Update(06.08.14): Below are the slides from Rosario’s talk. He presented many results and posed some nice questions. Thanks Rosario!

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As I mentioned in a previous post, the first week of August (04-08) there will many quantum-info guests here at qig@CBPF. We basically have a self organized small conference thing going on. Just to have some sort of structure, we asked Rosario to give a talk on his latest results about dynamics of quantum correlations. See the details below. If you are willing to experience the quantum-info gathering next week at CBPF, just pop up here!

Speaker: Rosario Lo Franco (University of Nottingham)

Title: On the theoretical and experimental dynamics of quantum correlation resources in independent environments

Coordinates: room 601D, CBPF. 06.08, 16:00h

Abstract: Quantum correlations (entanglement, discord, nonlocality) in composite quantum systems are essential resources for quantum information processing [1, 2]. The exploitation of these quantum resources is jeopardized by the detrimental effects of the environment surrounding the quantum system. For instance, under Markovian noise they decay asymptotically or disappear at a finite time [2–4]. This drawback leads one to look for conditions where quantum correlations can be recovered and preserved during the evolution. To this aim non-Markovian noise, arising from strong couplings or structured environments, has been shown to be fundamental because of its memory effects. Quantum correlations between qubits in independent non-Markovian environments can exhibit revivals [2, 5, 6] and also freezing under suitable conditions [5, 7, 8], giving extensions of their use. For composite quantum systems within independent quantum environments, revivals of quantum correlations are typically interpreted as due to correlation exchanges induced by the back-action on the systems by their non-Markovian quantum environments [9-12]. Recently, it has been shown that revivals of quantum correlations may also occur when the environment is classical, thus unable to store quantum correlations, and forbids system-environment back-action [13-19]. This fact leads to basic issues on the interpretation of this phenomenon, in particular about the role of: (i) classical environments in reviving quantum correlations; (ii) collective effects of the environment on the qubits; (iii) memory effects; (iv) possible system-environment correlations.

In this lecture I present an overview of some theoretical and experimental results about the dynamics of quantum correlations in independent environments, particularly under non-Markovian conditions. I then focus on the case of classical environments and describe a model suitable to address this issue [19]. I report the results of an all-optical experiment that simulates this model and allows us to observe and control revivals of quantum correlations without system-environment back-action [19]. Finally, I discuss about non-Markovianity and provide a possible interpretation showing the role of the classical environment in this phenomenon. The findings so far tell us that revivals of quantum correlations are a dynamical feature of composite open systems irrespective of the nature, classical or quantum, of the environment.

[1] R. Horodecki et al., Rev. Mod. Phys. 81, 865 (2009).

[2] K. Modi et al., Rev. Mod. Phys. 84, 1655 (2012).

[3] T. Yu and J. H. Eberly, Science 323, 598 (2009).

[4] J.-S. Xu et al., Nature Commun. 1, 7 (2010).

[5] R. Lo Franco et al., Int. J. Mod. Phys. B 27, 1345053 (2013).

[6] J.-S. Xu et al., Phys. Rev. Lett. 104, 100502 (2010).

[7] P. Haikka et al., Phys. Rev. A 87, 010103(R) (2013).

[8] B. Aaronson, R. Lo Franco, and G. Adesso, Phys. Rev. A 88, 012120 (2013).

[9] B.-H. Liu et al., Nature Phys. 7, 931 (2011).

[10] B. Bellomo, R. Lo Franco, and G. Compagno, Phys. Rev. Lett. 99, 160502 (2007).

[11] C. E. Lopez, G. Romero, J. C. Retamal, Phys. Rev. A 81, 062114 (2010).

[12] A. Chiuri et al., Sci. Rep. 2, 968 (2012).

[13] R. Lo Franco et al., Phys. Scr. T147, 014019 (2012).

[14] C. Benedetti et al. Phys. Rev. A 87, 052328 (2013).

[15] A. D’Arrigo, R. Lo Franco, G. Benenti, E. Paladino, and G. Falci, Phys. Scr. T153, 014014 (2013).

[16] B. Aaronson, R. Lo Franco, G. Compagno, and G. Adesso, New J. Phys. 15, 093022 (2013).

[17] A. D’Arrigo, R. Lo Franco, G. Benenti, E. Paladino, and G. Falci, arXiv:1207.3294v2 (2014).

[18] R. Lo Franco, B. Bellomo, E. Andersson, and G. Compagno, Phys. Rev. A 85, 032318 (2012).

[19] J.-S. Xu, K. Sun, C.-F. Li, X.-Y. Xu, G.-C. Guo, E. Andersson, R. Lo Franco and G. Compagno, Nature Commun. 4, 2851 (2013).