Macrorealism inequality for optoelectromechanical systems

Lambert, Neill; Johansson, Robert; Nori, Franco

doi:10.1103/physrevb.84.245421

Cited by 49 publications

(47 citation statements)

References 41 publications

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“…Our method as applied to the single spin case [4,6] (results not shown here) demonstrates that MLGI is not enhanced, rather it is suppressed, when a nonequilibrium temperature gradient is applied. Therefore, a two-qubit system is the smallest spin chain where nonequilibrium enhancement of LGI violations can be observed.…”

Section: Resultsmentioning

confidence: 99%

“…An emerging Leggett-Garg inequality (LGI) violation would mark a borderline between the classical and quantum worlds. Of special interest has been the guide provided by LGI for testing macroscopic realism in condensed matter systems [6][7][8][9][10][11][12] as well as in quantum optics setups [13,14] where focus has been put on LGI violations for open quantum systems in contact with realistic reservoirs.…”

Section: Introductionmentioning

confidence: 99%

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Enhanced violation of a Leggett-Garg inequality under nonequilibrium thermal conditions

2013

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We investigate both analytically and numerically violations of a Leggett-Garg inequality (LGI) for a composite quantum system in contact with two separate reservoirs at different temperatures. Remarkably we find that LGI violations can be enhanced when a heat current is established at low temperatures in a steady-state regime. Based on a Kraus operator decomposition of the non-unitary evolution for a system formed by two interacting spins or quantum bits, we provide analytical support for power law relations between dissipation strength and mean temperature in the borderlines separating parameter regions where non-equilibrium conditions affect differently the maximal LGI violation. Furthermore, a correspondence between spatial and temporal correlation inequalities is shown to persist even in such nonequilibrium thermal settings.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Enhanced violation of a Leggett-Garg inequality under nonequilibrium thermal conditions

2013

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“…It has been proven rigorously that for measurements given by just two projectors, Π + and Π − , onto eigenspaces associated with results Q = +1 and Q = −1, the maximum quantum value of K 3 is the same as for the qubit, irrespective of system size [9]. This has been reflected in several studies: the experiment of Ref.[16] on a three-level system obtained a maximum value less than 3 2 ; on the theory side, multi-level quantum systems such as a large spin [17], optoelectromechanical systems [18] and photosynthetic complexes [19] have also been observed to obey. From this, one might conclude that nothing new is to be gained from considering higher dimensional systems.…”

mentioning

confidence: 94%

“…[16] on a three-level system obtained a maximum value less than 3 2 ; on the theory side, multi-level quantum systems such as a large spin [17], optoelectromechanical systems [18] and photosynthetic complexes [19] have also been observed to obey…”

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confidence: 99%

Temporal Quantum Correlations and Leggett-Garg Inequalities in Multilevel Systems

2014

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We show that the quantum bound for temporal correlations in a Leggett-Garg test, analogous to the Tsirelson bound for spatial correlations in a Bell test, strongly depends on the number of levels N that can be accessed by the measurement apparatus via projective measurements. We provide exact bounds for small N , that exceed the known bound for the Leggett-Garg inequality, and show that in the limit N → ∞ the Leggett-Garg inequality can be violated up to its algebraic maximum.PACS numbers: 03.65. Ud, 03.65.Ta Introduction.-Bell inequalities place fundamental bounds on the nature of correlations between spatiallyseparated entities within a local hidden variable framework [1]. Leggett and Garg showed that temporal correlations obey similar inequalities based on assumptions of macroscopic realism and non-invasive measureability [2]. Quantum particles are bound neither by local hidden variables nor macroscopic realism and so can violate both Bell and Leggett-Garg inequalities (LGIs).The maximum degree to which a quantum system can violate a Bell inequality is known as the Tsirelson bound [3], significantly less than the largest-conceivable value, the algebraic bound [4]. Violations of a Bell inequality beyond the Tsirelson bound would be evidence of a new physics beyond quantum theory [6].With interest in the LGIs growing (see Ref.[7] for a review), we ask here whether there is such a thing as a temporal Tsirelson bound for the LGIs. In the light of some recent results [8,9] and given the formal symmetry between the two types of inequality [10,11] and the general trend towards unification between temporal and spatial correlations [12][13][14][15], one would expect that the Tsirelson bound for the LGIs holds analogously to the spatial case. Surprisingly, and as we show here, this is not the case. By considering a broader class of projective measurements than hitherto considered, we show that the maximum quantum violation of the LGIs can exceed the Tsirelson value, and increases with increasing system size, even up to the algebraic bound in the asymptotic limit.Let us now be more concrete and consider the simplest LGI which, for dichotomous observable Q = ±1, readswhere C βα = Q(t β )Q(t α ) is the correlation function of variable Q at the two times t β ≥ t α . For a two-level system, the maximum quantum value of K 3 is K max 3 = 3 2 [2], which we shall refer to as the Lüders bound, K Lüders 3 = 3 2 , for reasons to become clear shortly. It has been proven rigorously that for measurements given by just two projectors, Π + and Π − , onto eigenspaces associated with results Q = +1 and Q = −1, the maximum quantum value of K 3 is the same as for the qubit, irrespective of system size [9]. This has been reflected in several studies: the experiment of Ref.[16] on a three-level system obtained a maximum value less than 3 2 ; on the theory side, multi-level quantum systems such as a large spin [17], optoelectromechanical systems [18] and photosynthetic complexes [19] have also been observed to obey. From this, one might co...

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“…A hybrid architecture composed of optical modes and mechanical modes can thus be fruitfully utilized to design a quantum communication and quantum information processing unit which can store and transfer information coherently. Theoretical studies related to two mode system have been performed much in detail [17][18][19][20] .…”

Section: Introductionmentioning

confidence: 99%

Quantum dynamics of two-optical modes and a single mechanical mode optomechanical system: Selective energy exchange

Aggarwal

Bhattacherjee

2014

Optics Communications

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We study the quantum dynamics of an optomechanical setup comprising two optical modes and one mechanical mode. We show that the same system can undergo a Dicke-Hepp-Lieb superradiant type phase transition. We found that the coupling between the momentum quadratures of the two optical fields give rise to a new critical point. We show that selective energy exchange between any two modes is possible by coherent control of the coupling parameters. In addition we also demonstrate the occurrence of Normal Mode Splitting (NMS) in the mechanical displacement spectrum.

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Macrorealism inequality for optoelectromechanical systems

Cited by 49 publications

References 41 publications

Enhanced violation of a Leggett-Garg inequality under nonequilibrium thermal conditions

Enhanced violation of a Leggett-Garg inequality under nonequilibrium thermal conditions

Temporal Quantum Correlations and Leggett-Garg Inequalities in Multilevel Systems

Quantum dynamics of two-optical modes and a single mechanical mode optomechanical system: Selective energy exchange

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