Papers by Keyword: Quantum Coherence

Abstract: One of the most surprising and significant advances in the study of the photosynthetic light-harvesting process is the discovery that the electronic energy transfer (ET) might involve long-lived electronic coherences, also at physiologically relevant conditions. This means that the transfer of energy among different chromophores does not follow the expected classical incoherent hopping mechanism, but that quantum-mechanical laws can steer the migration of energy. The implications of such quantum transport regime, although currently under debate, might have a tremendous impact in our way to think about natural and artificial light-harvesting and suggest new directions for the development of artificial devices for the efficient capture and re-use of solar energy. Central to these discoveries has been the development of new ultrafast spectroscopic techniques, in particular two-dimensional electronic spectroscopy, which is now the primary tool to obtain clear and definitive experimental proof of such effects.

Abstract: Since a two-level resonant atomic system can be simulated by a simple circuit, three- and four-level electromagnetically induced transparency (EIT) that occur due to light-atom interaction can find its classical counterpart in circuit analog. As the optical response of an EIT atomic medium (including atomic vapors and semiconductor-quantum-dot dielectrics) can be controlled via tunable quantum interference induced by applied external control fields, in the scheme of circuit analog, such a controllable manipulation is achieved via capacitor coupling, where two loops are coupled by a capacitor that can represent the applied control fields in atomic EIT. Both numerical simulation and experimental demonstration of three- and four-level EIT were performed based on such a scenario of circuit analog. The classical “coherence” relevant to quantum interference among transitions pathways driven by both probe and control fields in EIT atomic systems has been manifested in the present circuit analog of EIT.

Abstract: The optical response of an atomic vapor can be controlled by using tunable quantum interference induced by external control field. A periodic layered medium whose unit cells consist of dielectric (e.g., GaAs) and EIT (electromagnetically induced transparency) atomic vapor is suggested. It is demonstrated that such an EIT-based periodic layered medium shows more flexible optical response (sensitive to frequency) than a conventional photonic crystal does. The controllable band structure that depends on the external control field can be applicable to designs of new devices such as photonic switches and photonic logic gates, where one laser field can be controlled by the other one, and would have potential applications in the field of integrated optical circuits and other related areas, e.g., the all-optical technique.

Abstract: The signal characteristics of the biophotons from human hands were studied using correlation and δ-value analyses. Three healthy individuals without any history of disease participated in the measurements, six times every Friday for 52 weeks, while staying in a room with dim lighting to eliminate any delayed luminescence caused by the sun or room lights. Two head-on type photomultiplier tubes inside a dark room were used to simultaneously measure the biophoton emissions from the palm and dorsum of the left and right hand with a 100ms gate time. In view of the signal process, a cross-correlation of the long-term data, i.e. the weekly measurements, revealed a strong correlation between the signals from the left and right hand, yet only a very weak correlation between the palm and dorsum. The non-classical light property of the biophotons, that has a quantum coherence nature, was compared with that of the dark counts of the PMTs using a δ- value analysis. The average δ-value for the biophotons was 0.08±0.07. As such, it was found that the palm emissions were very coherent, while the dorsum emissions showed an occasional lack of coherence.