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Characterizzation of dynamical properties of non-Markovian open quantum systems
Full text linkIn the present Thesis we study the behavior of multi-time correlation functions and of thermodynamical quantities such as heat in open quantum systems undergoing an evolution generally affected by the presence of memory effects, i.e. non-Markovian. In the last decade, a large part of the scientific community in this field has dedicated its efforts to the understanding, precise definition and quantification of non-Markovianity in the quantum realm and now we have at our disposal several benchmark results and a plethora of different estimators that allow to determine the degree of non-Markovianity of a given dynamics. It comes therefore natural to investigate how other different dynamical quantities relate to such estimators also in order to understand the physical implications of memory effects on the statistics of observable quantities.
In the first part of this work, a quantitative test of the violation of the so-called quantum regression theorem in presence of a non-Markovian dynamical regime is investigated. The quantum regression theorem represents a procedure that, whenever valid, allows to reconstruct two-time correlation functions of system's operators from the sole knowledge of the dynamics of mean values. It is worth stressing that two-time correlation functions are necessary in order to fully characterize the statistical properties of a quantum system, since they are able to catch aspects of the dynamics, such as fluorescence spectrum, in general not accessible looking at mean values. Despite their relevance however, obtaining two-time correlation functions often represents a formidable task, since the knowledge of the full "system+environment" dynamics is required, a generally too demanding request in the context of open quantum systems theory. The quantum regression theorem represents in this regard the easiest route to determine two-time correlation functions, this highlighting its importance. In this work we show that, in a pure-dephasing spin-boson model, the quantum regression theorem represents a stronger condition than non-Markovianity, in the sense that any presence of memory effects in the reduced dynamics inevitably results in violations to the former. These results have been published in [G.Guarnieri, A. Smirne, B. Vacchini, Phys. Rev. A 90, 022110 (2014)].
The second part of the Thesis is devoted to the characterization of heat ow at the microscopic level in open quantum systems, both finite and infinite dimensional. In particular we begin by studying the time behavior of its mean value in a non-Markovian dynamical regime, showing that, at variance
with what happens in the Born-Markov semigroup limiting case, heat can backflow from the environment to the system. After providing a condition for the occurrence of such phenomenon and a measure for its amount for a given dynamics, the relationship with suitable non-Markovianity estimators is sought in two paradigmatic models, namely the spin-boson and the quantum brownian motion. The results, collected in [ G. Guarnieri, C. Uchiyama, B. Vacchini, Phys. Rev. A 93, 012118 (2016); G. Guarnieri, J. Nokkala, R. Schmidt, S. Maniscalco, B. Vacchini, Phys. Rev. A 94, 062101 (2016)], on the one hand allow for the identification of parameter-regions where the heat backflow is absent or maximum. On the other hand they show that the occurrence of heat backflow represents a stricter condition than non-Markovianity, in the sense that non-Markovianity allows for the observation of heat flowing back from the environment to the system and, vice versa, a Markovian dynamics prevents its occurrence. This Thesis concludes with the formulation of a new family of lower bounds to the mean dissipated heat in an environmental-assisted erasure-protocol scenario where Landauer's principle applies. As originally conceived for classical systems, this principle states that every irreversible erasure of information stored in a system inevitably carries along an amount of heat dissipated into the environment which is expended to perform the action. Within the framework recently put forward in [D. Reeb, M. M. Wolf, New J. Phys. 16, 103011 (2014)],
which guarantees the validity of Landauer's principle in an open quantum systems scenario, we provide an asymptotically tight family of lower bounds to the dissipated heat which are also valid in the non-equilibrium setting. This construction is applied to an open system consisting of a three-level V-system, in which one transition is externally pumped by a laser field while the other is coupled through an XX-interaction to an environment consisting of a spin chain. Beside calculating all these quantities, an exact solution for the dynamics of such system is also provided. These results are collected in [G. Guarnieri, S. Campbell, J. Goold, S. Pigeon, M. Paternostro, B. Vacchini, in preparation]
Inapplicabilità dell'art.420 bis in grado d'appello, commento a Cass. sez. lav. 7 marzo 2007 - n.5230 e 19 febbraio 2007 n. 3770
No full textLe sezioni Unite optano per la "sopravvivenza" del ricorso incidentale tardivo in caso di rinuncia al ricorso principale. comm. a S.U. 19 aprile 2011, n. 8925
No full textViene commentato, in senso parzialmente favorevole, il nuovo orientamento delle Sezioni Unite in tema di inammissibilità e improcedibilità del ricorso incidentale tardivo in casazion
Querela di falso in appello, sospensione del processo e regolamento di competenza, nota a Cass., Sez. lav. 22 novembre 2011, n.24621
No full textGiudizio di cassazione e onere di depositare il testo integrale del contratto o accordo collettivo - nota a Cass. S.U. 23 settembre 2010, n. 20075
No full textTentativo obbligatorio di conciliazione: legittimità costituzionale dell'art. 410 bis, comma 2, c.p.c. commento a Corte cost. 26 ottobre 2007 n. 355
No full textNotifica del ricorso in appello: svolta rigorosa delle S.U. e della Sezione lavoro, commento a Cass., S.U., 30 lugli8o 2008 n. 20604 e Cass., Sez. Lav., 12 settembre 2008, n.23571
No full textSentenza "non definitiva" ex art. 64 del T.U. 165/01 e giudicato implicito sulla giurisdizione, commento a Cass., S.U., 19 ottobre 2006, n. 22427
No full textTentativo obbligatorio di conciliazione : legittimità ostituzionale dell'art. 410 bis, comma 2, c.p.c.
No full textFase sommaria del rito Fornero e proponibilità dei regolamenti di giurisdizione e competenza
No full textIl commento prende in esame due ordinanze delle Sezioni Unite del 2014, la n.17433 e la n.19674, che, in armonia tra loro, hanno rispettivamente ritenuto impugnabile con regolamento di competenza una pronuncia sulla litispendenza emessa al termine della fase sommaria nell’ambito del c.d. rito Fornero (art. 1, commi 47 ss. della legge n.92 del 2012), ed esperibile il regolamento di giurisdizione già nell’ambito della stessa fase sommaria. L’A. approva le soluzioni accolte e aggiunge che, con analoghe motivazioni, dovrebbe altresì affermarsi che, ai sensi dell’art. 51, primo comma, n. 4, c.p.c., il giudice-persona fisica della fase sommaria non possa poi essere anche il giudice della eventuale fase di opposizione
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