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Yayın Comments on "upper cutoff frequency of the bound wave and new leaky wave on the slotline"(IEEE-INST Electrical Electronics Engineers Inc, 1999-05) İdemen, Mehmet Mithat; Büyükaksoy, İbrahim Alinur[No abstract available]Yayın Preparing multipartite entangled spin qubits via pauli spin blockade(Nature Research, 2020-02-26) Buğu, Sinan; Özaydın, Fatih; Ferrus, Thierry; Kodera, TetsuoPreparing large-scale multi-partite entangled states of quantum bits in each physical form such as photons, atoms or electrons for each specific application area is a fundamental issue in quantum science and technologies. Here, we propose a setup based on Pauli spin blockade (PSB) for the preparation of large-scale W states of electrons in a double quantum dot (DQD). Within the proposed scheme, two W states of n and m electrons respectively can be fused by allowing each W state to transfer a single electron to each quantum dot. The presence or absence of PSB then determines whether the two states have fused or not, leading to the creation of a W state of n + m ? 2 electrons in the successful case. Contrary to previous works based on quantum dots or nitrogen-vacancy centers in diamond, our proposal does not require any photon assistance. Therefore the ‘complex’ integration and tuning of an optical cavity is not a necessary prerequisite. We also show how to improve the success rate in our setup. Because requirements are based on currently available technology and well-known sensing techniques, our scheme can directly contribute to the advances in quantum technologies and, in particular in solid state systems.Yayın Surpassing the classical limit in magic square game with distant quantum dots coupled to optical cavities(Nature Research, 2020-12-17) Buğu, Sinan; Özaydın, Fatih; Kodera, TetsuoThe emergence of quantum technologies is heating up the debate on quantum supremacy, usually focusing on the feasibility of looking good on paper algorithms in realistic settings, due to the vulnerability of quantum systems to myriad sources of noise. In this vein, an interesting example of quantum pseudo-telepathy games that quantum mechanical resources can theoretically outperform classical resources is the Magic Square game (MSG), in which two players play against a referee. Due to noise, however, the unit winning probability of the players can drop well below the classical limit. Here, we propose a timely and unprecedented experimental setup for quantum computation with quantum dots inside optical cavities, along with ancillary photons for realizing interactions between distant dots to implement the MSG. Considering various physical imperfections of our setup, we first show that the MSG can be implemented with the current technology, outperforming the classical resources under realistic conditions. Next, we show that our work gives rise to a new version of the game. That is, if the referee has information on the physical realization and strategy of the players, he can bias the game through filtered randomness, and increase his winning probability. We believe our work contributes to not only quantum game theory, but also quantum computing with quantum dots.Yayın A parallel implementation: Real space Green's function technique(Sage Publications, 2007-04) Onat, Berk; Durukanoğlu, Sondan; Dağ, HasanWe develop an MPI-based parallel algorithm to implement the real space Green's function technique for calculating the vibrational density of states corresponding to a solid. The Hamiltonian describing the interactions between the atoms within the system is obtained from the embedded atom method. The parallel implementation speeds up calculation by an order of magnitude. The parallel implementation details and results are presented in this paper.Yayın NFC internal: An indoor navigation system(MDPI AG, 2015-04) Özdenizci Köse, Büşra; Coşkun, Vedat; Ok, KeremIndoor navigation systems have recently become a popular research field due to the lack of GPS signals indoors. Several indoors navigation systems have already been proposed in order to eliminate deficiencies; however each of them has several technical and usability limitations. In this study, we propose NFC Internal, a Near Field Communication (NFC)-based indoor navigation system, which enables users to navigate through a building or a complex by enabling a simple location update, simply by touching NFC tags those are spread around and orient users to the destination. In this paper, we initially present the system requirements, give the design details and study the viability of NFC Internal with a prototype application and a case study. Moreover, we evaluate the performance of the system and compare it with existing indoor navigation systems. It is seen that NFC Internal has considerable advantages and significant contributions to existing indoor navigation systems in terms of security and privacy, cost, performance, robustness, complexity, user preference and commercial availability.Yayın Numerical calculations of relativistic electron drift loss effect(Amer Geophysical Union, 2008-09-09) Kim, Kyung Chan; Lee, Daeyoung; Kim, Heejeong; Lyons, Larry R.; Lee, Ensang; Öztürk, Mehmet Kaan; Choi, CheongrimIt has been suggested that drift loss to the magnetopause can be one of the major loss mechanisms contributing to relativistic electron flux dropouts. In this study, we examine details of relativistic electrons' drift physics to determine the extent to which the drift loss through the magnetopause is important to the total loss of the outer radiation belt. We have numerically computed drift paths of relativistic electrons' guiding center for various pitch angles, various measurement positions, and different solar wind conditions using the Tsyganenko T02 model. We specifically demonstrate how the drift loss effect depends on