Yazar "Kurt, Arzu" seçeneğine göre listele

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    1Non-Markovian Corrections to Quantum Regression Theorem for the Strong Coupling Spin-Boson Model
    (2020) Kurt, Arzu
    We report the results of an investigation of the effects of non-Markovian corrections to the dynamics of two-time correlation functions of the strong interaction spin-boson model. Beyond quantum regression theorem corrections are taken into account at the low environmental temperatures for a two-level system (TLS) which is in contact with a structured bath. The results indicate that the corrections lead to appreciable (small) quantitative (qualitative) differences for both biased and non-biased TLS settings.Keywords: Quantum regression theorem, open quantum systems, spin-boson model, quantum dynamics, two-time correlation functions
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    Classical memoryless noise-induced maximally discordant mixed separable steady states
    (Elsevier, 2012) Altıntaş, Ferdi; Kurt, Arzu; Eryiğit, Resul
    We have investigated the dynamics of quantum discord and entanglement for two qubits subject to independent global transverse and/or longitudinal memoryless noisy classical fields. Global transverse and/or longitudinal random fields are found to drive the system to maximally discordant mixed separable steady states for suitable initial conditions. Moreover, two independent noises in the system are found to enhance both the steady state randomness and quantum discord in the absence of entanglement for some initial states. (C) 2012 Elsevier B.V. All rights reserved.
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    Dynamics of a spin-boson model with structured spectral density
    (Elsevier Science Bv, 2018) Kurt, Arzu; Eryiğit, Resul
    We report the results of a study of the dynamics of a two-state system coupled to an environment with peaked spectral density. An exact analytical expression for the bath correlation function is obtained. Validity range of various approximations to the correlation function for calculating the population difference of the system is discussed as function of tunneling splitting, oscillator frequency, coupling constant, damping rate and the temperature of the bath. An exact expression for the population difference, for a limited range of parameters, is derived. (C) 2018 Elsevier B.V. All rights reserved.
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    Dynamics of quantum correlations under non-linear non-markovian stochastic disturbances
    (Bolu Abant İzzet Baysal Üniversitesi, 2017) Kurt, Arzu; Eryiğit, Resul
    Bu tezin ana amacı, kuantum bilgisayar ve kuantum bilgi bilimi araştırma konularında gerekli olan üç farklı problem için tam analitik çözümlerinin elde edilmesidir. Birinci problem, periyodik dış alan tarafından sürülen iki etkileşen kübitin dinamiğiyle ilgilidir. Bu problemin çözümü, kuantum bilgisayarlarını oluşturan kübitlerin kont-rolü için önemlidir. Problem üç kısımdan oluşmaktadır; birinci adımda, bir harmonik alan tarafından sürülen tek bir kübitin dinamiğini araştırdık ve Magnus açılımının, sistemin tam dinamiği için yineleme bağlantılarını türetmek üzere kullanılabilir olduğunu gösterdik. İkinci adım olarak, bir harmonik alan tarafından sürülen iki etkileşmeyen kübit için analitik olası genliklerini elde etmek üzere Bellomo metodunu kullandık. Sürülen etkileşen iki kübitin dinamiği için üçüncü mertebeden diferansiyel denklemler elde ettik ki bu problemin son kısmını oluşturmaktadır. İkinci problem, Krylov ortalama metodunu kullanarak siyah cisim ışıması alanı altında bir yüklü harmonik salınıcının ana denklemi için dördüncü mertebeden terimlerinin doğrulaması ile ilgilidir. Bu sistemin yoğunluk matrisinin dinamiğini tanımlayan kuantum ana denklemi sıklıkla etkileşme parametresinin ikinci mertebesinde yazılır ve ilgili sistem paramet-releri için böyle bir yaklaşımın geçerlilik aralığını belirlemek, bu denklemi çözerek elde edilen dinamiğinin doğruluğunu değerlendirmek için çok önemlidir. Üçüncü ve dördüncü dereceden katkıların çuğunlukla zıt işaretli olduğunu ve yüklü harmonik salınıcı + siyah cisim ışıması alan sistemi için birbirlerini