quantum communication via distant pairs of entangled quantum bits (qubits) is the first step towards more secure message transmission and distributed quantum computing. To date, the most promising proposals require quantum repeaters to mitigate the exponential decrease in communication rate due to optical fiber losses. However, these are exquisitely sensitive to the lifetimes of their memory elements. We propose a multiplexing of quantum nodes that should enable the construction of quantum networks that are largely insensitive to the coherence times of the quantum memory elements.Comment: 5 pages, 4 figures. Accepted for publication in PR

Entanglement of light-shift compensated atomic spin waves with telecom light

Entanglement of a 795 nm light polarization qubit and an atomic Rb spin wave qubit for a storage time of 0.1 s is observed by measuring the violation of Bell's inequality (S = 2.65 \pm 0.12). Long qubit storage times are achieved by pinning the spin wave in a 1064 nm wavelength optical lattice, with a magic-valued magnetic field superposed to eliminate lattice-induced dephasing. Four-wave mixing in a cold Rb gas is employed to perform light qubit conversion between near infra red (795 nm) and telecom (1367 nm) wavelengths, and after propagation in a telecom fiber, to invert the conversion process. Observed Bell inequality violation (S = 2.66 \pm 0.09), at 10 ms storage, confirms preservation of memory/light entanglement through the two stages of light qubit frequency conversion.Comment: 5 pages, 3 figure

Modulation of the CD8+-T-cell response by CD4+ CD25+ regulatory T cells in patients with Hepatitis B virus infection

CD4+ CD25+ regulatory T cells have been shown to maintain peripheral tolerance against self and foreign antigens. In this study we analyzed the effect of circulating CD4+ CD25+ T cells on CD8+-T-cell responses of patients with chronic and resolved hepatitis B virus (HBV) infection. We demonstrated that circulating CD4+ CD25+ T cells modulate the function and expansion of HBV-specific CD8+ cells ex vivo in all patients, regardless of whether they have chronic or resolved HBV infection. The possible role of CD4+ CD25+ T cells in the pathogenesis of chronic HBV infection is not supported by these data. However, these results might have implications for optimizing future immunotherapeutic approaches to HBV treatment

The Woods-Saxon Potential in the Dirac Equation

The two-component approach to the one-dimensional Dirac equation is applied to the Woods-Saxon potential. The scattering and bound state solutions are derived and the conditions for a transmission resonance (when the transmission coefficient is unity) and supercriticality (when the particle bound state is at E=-m) are then derived. The square potential limit is discussed. The recent result that a finite-range symmetric potential barrier will have a transmission resonance of zero-momentum when the corresponding well supports a half-bound state at E=-m is demonstrated.Comment: 8 pages, 4 figures. Submitted to JPhys

Perceptions and Attitude of Students toward E-Learning in Kwara State University, Malete, Kwara State, Nigeria

The study examined the perceptions and attitude of students toward e-learning in Kwara State University, Malete, Kwara State, Nigeria. The objectives of the study were to: examine the perceptions of undergraduates on the adoption of e-learning by Kwara State University; examine the attitude of students towards e-learning in Kwara State University, Malete; and investigate the constraints affecting e-learning by students of Kwara State University. The study adopted the survey design. The population of the study comprised the entire undergraduate students in Kwara State University, Malete. 240 students participated in the online survey. A self-designed questionnaire was used for the collection of data. Data were analysed using descriptive statistics of frequency counts and percentage. Findings of the study revealed that students have positive perceptions and attitude toward e-learning. The study also revealed the constraints affecting the use of e-learning tools by students of Kwara State University, Malete. The study recommended that the management of Kwara State University should embraced e-learning as a way of overcoming the covid-19 challenges in the university and expanding learning. Keywords: Attitude, E-learning, Kwara State, Perceptions, Undergraduate students DOI: 10.7176/JEP/11-31-08 Publication date: November 30th 202

Knowledge Sharing Practices among Lecturers in Nigerian Universities: A Case Study

The study investigated knowledge sharing practices among lecturers in Nigerian Universities: A case study of Kwara State University, Malete. The objectives of the study were to: examine the perceptions of lecturers about knowledge sharing; identify the benefits of knowledge sharing among lecturers; identify ways used in sharing knowledge by lecturers; and investigate the barriers militating against knowledge sharing among lecturers. The study adopted the descriptive survey design. The population of the study comprised the entire lecturers in Kwara State University, Malete numbering 413 lecturers. A simple random technique was used to select 217 lecturers from the 7 faculties in the university. A self-designed questionnaire was used for the collection of data. Data were analysed using descriptive statistics of frequency counts and percentage. Findings of the study revealed that lecturers have positive perceptions toward knowledge sharing. It also revealed that there are numerous benefits of sharing knowledge by lecturers. The study further highlighted the various ways of sharing knowledge by lecturers. The study also revealed the barriers militating against knowledge sharing by lecturers in Nigerian universities. It is recommended that university management should create massive campaigns on the need for lecturers to embrace knowledge sharing among peers. This can be done through training, conferences, and seminars etc on the need for knowledge sharing among them. Keywords: knowledge management, knowledge sharing, practices, perceptions DOI: 10.7176/IKM/10-6-06 Publication date:September 30th 202

Scattering of Woods-Saxon Potential in Schrodinger Equation

The scattering solutions of the one-dimensional Schrodinger equation for the Woods-Saxon potential are obtained within the position-dependent mass formalism. The wave functions, transmission and reflection coefficients are calculated in terms of Heun's function. These results are also studied for the constant mass case in detail.Comment: 14 page

New exact solution of the one dimensional Dirac Equation for the Woods-Saxon potential within the effective mass case

We study the one-dimensional Dirac equation in the framework of a position dependent mass under the action of a Woods-Saxon external potential. We find that constraining appropriately the mass function it is possible to obtain a solution of the problem in terms of the hypergeometric function. The mass function for which this turns out to be possible is continuous. In particular we study the scattering problem and derive exact expressions for the reflection and transmission coefficients which are compared to those of the constant mass case. For the very same mass function the bound state problem is also solved, providing a transcendental equation for the energy eigenvalues which is solved numerically.Comment: Version to match the one which has been accepted for publication by J. Phys. A: Math. Theor. Added one figure, several comments and few references. (24 pages and 7 figures

Entanglement of remote atomic qubits

We report observations of entanglement of two remote atomic qubits, achieved by generating an entangled state of an atomic qubit and a single photon at Site A, transmitting the photon to Site B in an adjacent laboratory through an optical fiber, and converting the photon into an atomic qubit. Entanglement of the two remote atomic qubits is inferred by performing, locally, quantum state transfer of each of the atomic qubits onto a photonic qubit and subsequent measurement of polarization correlations in violation of the Bell inequality |S| <2. We experimentally determine S =2.16 +/- 0.03. Entanglement of two remote atomic qubits, each qubit consisting of two independent spin wave excitations, and reversible, coherent transfer of entanglement between matter and light, represent important advances in quantum information science.Comment: 5 pages, 3 figure