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Fabrizio Buscemi

Publications and source records attributed to Fabrizio Buscemi.

At least 19 recordsLinked to original sources
arXiv2016

Non-Markovian continuous-time quantum walks on lattices with dynamical noise

We address the dynamics of continuous-time quantum walks on one-dimensional disordered lattices inducing dynamical noise in the system. Noise is described as time-dependent fluctuations of the tunneling amplitudes between adjacent sites, and attention is focused on non-Gaussian telegraph noise, going beyond the usual assumption of fast Gaussian noise. We observe the emergence of two different dynamical behaviors for the walker, corresponding to two opposite noise regimes: slow noise (i.e. strong coupling with the environment) confines the walker into few lattice nodes, while fast noise (weak coupling) induces a transition between quantum and classical diffusion over the lattice. A phase transition between the two dynamical regimes may be observed by tuning the ratio between the autocorrelation time of the noise and the coupling between the walker and the external environment generating the noise. We also address the non-Markovianity of the quantum map by assessing its memory effects, as well as evaluating the information backflow to the system. Our results suggest that the non-Markovian character of the evolution is linked to the dynamical behavior in the slow noise regime, and that fast noise induces a Markovian dynamics for the walker.

quant-ph↗
arXiv2016

Tailoring the core electron density in modulation-doped Core-Multi-Shell nanowires

We show how a proper radial modulation of the composition of core-multi-shell nanowires critically enhances the control of the free-carrier density in the high-mobility core with respect to core-single-shell structures, thus overcoming the technological difficulty of fine tuning the remote doping density. We calculate the electron population of the different nanowire layers as a function of the doping density and of several geometrical parameters by means of a self-consistent Schrödinger-Poisson approach: Free carriers tend to localize in the outer shell and screen the core from the electric field of the dopants.

cond-mat.mes-hall↗
arXiv2016

Quantum correlations of identical particles subject to classical environmental noise

In this work we propose a measure for the quantum discord of indistinguishable particles, based on the definition of entanglement of particles given in [H. M. Wiseman et al., Phis. Rev. Lett 91, 097902 (2003)]. This discord of particles is then used to evaluate the quantum correlations in a system of two identical bosons (fermions), where the particles perform a quantum random walk described by the Hubbard hamiltonian in a 1D lattice. The dynamics of the particles is either unperturbed or subject to a classical environmental noise - such as random telegraph, pink or brown noise. The observed results are consistent with those for the entanglement of particles, and we observe that on-site interaction between particles have an important protective effect on correlations against the decoherence of the system.

quant-ph↗
arXiv2015

Magneto-photoluminescence in GaAs/AlAs core-multishell nanowires: a theoretical investigation

The magneto-photoluminescence in modulation doped core-multishell nanowires is predicted as a function of photo-excitation intensity in non-perturbative transverse magnetic fields. We use a self-consistent field approach within the effective mass approximation to determine the photoexcited electron and hole populations, including the complex composition and anisotropic geometry of the nano-material. The evolution of the photoluminescence is analyzed as a function of i) photo-excitation power, ii) magnetic field intensity, iii) type of doping, and iv) anisotropy with respect to field orientation.

cond-mat.mes-hall↗
arXiv2015

Time-dependent simulation and analytical modelling of electronic Mach-Zehnder interferometry with edge-states wave packets

We compute the exact single-particle time-resolved dynamics of electronic Mach-Zehnder interferometers based on Landau edge-states transport, and assess the effect of the spatial localization of carriers on the interference pattern. The exact carrier dynamics is obtained by solving numerically the time-dependent Schroedinger equation with a suitable 2D potential profile reproducing the interferometer design. An external magnetic field, driving the system to the quantum Hall regime with filling factor one, is included. The injected carriers are represented by a superposition of edge states and their interference pattern reproduces the results of Y.Ji et al.[Nature 422, 415 (2003)]. By tuning the system towards different regimes, we find two additional features in the transmission spectra, both related to carrier localization, namely a damping of the Aharonov-Bohm oscillations with increasing difference in the arms length, and an increased mean transmission that we trace to the energy-dependent transmittance of quantum point contacts. Finally, we present an analytical model, also accounting for the finite spatial dispersion of the carriers, able to reproduce the above effects.

cond-mat.mes-hall↗
arXiv2014

Analytical expression of Genuine Tripartite Quantum Discord for Symmetrical X-states

The study of classical and quantum correlations in bipartite and multipartite systems is crucial for the development of quantum information theory. Among the quantifiers adopted in tripartite systems, the genuine tripartite quantum discord (GTQD), estimating the amount of quantum correlations shared among all the subsystems, plays a key role since it represents the natural extension of quantum discord used in bipartite systems. In this paper, we derive an analytical expression of GTQD for three-qubit systems characterized by a subclass of symmetrical X-states. Our approach has been tested on both GHZ and maximally mixed states reproducing the expected results. Furthermore, we believe that the procedure here developed constitutes a valid guideline to investigate quantum correlations in form of discord in more general multipartite systems.

