Advances in two and three-phase bubble columns modeling: large eddy simulation and population balance

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Off-resonant entanglement generation in a lossy cavity

We provide an exact and complete characterization of the entanglement dynamics of two qubits coupled to a common structured reservoir at zero temperature. We derive the conditions to maximize reservoir-induced entanglement for an initially factorized state of the two-qubit system. In particular, when the two qubits are placed inside a lossy cavity, we show that high values of entanglement can be obtained, even in the bad cavity limit, in the dispersive regime. Finally we show that, under certain conditions, the entanglement dynamics exhibits quantum beats and we explain their physical origin in terms of the interference between two different transitions coupling the dressed states of the system.Comment: 10 pages, 6 figure

Protecting entanglement via the quantum Zeno effect

We study the exact entanglement dynamics of two atoms in a lossy resonator. Besides discussing the steady-state entanglement, we show that in the strong coupling regime the system-reservoir correlations induce entanglement revivals and oscillations and propose a strategy to fight against the deterioration of the entanglement using the quantum Zeno effect.Comment: 4 pages, 3 figure

Non-Markovian dynamics of system-reservoir entanglement

Using an exact approach, we study the dynamics of entanglement between two qubits coupled to independent reservoirs and between the two, initially disentangled, reservoirs. We also describe the transfer of bipartite entanglement from the two-qubits to their respective reservoirs focussing on the case of two atoms inside two different leaky cavities with a specific attention to the role of the detuning. We present a scheme to prepare the cavity fields in a maximally entangled state, without direct interaction between the cavities, by exploiting the initial qubits entanglement. We discuss a deterministic protocol, working in the presence of cavity losses, for the generation of a W-state of one qubit and two cavity fields and we describe a probabilistic scheme to entangle one of the atoms with the reservoir (cavity field) of the other atom

Dynamical decoupling efficiency versus quantum non-Markovianity

We investigate the relationship between non-Markovianity and the effectiveness of a dynamical decoupling protocol for qubits undergoing pure dephasing. We consider an exact model in which dephasing arises due to a bosonic environment with a spectral density of the Ohmic class. This is parametrised by an Ohmicity parameter by changing which we can model both Markovian and non-Markovian environments. Interestingly, we find that engineering a non-Markovian environment is detrimental to the efficiency of the dynamical decoupling scheme, leading to a worse coherence preservation. We show that each dynamical decoupling pulse reverses the flow of quantum information and, on this basis, we investigate the connection between dynamical decoupling efficiency and the reservoir spectral density. Finally, in the spirit of reservoir engineering, we investigate the optimum system-reservoir parameters for achieving maximum stationary coherences.Comment: 6 pages, 4 figure

A New Interpretation of the Edicts of Aśoka from Kandahar

From Alexandria of Arachosia, present-day Kandahar, we have two edicts in Greek, issued by the sovereign Maurya Aśoka (c. 270-230 BC). Arachosia, the ancient Eastern satrapy of the Achaemenid Empire – corresponding to present-day southeastern Afghanistan – had long seen the meeting of the Iranian world to the west and the Indian world to the east. As from the end of the fourth century BC, after the conquest by Alexander the Great and the occupation of the eastern dominions of the Empire by Seleucus Nicator, it was to see a conspicuous Greek presence, strikingly attested by the epigraphs of Aśoka. The first edict – discovered in 1957 – is in two languages, Greek and Aramaic, while the second – discovered in 1963 – is in Greek alone. On the basis of texts from the court of Maurya of Pāṭaliputra, both of them constitute summaries of and propaganda for the conversion and moral principles inspiring Aśoka, subsequent to his bloody conquest of Kaliṅga. Our aim here is to take stock of certain issues, proposing a new completion for the opening lacuna in the Greek section of the bilingual epigraph, and casting doubt anew on the originality of the Greek texts, considering the attribution of the region to Indian, rather than Seleucid rule after the pact between Seleucus Nicator and Candragupta Maurya, Aśoka's grandfather (c. 305 BC)

Non-Markovian dynamics of a qubit

In this paper we investigate the non-Markovian dynamics of a qubit by comparing two generalized master equations with memory. In the case of a thermal bath, we derive the solution of the post-Markovian master equation recently proposed in Ref. [A. Shabani and D.A. Lidar, Phys. Rev. A {\bf 71}, 020101(R) (2005)] and we study the dynamics for an exponentially decaying memory kernel. We compare the solution of the post-Markovian master equation with the solution of the typical memory kernel master equation. Our results lead to a new physical interpretation of the reservoir correlation function and bring to light the limits of usability of master equations with memory for the system under consideration.Comment: Replaced with published version (minor changes