yok ettiklerini gösterdik. Üçüncü problem fizik, kimya ve biyoloji alanlarında birçok olguyu modellemekte kullanılan spin-bozon modelinin dinamiğiyle ilgilidir. Bu problemin birinci kısmı olarak, hem süperiletken kübit hem de biyolojik ışık depolama sistemlerindeki çevreyi tarif etmek için kullanılan bir yapısal spektral yoğunluklu spin-bozon sistemlerin dinamiğini inceledik. Çevresel korelasyon fonksiyonları için tam analitik ifadeleri bulduk ve böyle bir sistemin populasyon dinamiği için tam ifadelerini türettik. Spin-bozon modelin dinamiği konusundaki çalışmanın ikinci kısmı olarak, bir termal çevre içindeki bir kübitin populasyon ve eşuyumluluğu üzerine kübit geçiş frekansındaki iki değerlikli gürültünün etkisini inceledik. Yüksek ve düşük sıcaklık limitlerinde, polaron dönüşüm formülleme içindeki Markovian olmayan ana denklem yaklaşımını kullanarak, eşuyumluluk azalması ve geciş oranlarının analitik ifadelerini elde ettik. Ara ve güçlü etkileşim, düşük sıcaklık ve aşırı sönüm durumunda, gürültünün geçiş oranı üzerinde yapıcı bir rolunun olması bu çalışmanın dikkat çekici bir sonucudur.
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    Effect of classical noise on quantum correlations
    (Bolu Abant İzzet Baysal Üniversitesi, 2013) Kurt, Arzu; Eryiğit, Resul
    Bu tezde iki kubitten oluşan bir sisteme z-yönünde sabit, x-y düzleminde zamana bağımlı iki magnetik alan uygulandığında bu iki kubit arasında oluşan kuantum bağlantıların dinamiği çalışıldı. Çalışma kapsamında özelikle her iki magnetik alan büyüklüğündeki gürültülerin etkisi ve bu gürültülerin korelasyon yaratma kapasitesi üzerinde duruldu. Kuantum bağlantılar olarak kuantum anlaşmazlık ve kuantum dolaşıklık kavramları üzerinde duruldu. Başlangıçta iki kubit arasında hiç bir korelasyon olmasa bile çeşitli gürültü kombinasyonları altında, uzun zaman limitinde azami kuantum anlaşmazlıklı karışım durumların elde edilebileceği gösterildi. Gürültünün kuantum korelasyonlar için yıkıcı etkisi olması beklendiğinden bu bulgu önemli bulundu.
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    Efficient quantum transport in a multi-site system combining classical noise and quantum baths
    (Iop Publishing Ltd, 2020) Kurt, Arzu; Rossi, Matteo A. C.; Piilo, Jyrki
    We study the population dynamics and quantum transport efficiency of a multi-site dissipative system driven by a random telegraph noise (RTN) by using a variational polaron master equation for both linear chain and ring configurations. By using two different environment descriptions-RTN only and a thermal bath+RTN-we show that the presence of the classical noise has a non-trivial role on quantum transport. We observe that there exist large areas of parameter space where the combined bath+RTN influence is clearly beneficial for populating the target state of the transport, and for average trapping time and transport efficiency when accounting for the presence of the reaction center via the use of the sink. This result holds for both of the considered intra-site coupling configurations including a chain and ring. In general, our formalism and achieved results provide a platform for engineering and characterizing efficient quantum transport in multi-site systems both for realistic environments and engineered systems.
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    Fourth-order master equation for a charged harmonic oscillator interacting with the electromagnetic field
    (Elsevier Science Bv, 2015) Kurt, Arzu; Eryiğit, Resul
    The master equation for a charged harmonic oscillator coupled to an electromagnetic reservoir is investigated up to fourth order in the interaction strength by using Krylov averaging method. The interaction is in the velocity-coupling form and includes a diamagnetic term. Exact analytical expressions for the second-, the third-, and the fourth-order contributions to mass renormalization, decay constant, normal and anomalous diffusion coefficients are obtained for the blackbody type environment. It is found that, generally, the third- and the fourth-order contributions have opposite signs when their magnitudes are comparable to that of the second-order one. (C) 2015 Elsevier B.V. All rights reserved.