quant-ph↗
arXiv2013

Quantum probes for the spectral properties of a classical environment

We address the use of simple quantum probes for the spectral characterization of classical noisy environments. In our scheme a qubit interacts with a classical stochastic field describing environmental noise and is then measured after a given interaction time in order to estimate the characteristic parameters of the noise. In particular, we address estimation of the spectral parameters of two relevant kinds of non-Gaussian noise: random telegraph noise with Lorentzian spectrum and colored noise with $1/f^α$ spectrum. We discuss the estimation precision achievable by quantum probes by analyzing in details the behavior of the quantum Fisher information (QFI) as a function of the noise and the other parameters. We found that population measurement on the qubit is optimal for noise estimation and also evaluate the optimal interaction times for the quantum probe, i.e. the values maximizing the QFI and the quantum signal-to-noise ratio. For random telegraph noise the QFI is inversely proportional to the square of the switching rate, meaning that the quantum signal-to-noise ratio is constant and thus the switching rate may be uniformly estimated with the same precision in its whole range of variation. For colored noise, the precision achievable in the estimation of ``color'', i.e. of the exponent $α$, strongly depends on the structure of the environment, i.e. on the number of fluctuators describing the classical environment. For an environment modeled by a single random fluctuator estimation is more precise for pink noise, i.e. for $α=1$, whereas by increasing the number of fluctuators, the QFI is has two local maxima, with the largest one drifting towards $α=2$, i.e. brown noise.

quant-ph↗
arXiv2013

Time-evolution of entanglement and quantum discord of bipartite systems subject to 1/f^α noise

We study the dynamics of quantum correlations for two non interacting qubits initially prepared in a maximally entangled state and then coupled with an external environment characterized by a noise spectrum of the form 1/f^α. The noise spectrum is due to the interaction of each qubit with a collection of N_f classical fluctuators with fixed switching rates. We find that, depending on the characteristic of the noise spectrum considered, both entanglement and quantum discord display either a monotonic decay or the phenomena of sudden death and revivals.

quant-ph↗
arXiv2013

Time-evolution of tripartite quantum discord and entanglement under local and non-local random telegraph noise

Few studies explored the dynamics of non-classical correlations besides entanglement in open multipartite quantum systems. Here, we address the time-evolution of quantum discord and entanglement in a model of three non-interacting qubits subject to a classical random telegraph noise in common and separated environments. Two initial entangled states of the system are examined, namely the GHZ- and W-type states. The dynamics of quantum correlations results to be strongly affected by the input configuration of the qubits, the type of the system-environment interaction, and the memory properties of the environmental noise. When the qubits are non-locally coupled to the random telegraph noise, the GHZ-type states partially preserve, at long times, both discord and entanglement, regardless the correlation time of the environmental noise. The survived entangled states turn out to be also detectable by means of suitable entanglement witnesses. On the other hand, in the same conditions, the decohering effects suppress all the quantum correlation of the W-type states which are thus less robust than the GHZ-type ones. The long-time survival of tripartite discord and entanglement opens interesting perspectives in the use of multipartite entangled states for practical applications in quantum information science.

quant-ph↗
arXiv2012

Electron interference and entanglement in coupled 1D systems with noise

We estimate the role of noise in the formation of entanglement and in the appearance of single- and two-electron interference in systems of coupled one-dimensional channels semiconductors. Two cases are considered: a single-particle interferometer and a two-particle interferometer exploiting Coulomb interaction. In both of them, environmental noise yields a randomization of the carrier phases. Our results assess how that the complementarity relation linking single-particle behavior to nonlocal quantities, such as entanglement and environment-induced decoherence, acts in electron interferometry. We show that, in a experimental implementation of the setups examined, one- and two-electron detection probability at the output drains can be used to evaluate the decoherence phenomena and the degree of entanglement.

cond-mat.mes-hall↗
arXiv2012

Effects of classical environmental noise on entanglement and quantum discord

We address the effect of classical noise on the dynamics of quantum correlations, entanglement and quantum discord, of two non-interacting qubits initially prepared in a Bell state. The effect of noise is modeled by randomizing the single-qubit transition amplitudes. We address both static and dynamic environmental noise corresponding to interaction with separate common baths in either Markovian and non-Markovian regimes. In the Markov regime, a monotone decay of the quantum correlations is found, whereas for non-Markovian noise sudden death and revival phenomena may occur, depending on the characteristics of the noise. Entanglement and quantum discord show the same qualitative behavior for all kind of noises considered. On the other hand, we find that separate and common environments may play opposite roles in preserving quantum correlations, depending on the noise regime considered.

