Signatures of Bloch-band geometry on excitons: non-hydrogenic spectra in transition metal dichalcogenides

The geometry of electronic bands in a solid can drastically alter single-particle charge and spin transport. We show here that collective optical excitations arising from Coulomb interactions also exhibit unique signatures of Berry curvature and quantum geometric tensor. A non-zero Berry curvature mixes and lifts the degeneracy of $l \neq 0$ states, leading to a time-reversal-symmetric analog of the orbital Zeeman effect. The quantum geometric tensor, on the other hand, leads to $l$-dependent shifts of exciton states that is analogous to the Lamb shift. Our results provide an explanation of the non-hydrogenic exciton spectrum recently calculated for transition metal dichalcogenides. Numerically, we find a Berry curvature induced splitting of $\sim 10$ meV between the $2p_x \pm i2p_y$ states of WSe$_2$.Comment: 5 pages, 2 figure

Interaction-induced photon blockade using an atomically thin mirror embedded in a microcavity

Narrow dark resonances associated with electromagnetically induced transparency play a key role in enhancing photon-photon interactions. The schemes realized to date relied on the existence of long-lived atomic states with strong van der Waals interactions. Here, we show that by placing an atomically thin semiconductor with ultra-fast radiative decay rate inside a \textcolor{black}{0D} cavity, it is possible to obtain narrow dark or bright resonances in transmission whose width could be much smaller than that of the cavity and bare exciton decay rates. While breaking of translational invariance places a limit on the width of the dark resonance width, it is possible to obtain a narrow bright resonance that is resilient against disorder by tuning the cavity away from the excitonic transition. Resonant excitation of this bright resonance yields strong photon antibunching even in the limit where the interaction strength is arbitrarily smaller than the non-Markovian disorder broadening and the radiative decay rate of the bare exciton. Our findings suggest that atomically thin semiconductors could pave the way for realization of strongly interacting photonic systems in the solid-state.Comment: 4 pages, 3 figures, Comments welcom

All-Optical Manipulation of Electron Spins in Carbon-Nanotube Quantum Dots

We demonstrate theoretically that it is possible to manipulate electron or hole spins all optically in semiconducting carbon nanotubes. The scheme that we propose is based on the spin-orbit interaction that was recently measured experimentally; we show that this interaction, together with an external magnetic field, can be used to achieve optical electron-spin state preparation with a fidelity exceeding 99%. Our results also imply that it is possible to implement coherent spin rotation and measurement using laser fields linearly polarized along the nanotube axis, as well as to convert spin qubits into time-bin photonic qubits. We expect that our findings will open up new avenues for exploring spin physics in one-dimensional systems

Realization of a cascaded quantum system: heralded absorption of a single photon qubit by a single-electron charged quantum dot

Photonic losses pose a major limitation for implementation of quantum state transfer between nodes of a quantum network. A measurement that heralds successful transfer without revealing any information about the qubit may alleviate this limitation. Here, we demonstrate heralded absorption of a single photonic qubit generated by a single neutral quantum dot, by a single-electron charged quantum dot that is located 5 meters away. The transfer of quantum information to the spin degree of freedom takes place upon emission of a photon: for a properly chosen or prepared quantum dot, detection of this photon yields no information about the qubit. We show that this process can be combined with local operations optically performed on the destination node, by measuring classical correlations between the absorbed photon color and the final state of the electron spin. Our work suggests alternative avenues for realization of quantum information protocols based on cascaded quantum systems

INVESTIGATION OF QUALITY OF LIFE ACCORDING TO THE EXERCISE BEHAVIOUR CHANGE STAGES OF WOMEN STUDYING AT UNIVERSITY

The aim of the study was the investigation of Quality of life according to the exercise behaviour change stages of women studying at university. 698 university students, who study in different departments, participated in the study. Quality of life and change in exercise behaviour survey were applied. One way ANOVA, LSD test and Student - t test were used in the study. The average age of University women was 27.50 years. In this study, physical health score, psychological health score, social health score and environmental scores vary according to the health status indicated by the students (p<0.05). In this study, in the case of physical health, the scores of those who are at the stage of Pre-contemplation and Contemplation are significantly lower than those of the students who are at the stage of Taking Action and Maintenance (p<0.05). In the case of psychological health, the scores of those who are at the stage of Pre-contemplation and Contemplation are significantly lower than those of the students who are at the Maintenance stage (p<0.05). In the case of social health, the scores of those who are at the stage of Pre-contemplation and Contemplation are significantly lower than those of the students who are in the preparation, Taking Action and Maintenance (p<0.05). In the case of environmental score, the scores of those who are at the Pre-contemplation stage are significantly lower than those of the students who are at the Maintenance stage (p<0.05). In conclusion, the perceived quality of life of University women according to their exercise behavior change stages were high before the tendency and low during the exercise but quality of life scores increased during continuity. Sedentary women should increase the percentage of continuity in exercise behaviors steps to improve quality of life. Quality of life level according to exercise behavior change stages should be investigated in a large number of women in different universities in Turkey and they should be orientated on exercise planning.  Article visualizations

Observation of dressed excitonic states in a single quantum dot

We report the observation of dressed states of a quantum dot. The optically excited exciton and biexciton states of the quantum dot are coupled by a strong laser field and the resulting spectral signatures are measured using differential transmission of a probe field. We demonstrate that the anisotropic electron-hole exchange interaction induced splitting between the x- and y-polarized excitonic states can be completely erased by using the AC-Stark effect induced by the coupling field, without causing any appreciable broadening of the spectral lines. We also show that by varying the polarization and strength of a resonant coupling field, we can effectively change the polarization-axis of the quantum dot