Researcher: Çakmak, Barış
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Çakmak, Barış
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Publication Open Access Thermal production, protection, and heat exchange of quantum coherences(American Physical Society (APS), 2017) Department of Physics; Çakmak, Barış; Müstecaplıoğlu, Özgür Esat; Manatuly, A.; Faculty Member; Department of Physics; College of Sciences; N/A; 1674; N/AWe consider finite-sized atomic systems with varying number of particles which have dipolar interactions among them and are also under the collective driving and dissipative effect of a thermal photon environment. Focusing on the simple case of two atoms, we investigate the impact of different parameters of the model on the coherence contained in the system. We observe that, even though the system is initialized in a completely incoherent state, it evolves to a state with a finite amount of coherence and preserves that coherence in the long-time limit in the presence of thermal photons. We propose a scheme to utilize the created coherence in order to change the thermal state of a single two-level atom by having it repeatedly interact with a coherent atomic beam. Finally, we discuss the scaling of coherence as a function of the number of particles in our system up to N = 7.Publication Open Access Spin quantum heat engines with shortcuts to adiabaticity(American Physical Society (APS), 2019) Department of Physics; Müstecaplıoğlu, Özgür Esat; Çakmak, Barış; Faculty Member; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; 1674; 252838We consider a finite-time quantum Otto cycle with single- and two spin-1/2 systems as its working medium. To mimic adiabatic dynamics at a finite time, we employ a shortcut-to-adiabaticity technique and evaluate the performance of the engine including the cost of the shortcut. We compare our results with the true adiabatic and nonadiabatic performances of the same cycle. Our findings indicate that the use of the shortcut-to-adiabaticity scheme significantly enhances the performance of the quantum Otto engine as compared to its adiabatic and nonadiabatic counterparts for different figures of merit.Publication Open Access Robust multipartite entanglement generation via a collision model(American Physical Society (APS), 2019) Campbell, Steve; Vacchini, Bassano; Paternostro, Mauro; Department of Physics; Müstecaplıoğlu, Özgür Esat; Çakmak, Barış; Faculty Member; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; 1674; 252838We examine a simple scheme to generate genuine multipartite entangled states across disjoint qubit registers. We employ a shuttle qubit that is sequentially coupled, in an energy preserving manner, to the constituents within each register through rounds of interactions. We establish that stable W-type entanglement can be generated among all qubits within the registers. Furthermore, we find that the entanglement is sensitive to how the shuttle is treated, showing that a significantly larger degree is achieved by performing projective measurements on it. Finally, we assess the resilience of this entanglement generation protocol to several types of noise and imperfections, showing that it is remarkably robust.Publication Open Access Quantum correlations and coherence in spin-1 Heisenberg chains(American Physical Society (APS), 2016) Malvezzi, A. L.; Karpat, G.; Fanchini, F. F.; Debarba, T.; Vianna, R. O.; Department of Physics; Çakmak, Barış; Department of Physics; College of SciencesWe explore quantum and classical correlations along with coherence in the ground states of spin-1 Heisenberg chains, namely the one-dimensional XXZ model and the one-dimensional bilinear biquadratic model, with the techniques of density matrix renormalization group theory. Exploiting the tools of quantum information theory, that is, by studying quantum discord, quantum mutual information, and three recently introduced coherence measures in the reduced density matrix of two nearest neighbor spins in the bulk, we investigate the quantum phase transitions and special symmetry points in these models. We point out the relative strengths and weaknesses of correlation and coherence measures as figures of merit to witness the quantum phase transitions and symmetry points in the considered spin-1 Heisenberg chains. In particular, we demonstrate that, as none of the studied measures can detect the infinite-order Kosterlitz-Thouless transition in the XXZ model, they appear to be able to signal the existence of the same type of transition in the biliear biquadratic model. However, we argue that what is actually detected by the measures here is the SU(3) symmetry point of the model rather than the infinite-order quantum phase transition. Moreover, we show in the XXZ model that examining even single site coherence can be sufficient to spotlight the second-order phase transition and the SU(2) symmetry point.Publication Open Access Collisional unfolding of quantum Darwinism(American