scholarly journals Probing multipartite entanglement, coherence and quantum information preservation under classical Ornstein-Uhlenbeck noise

Author(s):  
Atta Ur Rahman ◽  
Muhammad Javed ◽  
Zhaoxu Ji ◽  
Arif Ullah

Abstract We address entanglement, coherence, and information protection in a system of four non-interacting qubits coupled with different classical environments, namely: common, bipartite, tripartite, and independent environments described by Ornstein-Uhlenbeck (ORU) noise. We show that quantum information preserved by the four qubit state is more dependent on the coherence than the entanglement using time-dependent entanglement witness, purity, and Shannon entropy. We find these two quantum phenomena directly interrelated and highly vulnerable in environments with ORU noise, resulting in the pure exponential decay of a considerable amount. The current Markovian dynamical map, as well as suppression of the fluctuating character of the environments, are observed to be entirely attributable to the Gaussian nature of the noise. The increasing number of environments are witnessed to speed up the amount of decay. Unlike other noises, the current noise parameter's flexible range is readily exploitable, ensuring long enough preserved memory properties. The four-qubit GHZ state, besides having a large information storage potential, stands partially entangled and coherent in common environments for an indefinite duration. In addition, we derive computational values for each system-environment interaction, which will help quantum practitioners to optimize the related classical environments.

Author(s):  
Alexey V. Kavokin ◽  
Jeremy J. Baumberg ◽  
Guillaume Malpuech ◽  
Fabrice P. Laussy

Microcavity polaritons have demonstrated their unique propensity to host macroscopic quantum phenomena. While they appear to be highly promising for applications in a classical realm, they are still far from competing even with decade old electronics. Another playground where polaritons could emerge as strong contenders is the microscopic quantum regime with single-particle effects and nonlinearities at the one-polariton level. Several theoretical proposals exist to explore polariton blockade mechanisms, realize sophisticated quantum phase transitions, implement quantum simulations and/or quantum information processing, thereby opening a new page of the polariton physics when such ideas will be implemented in the laboratory.


2018 ◽  
Vol 69 (12) ◽  
pp. 1237 ◽  
Author(s):  
G. C. Wright ◽  
M. G. Borgognone ◽  
D. J. O Connor ◽  
R. C. N. Rachaputi ◽  
R. J. Henry ◽  
...  

Breeding for improved blanchability—the propensity of the testa (skin) to be removed from the kernel following rapid heat treatment—is a priority for improvement in the Australian Peanut Breeding Program (APBP). Easy removal of the testa by blanching is required for processing of peanuts into peanut butter and various other confectionary products. Thus, blanchability is an economically important trait in any newly released cultivar in Australia. A better understanding of the range of genetic variation, nature of inheritance and genotype×environment (G×E) interactions, and the development of a low-cost method to phenotype in early generations, could speed up breeding for this trait. Studies were conducted to develop a low-cost, rapid method utilising minimal amounts of seed to phenotype in early generations, along with an assessment of G×E interactions over a range of years and environments to derive optimal selection protocols. Use of a smaller kernel sample size than standard (50 vs 200g) was effective for accurately assessing blanchability in breeding lines and could allow selection in early generations (e.g. in seed produced from a single F2 plant where seed supply is adequate). G×E interaction for blanchability was shown to be very low. Genotypic variance explained 62–100% of the total variance for blanchability, assessed in two diverse germplasm pools including 107 accessions in the USA mini-core over three environments and multiple APBP breeding lines grown over nine different years–environments. Genotypic correlations between all environments were very high (~0.60–0.96), with heritability for the blanchability trait estimated to be very high (0.74–0.97) across the 13 trials. The results clearly demonstrate that effective selection for improved blanchability can be conducted in early generations and in a limited number of contrasting environments to ensure consistency of results.


Author(s):  
Konstantin Antipin

Abstract Genuine entanglement is the strongest form of multipartite entanglement. Genuinely entangled pure states contain entanglement in every bipartition and as such can be regarded as a valuable resource in the protocols of quantum information processing. A recent direction of research is the construction of genuinely entangled subspaces — the class of subspaces consisting entirely of genuinely entangled pure states. In this paper we present methods of construction of such subspaces including those of maximal possible dimension. The approach is based on the composition of bipartite entangled subspaces and quantum channels of certain types. The examples include maximal subspaces for systems of three qubits, four qubits, three qutrits. We also provide lower bounds on two entanglement measures for mixed states, the concurrence and the convex-roof extended negativity, which are directly connected with the projection on genuinely entangled subspaces.


2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Árpád Kurkó ◽  
Peter Domokos ◽  
András Vukics ◽  
Thomas Bækkegaard ◽  
Nikolaj Thomas Zinner ◽  
...  