quant-ph↗
arXiv2012

Hot-carrier trap-limited transport in switching chalcogenides

Chalcogenide materials have received great attention in the last decade owing to their application in new memory systems. Recently, phase-change memories have, in fact, reached the early stages of production. In spite of the industrial exploitation of such materials, the physical processes governing the switching mechanism are still debated. In this paper we work out a complete and consistent model for transport in amorphous chalcogenide materials based on trap-limited conduction accompanied by carrier heating. A previous model is here extended to include position-dependent carrier concentration and field, consistently linked by the Poisson equation. The results of the new model reproduce the experimental electrical characteristics and their dependences on the device length and temperature. Furthermore, the model provides a sound physical interpretation of the switching phenomenon and is able to give an estimate of the threshold condition in terms of the material parameters, a piece of information of great technological interest.

cond-mat.mtrl-sci↗
arXiv2012

Effect of Markov and Non-Markov Classical Noise on Entanglement Dynamics

We analyze the effect of a classical noise into the entanglement dynamics between two particles, initially entangled, subject to continuous time quantum walks in a one-dimensional lattice. The noise is modeled by randomizing the transition amplitudes from one site to another. Both Markovian and non-Markovian environments are considered. For the Markov regime an exponential decay of the initial quantum correlation is found, while the loss of coherence of the quantum state increases monotonically with time up to a saturation value depending upon the degrees of freedom of the system. For the non-Markov regime the presence or absence of entanglement revival and entanglement sudden death phenomena is found or deduced depending on the peculiar characteristics of the noise. Our results indicate that the entanglement dynamics in the non-Markovian regime is affected by the persistence of the memory effects of the environment and by its intrinsic features.

quant-ph↗
arXiv2012

Conduction, diffusion and noise of electrons in amorphous chalcogenides at low electric fields

The low-field electron diffusion, noise, and the conduction in amorphous chalcogenides are investigated by means of a Monte Carlo implementation of a full three- dimensional variable-range hopping transport model between localized states. Quantities like the carrier-velocity autocorrelation function, the noise power spectrum, the diffusion coefficient and the ohmic conductivity are obtained from numerical simulations at room temperatures and lower. Some interesting features of the linear-response regime typical of hopping transport are observed and discussed for the case of the amorphous Ge2Sb2Te5.

cond-mat.mtrl-sci↗
arXiv2012

Quantum correlations in continuos-time quantum walks of two indistinguishable particles

We evaluate the degree of quantum correlation between two fermions (bosons) subject to continuous time quantum walks in a one-dimensional ring lattice with periodic boundary conditions. In our approach, no particle-particle interaction is considered. We show that the interference effects due to exchange symmetry can result into the appearance of non-classical correlations. The role played onto the appearance of quantum correlations by the quantum statistics of the particles, the boundary conditions, and the partition of the system is widely investigated. Quantum correlations also been investigated in a model mimicking the ballistic evolution of two indistinguishable particles in a 1D continuous space structure. Our results are consistent with recent quantum optics and electron quantum optics experiments where the showing up of two-particle non-classical correlations has been observed even in the absence of mutual interaction between the particles.

quant-ph↗
arXiv2011

A measure of tripartite entanglement in bosonic and fermionic systems

We describe an efficient theoretical criterion suitable for the evaluation of the tripartite entanglement of any mixed three-boson or -fermion state, based on the notion of the entanglement of particles for bipartite systems of identical particles. Our approach allows one to quantify the accessible amount of quantum correlations in the systems without any violation of the local particle number superselection rule. A generalization of the tripartite negativity is here applied to some correlated systems including the continuous-time quantum walks of identical particles (both for bosons and fermions) and compared with other criteria recently proposed in the literature. Our results show the dependence of the entanglement dynamics upon the quantum statistics: the bosonic bunching results into a low amount of quantum correlations while Fermi-Dirac statistics allows for higher values of the entanglement.

quant-ph↗
arXiv2010

Shor's quantum algorithm using electrons in semiconductor nanostructures

Shor's factoring algorithm illustrates the potential power of quantum computation. Here we present and numerically investigate a proposal for a compiled version of such an algorithm based on a quantum-wire network exploiting the potentialities of fully coherent electron transport assisted by the surface acoustic waves. Specifically, a non standard approach is used to implement, in a simple form, the quantum circuits of the modular exponentiation execution for the simplest instance of the Shor's algorithm, that is the factorization of $N$=15. The numerical procedure is based on a time-dependent solution of the multi-particle Schrödinger equation. The near-ideal algorithm performance and the large estimated fidelity indicate the efficiency of the protocol implemented, which also results to be almost unsensitive to small destabilizing effects during quantum computation.

quant-ph↗