Browsing by Subject "Quantum entanglement"

Now showing 1 - 9 of 9

Open Access
Entanglement in local systems
(2008) Binicioğlu Çetiner, Sinem
In this study, we first discuss entanglement measures and we introduce a way to construct generic entangled states of an n-level quantum system. Then we discuss entanglement as a local object. Particularly we use a spin qutrit, and investigate whether an entangled spin qutrit obeys entanglement criteria or not. While doing this, we also discuss, which criteria of entanglement are essential and which of them are not. We show the relation between quantum fluctuations and entanglement. Lastly, we discuss Bell type inequalities and we show violation of a Bell type condition by a single particle entangled state.
Open Access
General entanglement
(IOP, 2006) Klyachko, Alexander A.; Shumovsky, Alexander S.
The paper contains a brief review of an approach to quantum entanglement based on analysis of dynamic symmetry of systems and quantum uncertainties, accompanying the measurement of mean value of certain basic observables. The latter are defined in terms of the orthogonal basis of Lie algebra, corresponding to the dynamic symmetry group. We discuss the relativity of entanglement with respect to the choice of basic observables and a way of stabilization of robust entanglement in physical systems.
Open Access
Nonthermal Quantum Channels as a Thermodynamical Resource
(American Physical Society, 2015) Navascués, M.; García-Pintos L.P.
Quantum thermodynamics can be understood as a resource theory, whereby thermal states are free and the only allowed operations are unitary transformations commuting with the total Hamiltonian of the system. Previous literature on the subject has just focused on transformations between different state resources, overlooking the fact that quantum operations which do not commute with the total energy also constitute a potentially valuable resource. In this Letter, given a number of nonthermal quantum channels, we study the problem of how to integrate them in a thermal engine so as to distill a maximum amount of work. We find that, in the limit of asymptotically many uses of each channel, the distillable work is an additive function of the considered channels, computable for both finite dimensional quantum operations and bosonic channels. We apply our results to bound the amount of distillable work due to the natural nonthermal processes postulated in the Ghirardi-Rimini-Weber (GRW) collapse model. We find that, although GRW theory predicts the possibility of extracting work from the vacuum at no cost, the power which a collapse engine could, in principle, generate is extremely low. © 2015 American Physical Society. © 2015 American Physical Society.
Open Access
Quantifying quantum information via uncertainties
(OSA, 2007) Öztop, Barış; Klyachko, Alexander A.; Shumovsky, Alexander S.
We show, for a state ψ of a quantum system with the dynamic symmetry given by the Lie group G, total amount of quantum information and entanglement is provided by summarized uncertainty of basic observables.
Open Access
Quantum correlations among superradiant bose-einstein condensate atoms
(M A I K Nauka - Interperiodica, 2010) Taşgin, M. E.; Öztop, B.; Oktel, M. Ö.; Müstecapliog̃lu, Ö. E.
Quantum correlations among atoms in superradiant Bose-Einstein condensates are discussed. It is shown that atoms in the superradiant atomic condensate can exhibit continuous variable quantum entanglement analogous to Einstein-Podolsky-Rosen (EPR)-type quantum correlations. Comparison to quantum entanglement in the Dicke model in thermal equilibrium is provided.
Open Access
Quantum entaglement and order parameter in a paired finite Fermi system
(Elsevier Science, 2002-12) Gedik, Z.
We study the pairing correlations in a finite Fermi system from the quantum entanglement point of view. We investigate the relation between the order parameter, which has been introduced recently to describe both finite and infinite superconductors, and the concurrence. For a proper definition of the concurrence, we argue that a possible generalization of the spin flip transformation is a time reversal operation. While for a system with indefinite number of particles concurrence is a good measure of entanglement, for a finite system it does not distinguish between normal and superconducting states. We propose that the expectation value of the radial operator for the total pseudospin can be used to identify entanglement of pairing.
Open Access
Quantum entanglement of spin-1 bosons with coupled ground states in optical lattices
(IOP Institute of Physics Publishing, 2009) Öztop, B.; Oktel, M. Ö.; Müstecapliolu, Ö. E.; You, L.
We examine particle entanglement, characterized by pseudo-spin squeezing, of spin-1 bosonic atoms with coupled ground states in a one-dimensional optical lattice. Both the superfluid and Mott-insulator phases are investigated separately for ferromagnetic and antiferromagnetic interactions. Mode entanglement is also discussed in the Mott-insulating phase. The role of a small but nonzero angle between the polarization vectors of counter-propagating lasers forming the optical lattice on quantum correlations is investigated as well.
Open Access
Quantum entanglement via superradiance of a Bose-Einstein condensate
(Institute of Physics Publishing, 2010) Taşgın, M. E.; Oktel, M. Ö.; You, L.; Müstecaploǧlu, Ö. E.
We adopt the coherence and built-in swap mechanism in sequential superradiance as a tool for obtaining continuous-variable (electric/magnetic fields) quantum entanglement of two counter-propagating pulses emitted from the two end-fire modes. In the first-sequence, end-fire modes are entangled with the side modes. In the second sequence, this entanglement is swapped to in between the two opposite end-fire modes. Additionally, we also examine the photon number correlations. No quantum correlations is observed in this variable.
Open Access
Tunable zero-index photonic crystal waveguide for two-qubit entanglement detection
(American Chemical Society, 2016) Özgün E.; Özbay, Ekmel; Caglayan, H.
Preparation and measurement of an entangled state are essential in quantum information applications. The recent theoretical works on preparing and measuring entangled states via coupled quantum dot-waveguide platforms are promising. However, an alternative strategy is still needed for more accessible implementations. In this Article, we propose a simple but powerful medium for quantum information processing and communication consisting of a zero-index photonic crystal (PC) waveguide (WG). By exploiting the zero-index behavior of the PC WG, we overcome the difficulty of sensitivity in quantum dots' location, which is one of the main challenges for preparing and measuring a two-qubit entangled state. Moreover, our platform possesses the feature of tunability, which allows it to operate in different wavelength regimes. The suggested medium is also promising for realizing long-range spatial coherence as well as long-range entanglement. © 2016 American Chemical Society.