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Yayın Deterministic local doubling of W states(OSA - The Optical Society, 2016-11-01) Yeşilyurt, Can; Buğu, Sinan; Özaydın, Fatih; Altıntaş, Azmi Ali; Tame, Mark S.; Yang, Lan; Özdemir, Şahin KayaIn large quantum systems, multipartite entanglement can be found in many inequivalent classes. Preparing states of arbitrary size in different classes is important for performing a wide range of quantum protocols. W states, in particular, constitute a class with a variety of quantum networking protocols. However, all known schemes for preparing polarization encoded photonic W states are probabilistic, with resource requirements increasing at least sub-exponentially. We propose a deterministic scheme for preparing W states of size of any power of 2, which requires no prior entanglement and can be performed locally. We introduce an all-optical setup that can efficiently double the size of W states of arbitrary size. Our scheme advances the use of W states in real-world quantum networks and could be extended to other physical systems.Yayın İki qubit’lik kuantum haberleşme ağlarının eş zamanlılık donanıklık ölçütü ile kuantum Fisher bilgisinin analizi(IEEE, 2014-06-12) Erol, Volkan; Buğu, Sinan; Özaydın, Fatih; Altıntaş, Azmi AliKuantum dolanıklık, kuantum haberleşme mühendisliğinin en temel kavramlarından biridir. Kuantum sistemlerin dolanıklık ölçütlerine göre sıralanması günümüzde oldukça çok çalışılan konulardan birisidir. İki parçacıklı iki seviyeli sistemlerin (qubit) sıralaması konusu, çok bilinen Eş Zamanlılık (Concurrence), Negatiflik (Negativity) ve Dolanıklığın Göreceli Entropisi (REE) ölçütlerine göre çeşitli araştırmacılar tarafından çalışılmıştır[1-5]. Biz bu çalışmada, iki qubit kuantum sistemlerin sıralamasını Kuantum Fisher Bilgisi ve Eş Zamanlılık dolanıklık ölçütünü karşılaştıracak şekilde analiz etmekteyiz. Çalışma özelinde, bin adet rastgele türetilmiş iki qubit sistemin Eş Zamanlılık değerleri hesaplanmakta; elde ettiğimiz bu sonuçların iki qubit sistemlerde Kuantum Fisher Bilgisi ile karşılaştırılması yapılmakta ve aralarındaki ilginç farklar gözlemlenmektedir.Yayın Kübit-Kütrit kuantum haberleşme sistemleri için negatiflik ve dolanıklığın göreceli entropisi ölçütlerinin analizi(IEEE, 2015-06-19) Erol, Volkan; Özaydın, Fatih; Altıntaş, Azmi AliKuantum Bilgi Teorisi ve Kuantum Hesaplama konuları geleceğin bilgisayar teknolojisi olarak nitelendirilen ve çok yüksek hızlarda işlem yapacak olması öngörülen Kuantum Bilgisayarlarının teorik temelini oluşturan oldukça sıcak çalışma alanlarıdır. Kuantum Bilgisayarlarında bilginin taşınacağı birim kübit olarak nitelendirilse de, bazı problemler için bu birimlerin üç seviye (trinary) olan kütritlerce kurgulanabileceği teorik olarak gösterilmiştir. Bu çalışma kapsamında, kübit-kütrit Kuantum Haberleşme Sistemlerinin dolanıklıklığını ölçmek için kullanılan Negatiflik ve Dolanıklığın Göreceli Entropisi ölçütlerinin karşılaştırmalı analizi yapılmıştır. Bu bağlamda, rastgele türetilmiş 1000 adet kübit-kütrit sistem durumlarının adı geçen ölçütleri hesaplanmış ve bu değerler sistem durumlarının sıralanması amacıyla karşılaştırılmıştır. Yapılan analiz kapsamında sistem durumlarının sıralaması problemi açısından oldukça ilginç sonuçlar gözlemlenmiştir.Yayın Enhancing the W state fusion process with a toffoli gate and a CNOT gate via one-way quantum computation and linear optics(Polish Acad Sciences Inst Physics, 2015-04) Diker, Fırat; Özaydın, Fatih; Arık, MetinCreation of large-scale W state quantum networks is a key step for realization of various quantum information tasks. Regarding the photonics technology, a simple optical setup was proposed for the fusion of two W states. Recently it was shown that via a single Fredkin gate, this basic so-called "fusion setup" can be enhanced. However the main problem was that the probability of success of realization of Fredkin gate with linear optics is too low. In this work, we show that the same enhancement can be made possible via one Toffoli and one CNOT gate, instead of a Fredkin gate. Not only the probability of success of the combination of these two gates is much higher, than that of a single Fredkin gate via linear optics, but also there is another method for implementing our setup with current photonics technology, almost with a unity success probability: A hybrid circuit consisting of a Toffoli gate which can be implemented via one-way quantum computation on a weighted graph state of 8 qubits with a unity success probability and a linear optical CNOT gate which has a success probability close to unity. Therefore the preparation of polarization based encoded multi particle entangled W states of arbitrary sizes becomes considerably more efficient.Yayın An optical setup for deterministic creation of four Partite W state(Polish Academy of Sciences, 2015-04) Yeşilyurt, Can; Buğu, Sinan; Diker, Fırat; Altıntaş, Azmi Ali; Özaydın, FatihIn order to create polarization based entanglement networks of W-4 state, we propose an optical setup, which uses only four horizontally polarized photons as resource which implies no entanglement requirement as a resource. This setup can generate target state deterministically, by operating several quantum optical gates, which can be realized with current photonics technology. The setup we propose is composed of one Not, two Hadamard, five Controlled Not (CNot) and