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Yayın Generating multi-atom entangled W states via light-matter interface based fusion mechanism(Nature Publishing Group, 2015-11-09) Özaydın, Fatih; Zang, Xue-Ping; Yang, Ming; Song, Wei; Cao, Zhuo-LiangW state is a key resource in quantum communication. Fusion technology has been proven to be a good candidate for preparing a large-size W state from two or more small-size W states in linear optical system. It is of great importance to study how to fuse W states via light-matter interface. Here we show that it is possible to prepare large-size W-state networks using a fusion mechanism in cavity QED system. The detuned interaction between three atoms and a vacuum cavity mode constitute the main fusion mechanism, based on which two or three small-size atomic W states can be fused into a larger-size W state. If no excitation is detected from those three atoms, the remaining atoms are still in the product of two or three new W states, which can be re-fused. The complicated Fredkin gate used in the previous fusion schemes is avoided here. W states of size 2 can be fused as well. The feasibility analysis shows that our fusion processes maybe implementable with the current technology. Our results demonstrate how the light-matter interaction based fusion mechanism can be realized, and may become the starting point for the fusion of multipartite entanglement in cavity QED system.Yayın Dilemma between security and privacy on the internet(Işık Üniversitesi, 2005-07-31) Ayduran, Güven; Akçakaya, Ergül; Yarman, Bekir Sıddık Binboğa; Işık Üniversitesi, Fen Bilimleri Enstitüsü, Enformasyon Teknolojileri Yüksek Lisans ProgramıIn this thesis, the following issues are discussed. Even in today society, it is hard to talk about security and privacy. And no one can imagine what will be structure of tomorrow society. We study what are the internet security systems and government security projects. Even we discuss that these systems effect to human rights and privacy. We define importance of cryptography and discuss relation with human rights. We examine internet privacy laws. We also study about George Orwell's book '1984' and consider similarity between novel and real life. We give information about intellectual property and its rights on the internet. We show that intellectual property rights are not enough to protect all properties and these rules are valid for some economic environments. We also discuss issue in instead of knowledge society, creates ignorance society. All these discussed and studied issues show big dilemma to us between security and privacy. The dilemma goes to a result that there is no security in today's society. Keywords: Security, privacy, internet security, internet privacy rights, cryptography, Orwell, intellectual property rights, knowledge society, ignorance society, internet and dilemma.Yayın Deterministic generation of large scale atomic W states(Optical Soc Amer, 2016-05-30) Zang, Xue-Ping; Yang, Ming; Özaydın, Fatih; Song, Wei; Cao, Zhuo-LiangWe present a deterministic scheme for generating large-scale atomic W states in a cavity QED system via a simple expansion mechanism, which is realized only by a detuned interaction between two identical atoms and a vacuum cavity mode. With the presented scheme, a W-type Bell pair can be created and an n-atom W state can be expanded to a 2n-atom W state with a unit probability of success in principle. No multi-atom gates, quantum memories or quantum non-demolition measurements are required, greatly simplifying the experimental realization of the scheme. The feasibility analysis shows that our expansion scheme can be implemented with state-of-the-art technologies. Our scheme enables advances not only in quantum information and communication but also in quantum thermodynamics, where atomic W states plays a crucial role.