Physical Society (APS), 2019) Campbell, Steve; Paternostro, Mauro; Vacchini, Bassano; Department of Physics; Müstecaplıoğlu, Özgür Esat; Çakmak, Barış; Faculty Member; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; 1674; 252838We examine the emergence of objectivity via quantum Darwinism through the use of a collision model, i.e., where the dynamics is modeled through sequences of unitary interactions between the system and the individual constituents of the environment, termed "ancillas." By exploiting versatility of this framework, we show that one can transition from a "Darwinistic" to an "encoding" environment by simply tuning their interaction. Furthermore, we establish that in order for a setting to exhibit quantum Darwinism we require a mutual decoherence to occur between the system and environmental ancillas, thus showing that system decoherence alone is not sufficient. Finally, we demonstrate that the observation of quantum Darwinism is sensitive to a nonuniform system-environment interaction.Publication Open Access Continuous dynamical decoupling and decoherence-free subspaces for qubits with tunable interaction(Springer, 2019) Yalçınkaya, İskender; Karpat, Göktuğ; Fanchini, F. F.; Department of Physics; Çakmak, Barış; Department of Physics; College of Sciences; 252838Protecting quantum states from the decohering effects of the environment is of great importance for the development of quantum computation devices and quantum simulators. Here, we introduce a continuous dynamical decoupling protocol that enables us to protect the entangling gate operation between two qubits from the environmental noise. We present a simple model that involves two qubits which interact with each other with a strength that depends on their mutual distance and generates the entanglement among them, as well as in contact with an environment. The nature of the environment, that is, whether it acts as an individual or common bath to the qubits, is also controlled by the effective distance of qubits. Our results indicate that the introduced continuous dynamical decoupling scheme works well in protecting the entangling operation. Furthermore, under certain circumstances, the dynamics of the qubits naturally led them into a decoherence-free subspace which can be used complimentary to the continuous dynamical decoupling.Publication Open Access Collectively enhanced thermalization via multiqubit collisions(American Physical Society (APS), 2019) Niedenzu, Wolfgang; Kurizki, Gershon; Department of Physics; Müstecaplıoğlu, Özgür Esat; Roman-Ancheyta, Ricardo; Çakmak, Barış; Manatuly, A.; Faculty Member; Researcher; Department of Physics; College of Sciences; Graduate School of Sciences and Engineering; 1674; N/A; 252838; N/AWe investigate the evolution of a target qubit caused by its multiple random collisions with N-qubit clusters. Depending on the cluster state, the evolution of the target qubit may correspond to its effective interaction with a thermal bath, a coherent (laser) drive, or a squeezed bath. In cases where the target qubit relaxes to a thermal state, its dynamics can exhibit a quantum advantage, whereby the target-qubit temperature can be scaled up proportionally to N-2 and the thermalization time can be shortened by a similar factor, provided the appropriate coherence in the cluster is prepared by nonthermal means. We dub these effects quantum superthermalization because of the analogies to superradiance. Experimental realizations of these effects are suggested.Publication Open Access Non-Markovianity, coherence, and system-environment correlations in a long-range collision model(American Physical Society (APS), 2017) Pezzutto, M.; Paternostro, M.; Department of Physics; Müstecaplıoğlu, Özgür Esat; Çakmak, Barış; Faculty Member; Department of Physics; College of Sciences; 1674; N/AWe consider the dynamics of a collisional model in which both the system and environment are embodied by spin-1/2 particles. In order to include non-Markovian features in our model, we introduce interactions among the environmental qubits and investigate the effect that different models of such interaction have on the degree of non-Markovianity of the system's dynamics. By extending that interaction beyond the nearest neighbor, we enhance the degree of non-Markovianity in the system's dynamics. A further significant increase can be observed if a collective interaction with the forthcoming environmental qubits is considered. However, the observed degree of non-Markovianity in this case is nonmonotonic with the increasing number of qubits included in the interaction. Moreover, one can establish a connection between the degree of non-Markovianity in the evolution of the system and the fading behavior of quantum coherence in its state as the number of collisions grows. We complement our study with an investigation of system-environment correlations and present an example of their importance on a physical upper bound on the trace distance derivative.