these various parameters. Most importantly, we present various estimates of relative changes of the omnidirectional flux of 1 MeV electrons between two different solar wind conditions based on a simple form of the directional flux function. For a change of the dynamic pressure from 4 nPa to 10 nPa with a fixed IMF B-Z = 0 nT, our estimate indicates that after this increase in pressure, the equatorial omnidirectional flux at midnight near geosynchronous altitude decreases by similar to 56 to similar to 97%, depending on the specific pitch angle dependence of the directional flux. The effect rapidly decreases at regions earthward of geosynchronous orbit and shows a general trend of decrease away from midnight. For a change of the IMF BZ from 0 nT to -15 nT with a fixed dynamic pressure of 4 nPa, the relative decrease of the omnidirectional flux at geosynchronous altitude on the nightside is much smaller than that for the pressure increase, but its effect becomes substantial only beyond geosynchronous orbit. Possibilities exist that our results may change to some extent for a different magnetospheric model than the one used here.Yayın Quantum metrology: Surpassing the shot-noise limit with Dzyaloshinskii-Moriya interaction(Nature Publishing Group, 2015-11-09) Özaydın, Fatih; Altıntaş, Azmi AliEntanglement is at the heart of quantum technologies such as quantum information and quantum metrology. Providing larger quantum Fisher information (QFI), entangled systems can be better resources than separable systems in quantum metrology. However the effects on the entanglement dynamics such as decoherence usually decrease the QFI considerably. On the other hand, Dzyaloshinskii-Moriya (DM) interaction has been shown to excite entanglement. Since an increase in entanglement does not imply an increase in QFI, and also there are cases where QFI decreases as entanglement increases, it is interesting to study the influence of DM interaction on quantum metrology. In this work, we study the QFI of thermal entanglement of two-qubit and three-qubit Heisenberg models with respect to SU(2) rotations. We show that even at high temperatures, DM interaction excites QFI of both ferromagnetic and antiferromagnetic models. We also show that QFI of the ferromagnetic model of two qubits can surpass the shot-noise limit of the separable states, while QFI of the antiferromagnetic model in consideration can only approach to the shot-noise limit. Our results open new insights in quantum metrology with Heisenberg models.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 Bifurcation of drift shells near the dayside magnetopause(Amer Geophysical Union, 2007-07-10) Öztürk, Mehmet Kaan; Wolf, Richard A.Close to the dayside magnetopause, there is a region of space where each field line has two magnetic field minima, one near each cusp. That region is located around local noon, and extends about 1-2 R-e from the magnetopause. Particles that enter this region with equatorial pitch angles sufficiently close to 90 degrees will cross the dayside not along an equatorial path, but along one of the two branches on either side of the equatorial plane. The two branches are joined again past local noon. This process of drift-shell bifurcation (DSB) is nonadiabatic even under static conditions. Two physical mechanisms can cause this nonadiabaticity: one that is operative for nearly all magnetospheric magnetic field configurations and another that depends on a particular combination of north-south and east-west asymmetry in the magnetic field. This paper deals only with the first mechanism. For configurations with north-south and east-west symmetry, DSB changes the second invariant I of the motion by a small amount that is of the order of the gyroradius (the first invariant is intact). For near-equatorial particles (I approximate to 0) the change can be significantly larger. Assuming north-south and dawn-dusk symmetry, we present general theoretical expressions for the second-invariant jump Delta I, which can be applied to a variety of magnetic field models. The results show that Delta I is sensitively dependent on the bounce phase of the particle at the bifurcation line. The RMS value of Delta I over a bounce-phase ensemble increases with decreasing mirror field and with increasing kinetic energy. We verify these results with test-particle simulations using model magnetic fields.Yayın Analysis of entanglement measures and LOCC maximized quantum fisher information of general two qubit systems(Nature Publishing Group, 2014-06-24) Erol, Volkan; Özaydın, Fatih; Altıntaş, Azmi AliEntanglement has been studied extensively for unveiling the mysteries of non-classical correlations between quantum systems. In the bipartite case, there are well known measures for quantifying entanglement such as concurrence, relative entropy of entanglement (REE) and negativity, which cannot be increased via local operations. It was found that for sets of non-maximally entangled states of two qubits, comparing these entanglement measures may lead to different entanglement orderings of the states. On the other hand, although it is not an entanglement measure and not monotonic under local operations, due to its ability of detecting multipartite entanglement, quantum Fisher information (QFI) has recently received an intense attraction generally with entanglement in the focus. In this work, we revisit the state ordering problem of general two qubit states. Generating a thousand random quantum states and performing an optimization based on local general rotations of each qubit, we calculate the maximal QFI for each state. We analyze the maximized QFI in comparison with concurrence, REE and negativity and obtain new state orderings. We show that there are pairs of states having equal maximized QFI but different values for concurrence, REE and negativity and vice versa.
