Towards quantum cybernetics

Girolami, Davide; Schmidt, Rebecca; Adesso, Gerardo

doi:10.1002/andp.201500133

Cited by 7 publications

(6 citation statements)

References 65 publications

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“…We hope that the present analysis can stimulate further research in order to pin down the relevance of non-Markovian dynamics in quantum information processing and in the description and simulation of complex quantum systems in the biological, physical, and social domains [59].…”

Section: Discussionmentioning

confidence: 92%

Characterizing non-Markovianity via quantum interferometric power

2015

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Non-Markovian evolution in open quantum systems is often characterized in terms of the backflow of information from environment to system and is thus an important facet in investigating the performance and robustness of quantum information protocols. In this work, we explore non-Markovianity through the breakdown of monotonicity of a metrological figure of merit, called the quantum interferometric power, which is based on the minimal quantum Fisher information obtained by local unitary evolution of one part of the system, and can be interpreted as a quantifier of quantum correlations beyond entanglement. We investigate our proposed non-Markovianity indicator in two relevant examples. First, we consider the action of a single-party dephasing channel on a maximally entangled two-qubit state, by applying the Jamiołkowski-Choi isomorphism. We observe that the proposed measure is consistent with established non-Markovianity quantifiers defined using other approaches based on dynamical divisibility, distinguishability, and breakdown of monotonicity for the quantum mutual information. Further, we consider the dynamics of two-qubit Werner states, under the action of a local, single-party amplitude damping channel, and observe that the nonmonotonic evolution of the quantum interferometric power is more robust than the corresponding one for entanglement in capturing the backflow of quantum information associated with the non-Markovian process. Implications for the role of non-Markovianity in quantum metrology and possible extensions to continuous variable systems are discussed.

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Section: Discussionmentioning

confidence: 92%

Characterizing non-Markovianity via quantum interferometric power

2015

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“…This intriguing connection between thermodynamic performance and quantum correlations beyond entanglement poses the question of whether or not the latter act conclusively as resources in simple cooling protocols, such as the one considered here, or, more generally, in measurement-based quantum feedback control tasks. This open question certainly deserves detailed examination: it is not only relevant for practical applications of control theory in the rapidly developing field of quantum technologies, but also, from a more fundamental perspective, it may help to further clarify the role of quantum effects in thermodynamics and, broadly speaking, in the regulation of complex phenomena [84].…”

Section: Discussionmentioning

confidence: 99%

Thermodynamics of Quantum Feedback Cooling

Liuzzo-Scorpo

Correa

Schmidt

et al. 2016

Entropy

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Abstract:The ability to initialize quantum registers in pure states lies at the core of many applications of quantum technologies, from sensing to quantum information processing and computation. In this paper, we tackle the problem of increasing the polarization bias of an ensemble of two-level register spins by means of joint coherent manipulations, involving a second ensemble of ancillary spins and energy dissipation into an external heat bath. We formulate this spin refrigeration protocol, akin to algorithmic cooling, in the general language of quantum feedback control, and identify the relevant thermodynamic variables involved. Our analysis is two-fold: on the one hand, we assess the optimality of the protocol by means of suitable figures of merit, accounting for both its work cost and effectiveness; on the other hand, we characterise the nature of correlations built up between the register and the ancilla. In particular, we observe that neither the amount of classical correlations nor the quantum entanglement seem to be key ingredients fuelling our spin refrigeration protocol. We report instead that a more general indicator of quantumness beyond entanglement, the so-called quantum discord, is closely related to the cooling performance.

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“…In this scenario energy fluctuations play an important rule, thermodynamic quantities as work and entropy production are defined by their mean values, and the laws of thermodynamics still hold on average. The thermodynamic description of quantum many-body systems is significant for understanding the limits of the emerging quantum technology [1][2][3][4][5][6] . Fluctuation theorems [7][8][9][10][11][12][13][14] have been key tools to describe the unavoidable fluctuations in the non-equilibrium dynamics and related experiments have been performed for small, non-interacting systems [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] , in both the classical and quantum domain.…”

Section: Introductionmentioning

confidence: 99%

DFT-inspired methods for quantum thermodynamics

Herrera

Serra

D’Amico

2017

Sci Rep

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In the framework of quantum thermodynamics, we propose a method to quantitatively describe thermodynamic quantities for out-of-equilibrium interacting many-body systems. The method is articulated in various approximation protocols which allow to achieve increasing levels of accuracy, it is relatively simple to implement even for medium and large number of interactive particles, and uses tools and concepts from density functional theory. We test the method on the driven Hubbard dimer at half filling, and compare exact and approximate results. We show that the proposed method reproduces the average quantum work to high accuracy: for a very large region of parameter space (which cuts across all dynamical regimes) estimates are within 10% of the exact results.

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Towards quantum cybernetics

Cited by 7 publications

References 65 publications

Characterizing non-Markovianity via quantum interferometric power

Characterizing non-Markovianity via quantum interferometric power

Thermodynamics of Quantum Feedback Cooling

DFT-inspired methods for quantum thermodynamics

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