Sudden change of local quantum uncertainty and geometry for arbitrary two-qubit X-states

2020 ◽  
Vol 19 (9) ◽  
Author(s):  
You-neng Guo ◽  
Hu-ping Peng ◽  
Ke Zeng ◽  
Guo-you Wang
Keyword(s):  
Sudden Change ◽  
Quantum Uncertainty ◽  
Local Quantum Uncertainty ◽  
Local Quantum

scholarly journals Invariant entanglement and generation of quantum correlations under global dephasing

2018 ◽  
Vol 96 (7) ◽  
pp. 705-710 ◽  
Author(s):  
Göktuğ Karpat
Keyword(s):  
Quantum Entanglement ◽  
Dynamical Behavior ◽  
Sudden Change ◽  
Geometric Approach ◽  
Quantum Correlations ◽  
Systematic Analysis ◽  
Quantum Uncertainty ◽  
Local Quantum Uncertainty ◽  
Local Quantum ◽  
Time Invariant

We investigate the dynamics of quantum entanglement and more general quantum correlations quantified via negativity and local quantum uncertainty, respectively, for two-qubit systems undergoing Markovian collective dephasing. Focusing on a two-parameter family of initial two-qubit density matrices, we study the relation of the emergence of the curious phenomenon of time-invariant entanglement and the dynamical behavior of local quantum uncertainty. Developing an illustrative geometric approach, we demonstrate the existence of distinct regions of quantum entanglement for the considered initial states and identify the region that allows for completely frozen entanglement throughout the dynamics, accompanied by generation of local quantum uncertainty. Furthermore, we present a systematic analysis of different dynamical behaviors of local quantum uncertainty, such as its sudden change or smooth amplification, in relation with the dynamics of entanglement.

Local quantum uncertainty versus negativity through Gisin states

2021 ◽  
pp. 2150023
Author(s):  
A. Sbiri ◽  
M. Mansour ◽  
Y. Oulouda
Keyword(s):  
Sudden Change ◽  
Quantum Correlations ◽  
Mixed States ◽  
Quantum Uncertainty ◽  
Local Quantum Uncertainty ◽  
Mixing Parameter ◽  
Local Quantum ◽  
Local Uncertainty ◽  
Bona Fide ◽  
Spin Coherent States

We investigate the pairwise quantum correlations in standard Gisin states and in Gisin states based on bipartite spin-coherent states by employing quantum negativity and quantum local uncertainty as bona fide quantum correlations measures. Gisin states are defined as mixtures of separable mixed states and some pure entangled ones. We compare the behavior of the two quantifiers of Gisin states and we find that both measures exhibit a sudden change in terms of the mixing parameter. Furthermore, we show that entangled Gisin states contain nonclassical correlations that are captured by the local quantum uncertainty and cannot be revealed by the negativity quantifier.

scholarly journals Local quantum uncertainty as a robust metric to characterize discord-like quantum correlations in subsets of the chromophores in photosynthetic light-harvesting complexes

2020 ◽  
Vol 66 (4 Jul-Aug) ◽  
pp. 525
Author(s):  
M. Chávez-Huerta ◽  
F. Rojas
Keyword(s):  
Quantum Coherence ◽  
Light Harvesting ◽  
Green Sulfur Bacteria ◽  
Quantum Correlations ◽  
Light Harvesting Complexes ◽  
Thermal Equilibrium State ◽  
Light Harvesting Complex ◽  
Quantum Uncertainty ◽  
Local Quantum Uncertainty ◽  
Local Quantum