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    Interplay between non-markovianity of noise and dynamics in quantum systems
    (MDPI, 2023) Kurt, Arzu
    The non-Markovianity of open quantum system dynamics is often associated with the bidirectional interchange of information between the system and its environment, and it is thought to be a resource for various quantum information tasks. We have investigated the non-Markovianity of the dynamics of a two-state system driven by continuous time random walk-type noise, which can be Markovian or non-Markovian depending on its residence time distribution parameters. Exact analytical expressions for the distinguishability as well as the trace distance and entropy-based non-Markovianity measures are obtained and used to investigate the interplay between the non-Markovianity of the noise and that of dynamics. Our results show that, in many cases, the dynamics are also non-Markovian when the noise is non-Markovian. However, it is possible for Markovian noise to cause non-Markovian dynamics and for non-Markovian noise to cause Markovian dynamics but only for certain parameter values.
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    Noise-induced non-Markovianity
    (Amer Physical Soc, 2018) Kurt, Arzu; Eryiğit, Resul
    We have studied the non-Markovianity of a dichotomously driven spin-boson model in the strong-coupling regime in both memory kernel and time convolutionless master-equation formulations. A strong correlation between the decay time of the environmental correlation function and the nonzero non-Markovianity is found in the absence of the external noise. Stochastic driving is shown to create strong non-Markovianity when the dynamics of the system without driving is Markovian. Also, exact analytical expressions for the trace distance distinguishability and the non-Markovianity were obtained for the certain range of the parameters that describe the system and its environment.
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    Quantum coherence and non-Markovianity in a noisy quantum tunneling problem
    (Springer, 2023) Mahdi, Nisreen Mohammed; Kurt, Arzu; Altıntaş, Ferdi
    We investigate the coherence and non-Markovianity of a quantum tunneling system whose barrier is fluctuated by a telegraph noise, and its energy gap is modulated by Gaussian noise. With the help of averaging method, the system dynamics are analytically derived, and the analytical expression for coherence measure and non-Markovianity, focusing on a narrow range of parameter regimes for both initially coherent and non-coherent states are obtained. We observe non-Markovian dynamics in a situation where the Kubo number is high. It is also found that there is no strong relation between the coherence of the system and non-Markovian dynamics except a region in which these two tend to change their behavior at the intermediate noise color for two initial states.
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    Quantum transport efficiency in noisy random-removal and small-world networks
    (IOP Publishing Ltd, 2023) Kurt, Arzu; Rossi, Matteo A. C.; Piilo, Jyrki
    We report the results of an in-depth study of the role of graph topology on quantum transport efficiency in random removal and Watts-Strogatz networks. By using four different environmental models-noiseless, driven by classical random telegraph noise (RTN), thermal quantum bath, and bath + RTN-we compare the role of the environment and of the change in network topology in determining the quantum transport efficiency. We find that small and specific changes in network topology is more effective in causing large change in efficiency compared to that achievable by environmental manipulations for both network classes. Furthermore, we have found that noise dependence of transport efficiency in Watts-Strogatz networks can be categorized into six classes. In general, our results highlight the interplay that network topology and environment models play in quantum transport, and pave the way for transport studies for networks of increasing size and complexity-when going beyond so far often used few-site transport systems.
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    Two-time correlation functions beyond quantum regression theorem: Effect of external noise
    (Springer, 2021) Kurt, Arzu
    We present the results of a study of the two-time correlation functions of a dichotomously driven two-level system in contact with a thermal bath by using corrections beyond the quantum regression theorem. In the strong system-environment coupling regime, it is found that the noise parameters could be tuned to control the magnitude of corrections at low environmental temperatures. Motional averaging and narrowing effect of the external noise were observed on the absorption and emission spectra of the two-state system. Furthermore, effects similar to the destruction of tunneling and noise enhancement of transport are observed in the dynamics of the two-time correlations.