Converting multilevel nonclassicality into genuine multipartite entanglement

Regula, Bartosz; Piani, Marco; Cianciaruso, Marco; Bromley, Thomas R.; Streltsov, Alexander; Adesso, Gerardo

doi:10.1088/1367-2630/aaae9d

Cited by 41 publications

(57 citation statements)

References 69 publications

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“…As an aside, the plot for the current once again illustrates the phenomenon of current inversion. The other parameters are the same as those in figure 2. the amount of coherence at the input, akin to the analysis in [70]. In the second case, 'charging' of the initially thermal rotor is possible only if the tunneling rate is sufficiently high.…”

Section: Discussionmentioning

confidence: 99%

Quantum current in dissipative systems

Hovhannisyan

Imparato

2019

New J. Phys.

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Describing current in open quantum systems can be problematic due to the subtle interplay of quantum coherence and environmental noise. Probing the noise-induced current can be detrimental to the tunneling-induced current and vice versa. We derive a general theory for the probability current in quantum systems arbitrarily interacting with their environment that overcomes this difficulty. We show that the current can be experimentally measured by performing a sequence of weak and standard quantum measurements. We exemplify our theory by analyzing a simple Smoluchowski-Feynmantype ratchet consisting of two particles, operating deep in the quantum regime. Fully incorporating both thermal and quantum effects, the current generated in the model can be used to detect the onset of 'genuine quantumness' in the form of quantum contextuality. The model can also be used to generate steady-state entanglement in the presence of arbitrarily hot environment.

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Section: Discussionmentioning

confidence: 99%

Quantum current in dissipative systems

Hovhannisyan

Imparato

2019

New J. Phys.

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“…This extension has found several applications in remote quantum protocols, including the tasks of quantum state merging [42,43] and assisted coherence distillation [38,41], which has also been demonstrated experimentally very recently [44]. Coherence in multipartite systems has also been studied with respect to other types of nonclassicality such as entanglement [21,23,30,45] and quantum discord [46,47].…”

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confidence: 91%

“…Further approaches, also going beyond incoherent states, have been investigated recently in Refs. [18][19][20][21][22][23].The quantification of coherence is another important research direction. Postulates for coherence quantifiers have been presented [5,6,8,24], based on earlier approaches in entanglement theory [3,4,25].…”

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confidence: 99%

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Structure of the Resource Theory of Quantum Coherence

et al. 2017

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Quantum coherence is an essential feature of quantum mechanics which is responsible for the departure between classical and quantum world. The recently established resource theory of quantum coherence studies possible quantum technological applications of quantum coherence, and limitations which arise if one is lacking the ability to establish superpositions. An important open problem in this context is a simple characterization for incoherent operations, constituted by all possible transformations allowed within the resource theory of coherence. In this work, we contribute to such a characterization by proving several upper bounds on the maximum number of incoherent Kraus operators in a general incoherent operation. For a single qubit, we show that the number of incoherent Kraus operators is not more than 5, and it remains an open question if this number can be reduced to 4. The presented results are also relevant for quantum thermodynamics, as we demonstrate by introducing the class of Gibbs-preserving strictly incoherent operations, and solving the corresponding mixedstate conversion problem for a single qubit.Quantum resource theories [1, 2] provide a strong framework for studying fundamental properties of quantum systems and their applications for quantum technology. The basis of any quantum resource theory is the definition of free states and free operations. Free states are quantum states which can be prepared at no additional cost, while free operations capture those physical transformations which can be implemented without consumption of resources. Having identified these two main features, one can study the basic properties of the corresponding theory, such as possibility of state conversion, resource distillation, and quantification. An important example is the resource theory of entanglement, where free states are separable states, and free operations are local operations and classical communication [3,4].In the resource theory of quantum coherence [5-9], free states are identified as incoherent statesi.e., states which are diagonal in a fixed specified basis {|i }. The choice of this basis depends on the particular problem under study, and in many relevant scenarios such a basis is naturally singled out by the unavoidable decoherence [10]. The definition of free operations within the theory of coherence is not unique, and several approaches have been discussed in the literature, based on different physical (or mathematical) considerations [8]. Two important frameworks are known as incoherent [6] and strictly incoherent operations [7,11], which will be denoted by IO and SIO, respectively. The characterizing feature of IO is the fact that they admit an incoherent Kraus decomposition, i.e., they can be written as [6] where each of the Kraus operators K j cannot create coherence individually, K j |m ∼ |n for suitable integers n and m. This approach is motivated by the fact that any quantum operation can be interpreted as a selective measurement in which outcome j occurs with probability p j = Tr[K j ρK ...

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“…Some known measures include geometric measures [2], the robustness of coherence [6][7][8], and entanglement based measures [9]. Coherence measures have now been studied in relation to a diverse range of quantum effects such as quantum interference [10], exponential speed-up in quantum algorithms [11,12] and quantum metrology [13,14], nonclassical light [15][16][17], quantum macroscopicity [18,19] and quantum correlations [20][21][22][23][24][25]. An overview of coherence measures and their structure may be found in [26,27].…”

Section: Introductionmentioning

confidence: 99%

Optimizing nontrivial quantum observables using coherence

2019

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In this paper we consider the quantum resources required to maximize the mean values of any nontrivial quantum observable. We show that the task of maximizing the mean value of an observable is equivalent to maximizing some form of coherence, up to the application of an incoherent operation. For any nontrivial observable, there always exists a set of preferred basis states where the superposition between such states is always useful for optimizing the mean value of a quantum observable. The usefulness of such states is expressed in terms of an infinitely large family of valid coherence measures which is then shown to be efficiently computable via a semidefinite program. We also show that these coherence measures respect a hierarchy that gives the robustness of coherence and the l 1 norm of coherence additional operational significance in terms of such optimization tasks.

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Converting multilevel nonclassicality into genuine multipartite entanglement

Cited by 41 publications

References 69 publications

Quantum current in dissipative systems

Quantum current in dissipative systems

Structure of the Resource Theory of Quantum Coherence

Optimizing nontrivial quantum observables using coherence

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