one Toffoli gate.Yayın Temperature control in dissipative cavities by entangled dimers(Amer Chemical Soc, 2019-02-21) Dağ, Ceren B.; Niedenzu, Wolfgang; Özaydın, Fatih; Müstecaplıoğlu, Özgür Esat; Kurizki, GershonWe show that the temperature of a cavity field can be drastically varied by its interaction with suitably entangled atom pairs (dimers) traversing the cavity under realistic atomic decoherence. To this end we resort to the hitherto untapped resource of naturally entangled dimers whose state can be simply controlled via molecular dissociation, collisions forming the dimer, or unstable dimers such as positronium. Depending on the chosen state of the dimer, the cavity-field mode can be driven to a steady-state temperature that is either much lower or much higher than the ambient temperature, despite adverse effects of cavity loss and atomic decoherence. Entangled dimers enable much broader range of cavity temperature control than single "phaseonium" atoms with coherently superposed levels. Such dimers are shown to constitute highly caloric fuel that can ensure high efficiency or power in photonic thermal engines. Alternatively, they can serve as controllable thermal baths for quantum simulation of energy exchange in photosynthesis or quantum annealing.Yayın Parameter estimation with Dzyaloshinskii–Moriya interaction under external magnetic fields(Springer, 2020-02-01) Özaydın, Fatih; Altıntaş, Azmi AliWe study the effects of external magnetic fields on the precision of parameter estimation with thermal entanglement of two spins in XX model, in the presence of Dzyaloshinskii–Moriya (DM) interaction. Although DM interaction excites but external magnetic fields usually decrease quantum mechanical properties of spin systems such as entanglement, we show by calculating the quantum Fisher information that not only DM interaction D but also homogeneous magnetic field B can increase the precision of parameter estimation, overwhelming the destructive effects of thermalization. We also show that inhomogeneous magnetic field b increases (decreases) the precision of parameter estimation if it is less (greater) than D. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.Yayın Engineering four-qubit fuel states for protecting quantum thermalization machine from decoherence(Multidisciplinary Digital Publishing Institute (MDPI), 2024-01-10) Özaydın, Fatih; Sarkar, Ramita; Bayrakçı, Veysel; Bayındır, Cihan; Altıntaş, Azmi Ali; Müstecaplıoğlu, Özgür E.Decoherence is a major issue in quantum information processing, degrading the performance of tasks or even precluding them. Quantum error-correcting codes, creating decoherence-free subspaces, and the quantum Zeno effect are among the major means for protecting quantum systems from decoherence. Increasing the number of qubits of a quantum system to be utilized in a quantum information task as a resource expands the quantum state space. This creates the opportunity to engineer the quantum state of the system in a way that improves the performance of the task and even to protect the system against decoherence. Here, we consider a quantum thermalization machine and four-qubit atomic states as its resource. Taking into account the realistic conditions such as cavity loss and atomic decoherence due to ambient temperature, we design a quantum state for the atomic resource as a classical mixture of Dicke and W states. We show that using the mixture probability as the control parameter, the negative effects of the inevitable decoherence on the machine performance almost vanish. Our work paves the way for optimizing resource systems consisting of a higher number of atoms.Yayın Superactivating bound entanglement in quantum networks via quantum Zeno dynamics and a novel algorithm for optimized Zeno evolution(MDPI, 2023-01) Özaydın, Fatih; Bayrakçı, Veysel; Altıntaş, Azmi Ali; Bayındır, CihanAn arbitrary amount of entanglement shared among nodes of a quantum network might be nondistillable if the nodes lack the information on the entangled Bell pairs they share. Making such a system distillable, which is called the superactivation of bound entanglement (BE), was shown to be possible through systematic quantum teleportation between the nodes, requiring the implementation of controlled-gates scaling with the number of nodes. In this work, we show in two scenarios that the superactivation of BE is possible if nodes implement the proposed local quantum Zeno strategies based on only single qubit rotations and simple threshold measurements. In the first scenario we consider, we obtain a two-qubit distillable entanglement system as in the original superactivation proposal. In the second scenario, we show that superactivation can be achieved among the entire network of eight qubits in five nodes. In addition to obtaining all-particle distillable entanglement, the overall entanglement of the system in terms of the sum of bipartite cuts is increased. We also design a general algorithm with variable greediness for optimizing the QZD evolution tasks. Implementing our algorithm for the second scenario, we show that a significant improvement can be obtained by driving the initial BE system into a maximally entangled state. We believe our work contributes to quantum technologies from both practical and fundamental perspectives bridging nonlocality, bound entanglement and the quantum Zeno dynamics among a quantum network.