AbstractTrapped atomic ensembles are convenient systems for quantum information storage in the long-lived sublevels of the electronic ground state and its conversion to propagating optical photons via stimulated Raman processes. Here we investigate a phase-matched emission of photons from a coherently prepared atomic ensemble. We consider an ensemble of cold atoms in an elongated harmonic trap with normal density distribution, and determine the parameters of paraxial optics to match the mode geometry of the emitted radiation and optimally collect it into an optical waveguide.


Entropy ◽  
2020 ◽  
Vol 22 (7) ◽  
pp. 747
Author(s):  
Arkady Plotnitsky

Following the view of several leading quantum-information theorists, this paper argues that quantum phenomena, including those exhibiting quantum correlations (one of their most enigmatic features), and quantum mechanics may be best understood in quantum-informational terms. It also argues that this understanding is implicit already in the work of some among the founding figures of quantum mechanics, in particular W. Heisenberg and N. Bohr, half a century before quantum information theory emerged and confirmed, and gave a deeper meaning to, to their insights. These insights, I further argue, still help this understanding, which is the main reason for considering them here. My argument is grounded in a particular interpretation of quantum phenomena and quantum mechanics, in part arising from these insights as well. This interpretation is based on the concept of reality without realism, RWR (which places the reality considered beyond representation or even conception), introduced by this author previously, in turn, following Heisenberg and Bohr, and in response to quantum information theory.


2014 ◽  
Vol 21 (04) ◽  
pp. 1450008 ◽  
Author(s):  
Mazhar Ali

We study the dynamics of genuine multipartite entanglement under non-Markovian noise. Using a computable entanglement monotone for multipartite systems, we investigate a system of three qubits each of which is individually exposed to classical Ornstein–Uhlenbeck noise. We found that the W state mixed with the maximally mixed state is the most fragile state, whereas a similar mixture of GHZ state exhibits robust behaviour. We compare dynamics of these states with dynamics of similar mixtures of random states and weighted graph states. We also discuss the limiting cases.


2016 ◽  
Vol 94 (11) ◽  
pp. 1142-1147 ◽  
Author(s):  
Hong-Mei Zou ◽  
Mao-Fa Fang

Based on the entropic uncertainty relation in the presence of quantum memory, the entanglement witness of two atoms in dissipative cavities is investigated by using the time-convolutionless master-equation approach. We discuss in detail the influences of the non-Markovian effect and the atom–cavity coupling on the lower bound of the entropic uncertainty relation and entanglement witness. The results show that, with the coupling increasing, the number of the time zone witnessed will increase so that the entanglement can be repeatedly witnessed. Enhancing the non-Markovian effect can add the number of the time zone witnessed and lengthen the time of entanglement witness. The results can be applied in quantum measurement, entanglement detecting, quantum cryptography task, and quantum information processing.


2015 ◽  
Vol 13 (06) ◽  
pp. 1550044 ◽  
Author(s):  
P. Espoukeh ◽  
R. Rahimi ◽  
S. Salimi ◽  
P. Pedram

Many-qubit entanglement is crucial for quantum information processing although its exploitation is hindered by the detrimental effects of the environment surrounding the many-qubit system. It is thus of importance to study the dynamics of general multipartite non-classical correlation, including but not restricted to entanglement, under noise. We did this study for four-qubit Greenberger–Horne–Zeilinga (GHZ) state under most common noises in an experiment and found that non-classical correlation is more robust than entanglement except when it is imposed to dephasing channel. Quantum discord presents a sudden transition in its dynamics for Pauli-X and Pauli-Y noises as well as Bell-diagonal states interacting with dephasing reservoirs and it decays monotonically for Pauli-Z and isotropic noises.


2018 ◽  
Vol 16 (04) ◽  
pp. 1850037 ◽  
Author(s):  
Xiao-Yu Chen ◽  
Li-Zhen Jiang ◽  
Zhu-An Xu

A Multipartite entangled state has many different kinds of entanglements specified by the number of partitions. The most essential example of multipartite entanglement is the entanglement of multi-qubit Greenberger–Horne–Zeilinger (GHZ) state in white noise. We explicitly construct the entanglement witnesses for these states with stabilizer generators of the GHZ states. For an [Formula: see text] qubit GHZ state in white noise, we demonstrate the necessary and sufficient criterion of separability when it is divided into [Formula: see text] parties with [Formula: see text] for arbitrary [Formula: see text] and [Formula: see text]. The criterion covers more than a half of all kinds of partial entanglements for [Formula: see text]-qubit GHZ states in white noise. For the rest of multipartite entanglement problems, we present a method to obtain the sufficient conditions of separability. As an application, we consider [Formula: see text] qubit GHZ state as a codeword of the degenerate quantum code passing through depolarizing channel. We find that the output state is neither genuinely entangled nor fully separable when the quantum channel capacity reduces from positive to zero.


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