Browsing by Subject "Quantum information"

Now showing 1 - 5 of 5

Open Access
Entanglement, local measurements and symmetry
(Institute of Physics Publishing, 2003) Klyachko, A. A.; Shumovsky, A. S.
AbstractAdefinition of entanglement in terms of local measurements is discussed.Namely, the maximum entanglement corresponds to the states that cause thehighest level of quantum fluctuations in all local measurements determinedby the dynamic symmetry group of the system. A number of examplesillustrating this definition is considered
Open Access
Maximum entanglement and its proper measure
(Institute of Physics, 2004) Klyachko, A. A.; Shumovsky, A. S.
We discuss a definition of maximally entangled states in terms of maximum uncertainty of corresponding measurements. We describe a method of construction of bases of maximally entangled states. The entangled states that can be obtained from the maximally entangled states by means of SLOCC (stochastic local operations assisted by classical communications) we consider as semistable vectors. We discuss a measure of entanglement expressed in terms of a geometric invariant.
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
Study of junction and bias parameters in readout of phase qubits
(2012) Zandi H.; Safaei, S.; Khorasani, S.; Fardmanesh, M.
The exact numerical solution of the nonlinear Ginzburg-Landau equation for Josephson junctions is obtained, from which the precise nontrivial current density and effective potential of the Josephson junctions are found. Based on the resulting potential well, the tunneling probabilities of the associated bound states are computed which are in complete agreement with the reported experimental data. The effects of junction and bias parameters such as thickness of the insulating barrier, cross sectional area, bias current, and magnetic field are fully investigated using a successive perturbation approach. We define and compute figures of merit for achieving optimal operation of phase qubits and measurements of the corresponding states. Particularly, it is found that Josephson junctions with thicker barriers yield better performance in measurements of phase qubits. The variations of characteristic parameters such as life time of the states due to the above considered parameters are also studied and discussed to obtain the appropriate configuration setup.
Open Access
Topological methods for studying contextuality: N-Cycle scenarios and beyond
(MDPI AG, 2023-07-27) Kharoof, Aziz; İpek, Selman; Okay, Cihan
Simplicial distributions are combinatorial models describing distributions on spaces of measurements and outcomes that generalize nonsignaling distributions on contextuality scenarios. This paper studies simplicial distributions on two-dimensional measurement spaces by introducing new topological methods. Two key ingredients are a geometric interpretation of Fourier–Motzkin elimination and a technique based on the collapsing of measurement spaces. Using the first one, we provide a new proof of Fine’s theorem characterizing noncontextual distributions in N-cycle scenarios. Our approach goes beyond these scenarios and can describe noncontextual distributions in scenarios obtained by gluing cycle scenarios of various sizes. The second technique is used for detecting contextual vertices and deriving new Bell inequalities. Combined with these methods, we explore a monoid structure on simplicial distributions.