Search results for "OPEN QUANTUM SYSTEMS"
showing 10 items of 69 documents
Dynamics of geometric and entropic quantifiers of correlations in open quantum systems
2012
We extend the Hilbert-Schmidt (square norm) distance, previously used to define the geometric quantum discord, to define also geometric quantifiers of total and classical correlations. We then compare the dynamics of geometric and entropic quantifiers of the different kinds of correlations in a non-Markovian open two-qubit system under local dephasing. We find that qualitative differences occur only for quantum discords. This is taken to imply that geometric and entropic discords are not, in general, equivalent in describing the dynamics of quantum correlations. We then show that also geometric and entropic quantifiers of total correlations present qualitative disagreements in the state spa…
Master equations for two qubits coupled via a nonlinear mode
2013
A microscopic master equation describing the dynamics of two qubits coupled via a nonlinear mediator is constructed supposing that the two qubits, as well as the nonlinear mode, interact, each with its own independent bosonic bath. Generally speaking the master equation derived in this way represents a more appropriate tool for studying the dynamics of open quantum systems. Indeed we show that it is more complex than the phenomenological master equation, constructed simply adding ad hoc dissipative terms.
Stochastic collision model approach to transport phenomena in quantum networks
2021
Abstract Noise-assisted transport phenomena highlight the nontrivial interplay between environmental effects and quantum coherence in achieving maximal efficiency. Due to the complexity of biochemical systems and their environments, effective open quantum system models capable of providing physical insights on the presence and role of quantum effects are highly needed. In this paper, we introduce a new approach that combines an effective quantum microscopic description with a classical stochastic one. Our stochastic collision model (SCM) describes both Markovian and non-Markovian dynamics without relying on the weak coupling assumption. We investigate the consequences of spatial and tempora…
Long-Time Preservation of Nonlocal Entanglement
2009
We investigate how nonlocal entanglement, as identified by violations of a Bell inequality, may be preserved during the evolution. Our system consists of two qubits each embedded in a zero-temperature bosonic reservoir evolving independently and initially in an entangled mixed state. We show that the violation of the Bell inequality can be related to the single-qubit population of excited state in such a way that, by appropriately choosing structured environments that give rise to sufficiently high values of population trapping, long-time preservation of nonlocal entanglement can be correspondingly achieved.
A geometric analysis of the effects of noise on Berry phase
2007
In this work we describe the effect of classical and quantum noise on the Berry phase. It is not a topical review article but rather an overview of our work in this field aiming at giving a simple pictorial intuition of our results.
Photon localization versus population trapping in a coupled-cavity array
2014
We consider a coupled-cavity array (CCA), where one cavity interacts with a two-level atom under the rotating-wave approximation. We investigate the excitation transport dynamics across the array, which arises in the atom's emission process into the CCA vacuum. Due to the known formation of atom-photon bound states, partial field localization and atomic population trapping in general take place. We study the functional dependance on the coupling strength of these two phenomena and show that the threshold values beyond which they become significant are different. As the coupling strength grows from zero, field localization is exhibited first.
The bistable potential: An archetype for classical and quantum systems
2012
In this work we analyze the transient dynamics of three different classical and quantum systems. First, we consider a classical Brownian particle moving in an asymmetric bistable potential, subject to a multiplicative and additive noise source. We investigate the role of these two noise sources on the life time of the metastable state. A nonmonotonic behavior of the lifetime as a function of both additive and multiplicative noise intensities is found, revealing the phenomenon of noise enhanced stability. Afterward, by using a LotkaVolterra model, the dynamics of two competing species in the presence of Lévy noise sources is analyzed. Quasiperiodic oscillations and stochastic resonance pheno…
Switching quantum memory on and off
2015
Modifying the Markovian (memoryless) or non-Markovian (memory-keeping) nature of the environment-induced evolution of an open quantum system is crucial in quantum information theory, because it is linked to quantum memory control. A recent work (Brito and Werlang 2015 New J. Phys. 17 072001) shows that such a goal can be achieved without operating on unaccessible environmental features. In fact, transitions between Markovian and non-Markovian regimes of a qubit dynamics can be induced on demand if the qubit is coupled to a controlled auxiliary system. This is a step towards the improvement of quantum devices, aiming at exploiting dynamical memory effects by an external control.
Master equation for cascade quantum channels: a collisional approach
2012
It has been recently shown that collisional models can be used to derive a general form for the master equations which describe the reduced time evolution of a composite multipartite quantum system, whose components "propagate" in an environmental medium which induces correlations among them via a cascade mechanism. Here we analyze the fundamental assumptions of this approach showing how some of them can be lifted when passing into a proper interaction picture representation.
Light-induced anomalous Hall effect in massless Dirac fermion systems and topological insulators with dissipation
2019
Employing the quantum Liouville equation with phenomenological dissipation, we investigate the transport properties of massless and massive Dirac fermion systems that mimics graphene and topological insulators, respectively. The massless Dirac fermion system does not show an intrinsic Hall effect, but it shows a Hall current under the presence of circularly-polarized laser fields as a nature of a optically-driven nonequilibrium state. Based on the microscopic analysis, we find that the light-induced Hall effect mainly originates from the imbalance of photocarrier distribution in momentum space although the emergent Floquet–Berry curvature also has a non-zero contribution. We further compute…