Green sulfur bacteria is a photosynthetic organism whose light-harvesting complex accommodates a pigment-protein complex called Fenna-Matthews-Olson (FMO). The FMO complex sustains quantum coherence and quantum correlations between the electronic states of spatially separated pigment molecules as energy moves with nearly a 100% quantum efficiency to the reaction center. We present a method based on the quantum uncertainty associated to local measurements to quantify discord-like quantum correlations between two subsystems where one is a qubit and the other is a qudit. We implement the method by calculating local quantum uncertainty (LQU), concurrence, and coherence between subsystems of pure and mixed states represented by the eigenstates and by the thermal equilibrium state determined by the FMO Hamiltonian. Three partitions of the seven chromophores network define the subsystems: one chromophore with six chromophores, pairs of chromophores, and one chromophore with two chromophores. Implementation of the LQU approach allows us to characterize quantum correlations that had not been studied before, identify the most quantum correlated subsets of chromophores, and determine that, in the strongest associations of chromophores, the LQU is a monotonically increasing function of the coherence.

Local quantum uncertainty and trace distance discord dynamics for two-qubit X states embedded in non-Markovian environment

2018 ◽  
Vol 32 (20) ◽  
pp. 1850218 ◽  
Author(s):  
Youssef Khedif ◽  
Mohammed Daoud
Keyword(s):  
Quantum Correlations ◽  
Trace Distance ◽  
Markovian Environment ◽  
Quantum Uncertainty ◽  
Local Quantum Uncertainty ◽  
Local Quantum ◽  
Limiting Case ◽  
Analytical Expressions ◽  
Qubit States ◽  
Markovian Regime

We investigate the behavior of quantum correlations in some specific Werner-like two-qubit states, where the qubit interacts individually with non-Markovian environment. We employ the local quantum uncertainty and trace distance discord to quantify the amount of quantum correlations between the evolved qubits and the corresponding analytical expressions are derived. For specific values of the parameters characterizing the whole system, the dynamics of quantum correlations exhibits collapse and revival phenomena. The influence of the non-Markovianity is also investigated to analyze the monotonic decay of quantum correlations in the limiting case of Markovian regime. Furthermore, we show that trace distance discord captures quantum correlations that cannot be revealed by local quantum uncertainty in some particular situations.

Measuring non-Markovianity based on local quantum uncertainty

2014 ◽  
Vol 90 (4) ◽  
Author(s):  
Zhi He ◽  
Chunmei Yao ◽  
Qiong Wang ◽  
Jian Zou
Keyword(s):  
Quantum Uncertainty ◽  
Local Quantum Uncertainty ◽  
Local Quantum

The accelerated Gisin state: its non-locality, quantum correlations and efficiency to perform quantum masking

2021 ◽  
Vol 21 (15&16) ◽  
pp. 1274-1295
Author(s):  
A.G. Abdelwahab ◽  
A. Ghwail ◽  
N. Metwally ◽  
M.H. Mahran ◽  
A. -S. F. Obada
Keyword(s):  
Quantum Correlations ◽  
Local Behavior ◽  
Quantum Uncertainty ◽  
Acceleration Parameter ◽  
Masking Condition ◽  
Local Quantum Uncertainty ◽  
Local Quantum ◽  
Non Local ◽  
Classical Correlations ◽  
Non Locality

The local and non local behavior of the accelerated Gisin state are investigated either before or after filtering process. It is shown that, the possibility of predicting the non-local behavior is forseen at large values of the weight of the Gisin and acceleration parameters. Due to the filtering process, the non-locality behavior of the Gisin state is predicted at small values of the weight parameter. The amount of non classical correlations are quantified by means of the local quantum uncertainty (LQU)and the concurrence, where the LQU is more sensitive to the non-locality than the concurrence. The phenomenon of the sudden changes is displayed for both quantifiers. Our results show that, the accelerated Gisin state could be used to mask information, where all the possible partitions of the masked state satisfy the masking criteria. Moreover, there is a set of states, which satisfy the masking condition, that is generated between each qubit and its masker qubit. For this set, the amount of the non-classical correlations increases as the acceleration parameter increases . Further, the filtering process improves these correlations, where their maximum bounds are much larger than those depicted for non-filtered states.

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