The Effect of Noise-Induced Quantum Coherence in the Intermediate Band Solar Cells

It has been shown that quantum coherence induced by incoherent light can increase the efficiency of solar cells. Here we evaluate the effect of such coherence in the intermediate band solar cells. We first examine a six-level quantum IBSC model and demonstrate by simulation that the maximum of output power in a solar cell with quantum structure increases more than 16 percent in the case of coherence existence. We then propose an IBSC model which can absorb continuous spectra of sunlight and show that the quantum coherence can increase the output power of the cell. For instance, calculations indicate that the coherence makes an increase of about 31% in the maximum output power of a cell that the width of the conduction and intermediate bands are 100 and 10 meV, respectively. Also, our calculations show that the quantum coherence effect is still observed in increasing the solar cell power by expanding the width of the conduction band, although the output power is reduced due to increase in the thermalization loss. However, expanding the width of the intermediate band reduces the coherence effect.

Multi-wave-mixing-induced nonlinear modulation of diffraction peaks in an opto-atomic grating

We propose an atomic model in close-loop configuration, which exhibits controllable symmetric and asymmetric evolution of significantly enhanced diffraction peaks of the weak probe beam in an opto-atomic grating at far-field regime. Such results are obtained by the linear and nonlinear modulation of the intensities of the diffraction peaks as a result of multi-wave-mixing-induced modification of spatially modulated coherence in a closed four-level atomic system. Novelty of the results lies in predicting the diffraction pattern with uniform peak height due to the dominance of the amplitude part of the grating-transfer-function at the condition of exact atom-field resonance, which is unique to the present model. Efficacy of the present scheme is to apply it in producing nonlinear light generated by four-wave-mixing-induced control of spatially modulated coherence effect. The work also finds its importance for its applicability in the field of all-optical devices.

How Furiously Can Colorless Green Ideas Sleep? Sentence Acceptability in Context

We study the influence of context on sentence acceptability. First we compare the acceptability ratings of sentences judged in isolation, with a relevant context, and with an irrelevant context. Our results show that context induces a cognitive load for humans, which compresses the distribution of ratings. Moreover, in relevant contexts we observe a discourse coherence effect that uniformly raises acceptability. Next, we test unidirectional and bidirectional language models in their ability to predict acceptability ratings. The bidirectional models show very promising results, with the best model achieving a new state-of-the-art for unsupervised acceptability prediction. The two sets of experiments provide insights into the cognitive aspects of sentence processing and central issues in the computational modeling of text and discourse.

An Event Related Potentials Study of Semantic Coherence Effect during Episodic Encoding in Schizophrenia Patients

The objective of this electrophysiological study was to investigate the processing of semantic coherence during encoding in relation to episodic memory processes promoted at test, in schizophrenia patients, by using the N400 paradigm. Eighteen schizophrenia patients and 15 healthy participants undertook a recognition memory task. The stimuli consisted of pairs of words either semantically related or unrelated to a given category name (context). During encoding, both groups exhibited an N400 external semantic coherence effect. Healthy controls also showed an N400 internal semantic coherence effect, but this effect was not present in patients. At test, related stimuli were accompanied by an FN400 old/new effect in both groups and by a parietal old/new effect in the control group alone. In the patient group, external semantic coherence effect was associated with FN400, while, in the control group, it was correlated to the parietal old/new effect. Our results indicate that schizophrenia patients can process the contextual information at encoding to enhance familiarity process for related stimuli at test. Therefore, cognitive rehabilitation therapies targeting the implementation of semantic encoding strategies can mobilize familiarity which in turn can overcome the recollection deficit, promoting successful episodic memory performance in schizophrenia patients.