Quantum correlations in composite systems

Sperling, Jan; Agudelo, Elizabeth; Vogel, W.

doi:10.1088/1361-6455/aa7438

Cited by 17 publications

(29 citation statements)

References 88 publications

(168 reference statements)

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“…One also can see from Eq. (19), that the upper bound for the negativity volume for pure separable bipartite hybrid states is determined by the negativity volume of the bosonic state. And the lower bound is defined by the negativity volume of the qubit.…”

Section: Negativity Volume Of Hybrid Bipartite Qubit-bosonic Statesmentioning

confidence: 98%

“…It is clear from Eq. (19), that for any given pure hybrid qubit-bosonic state |Ψ , if its negativity volume V (|Ψ ) is larger than the NV V (ρ pp ), corresponding to the pure product states in Eq. (19), then, the pure hybrid state possesses nonclassical correlations, since, in that case, the only source of the extra values of the NV of the Wigner function, apart from the nonclassicality generated by the reduced bosonic state, can be quantum correlations, in particular entanglement between qubit and bosonic subsystems.…”

Section: Negativity Volume Of Hybrid Bipartite Qubit-bosonic Statesmentioning

confidence: 99%

“…17 This could imply that such observed negativity cannot uniquely be utilized in the characterization of the nonclassicality in the discrete domain. As shown in, 19 one needs also to distinguish between different kinds of nonclassicality originating in the DV or CV domain. As such one cannot rely on the negativity of the Wigner function defined for hybrid states for the characterization of their nonclassicality.…”

Section: Introductionmentioning

confidence: 99%

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Negativity volume of the generalized Wigner function as an entanglement witness for hybrid bipartite states

Arkhipov

Barasiński

Svozilík

2018

Sci Rep

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In a recent paper, Tilma, Everitt et al. derived a generalized Wigner function that can characterize both the discrete and continuous variable states, i.e., hybrid states. As such, one can expect that the negativity of the generalized Wigner function applied to the hybrid states can reveal their nonclassicality, in analogy with the well-known Wigner function defined for the continuous variable states. In this work, we demonstrate that, indeed, the negativity volume of the generalized Wigner function of the hybrid bipartite states can be used as an entanglement witness for such states, provided that it exceeds a certain critical value. In particular, we study hybrid bipartite qubit–bosonic states and provide a qubit–Schrödinger cat state as an example. Since the detection of the generalized Wigner function of hybrid bipartite states in phase space can be experimentally simpler than the tomographic reconstruction of the corresponding density matrix, our results, therefore, present a convenient tool in the entanglement identification of such states.

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Section: Negativity Volume Of Hybrid Bipartite Qubit-bosonic Statesmentioning

confidence: 98%

Section: Negativity Volume Of Hybrid Bipartite Qubit-bosonic Statesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Negativity volume of the generalized Wigner function as an entanglement witness for hybrid bipartite states

Arkhipov

Barasiński

Svozilík

2018

Sci Rep

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“…Quantifying different types of correlations in quantum systems is a key area of research that has received a great deal of attention [62][63][64][65][66][67][68][69]. In parallel, phase-space methods have been utilized as a tool to identify and categorize quantum correlations [41,[70][71][72][73]. Further, these methods have been used to generate measures based on the emergence of negative quasi-probabilities in the Wigner function [37,[74][75][76].…”

Section: Visualizing Correlations In Hybrid Quantum Systemsmentioning

confidence: 99%

“…The technique presented here is based on this approach, however in [38], reduced Wigner functions are used and an envelope is further applied, potentially losing many of the non-local correlations that arise due to entanglement. Other methods for combining CV Wigner function tomography with other representations of DV systems have been created [39][40][41], however, only the CV system was treated using the Wigner function formulation. The visualization technique used in [38] displays heterogeneous degrees of freedom, highlighting the power of a hybrid Wigner function approach for visualizing correlations.…”

mentioning

confidence: 99%

Visualization of correlations in hybrid discrete—continuous variable quantum systems

et al. 2020

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In this work we construct Wigner functions for hybrid continuous and discrete variable quantum systems. We demonstrate new capabilities in the visualization of the interactions and correlations between discrete and continuous variable quantum systems, where visualizing the full phase space has proven difficult in the past due to the high number of degrees of freedom. Specifically, we show how to clearly distinguish signatures that arise due to quantum and classical correlations in an entangled Bellcat state. We further show how correlations are manifested in different types of interaction, leading to a deeper understanding of how quantum information is shared between two subsystems. Understanding the nature of the correlations between systems is central to harnessing quantum effects for information processing; the methods presented here reveal the nature of these correlations, allowing a clear visualization of the quantum information present in these hybrid discrete-continuous variable quantum systems. The methods presented here could be viewed as a form of quantum state spectroscopy.Bloch sphere [20][21][22][23][24][25][26]. For example, there have been various proposals put forward that use a continuous Wigner function to reveal correlations between DV systems [26][27][28]. These methods have further been validated through the direct measurement of phase-space to reveal quantum correlations [28][29][30][31]. Recently this has been extended to experiments validating atomic Schrödinger cat states of up to 20 superconducting qubits [32].A case that has not been explored in much detail is the phase-space representation of CV-DV hybridization. This hybridisation is seen in many applications of quantum technologies, including simple gate models for quantum computers, such as hybrid two-qubit gates [33,34], and CV microwave pulse control of DV qubits [35]. The generation of hybrid quantum correlations within CV-DV hybrid 5 systems commonly takes place within the framework of cavity quantum electrodynamics, that describes the interaction between a two-level quantum system and a single mode of a microwave field. These models can be further used to describe the effect of circuit quantum electrodynamics, and to consider the interaction of the microwave field with an artificial atom. Analyzing these interactions within the framework of the Jaynes-Cummings model [36] allows us to display how quantum information is shared between the CV and DV systems.A number of papers [23, 24, 37] have shown the mathematical construction of hybrid states within the phase space, these have been constructed without giving a way to visually display the degrees of freedom of such composite systems. A method for displaying states with heterogeneous degrees of freedom, using the Wigner function, came from the application of composite phase-space methods to quantum chemistry [38]. The technique presented here is based on this approach, however in [38], reduced Wigner functions are used and an envelope is further applied, potentially losing many o...

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Generalized Quantum Correlations in Discrete Variable Systems

Shähandeh

2019

Springer Theses

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Quantum correlations in composite systems

Cited by 17 publications

References 88 publications

Negativity volume of the generalized Wigner function as an entanglement witness for hybrid bipartite states

Negativity volume of the generalized Wigner function as an entanglement witness for hybrid bipartite states

Visualization of correlations in hybrid discrete—continuous variable quantum systems

Generalized Quantum Correlations in Discrete Variable Systems

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