Special Issue “Machine Learning in Insurance”

Learning in Insurance”, which represents a compilation of ten high-quality articles discussing avant-garde developments or introducing new theoretical or practical advances in this field

Hubbard model as an approximation to the entanglement in nanostructures

We investigate how well the one-dimensional Hubbard model describes the entanglement of particles trapped in a string of quantum wells. We calculate the average single-site entanglement for two particles interacting via a contact interaction and consider the effect of varying the interaction strength and the interwell distance. We compare the results with the ones obtained within the one-dimensional Hubbard model with on-site interaction. We suggest an upper bound for the average single-site entanglement for two electrons in M wells and discuss analytical limits for very large repulsive and attractive interactions. We investigate how the interplay between interaction and potential shape in the quantum-well system dictates the position and size of the entanglement maxima and the agreement with the theoretical limits. Finally, we calculate the spatial entanglement for the quantum-well system and compare it to its average single-site entanglement

Weak measurement and control of entanglement generation

In this paper we show how weak joint measurement and local feedback can be used to control entanglement generation between two qubits. To do this, we make use of a decoherence free subspace (DFS). Weak measurement and feedback can be used to drive the system into this subspace rapidly. Once within the subspace, feedback can generate entanglement rapidly, or turn off entanglement generation dynamically. We also consider, in the context of weak measurement, some of differences between purification and generating entanglement

MiniBooNE and a (CP)^2 = -1 sterile neutrino

It has been taken as granted that the observation of two independent mass-squared differences necessarily fixes the number of underlying mass eigenstates as three, and that the addition of a sterile neutrino provides an additional mass-squared difference. The purpose of this Letter is to argue that if one considers a sterile neutrino component that belongs to the (CP)^2 = - 1 sector, then both of the stated claims are false. We also outline how the results reported here, when combined with the forthcoming MiniBooNE data and other experiments, can help settle the issue of the CP properties of the sterile neutrino; if such a component does indeed exist.Comment: Mod. Phys. Lett. A (in press, 8 pages

On the energy dependence of the D^+/D^- production asymmetry

In this paper we discuss the origin of the asymmetry present in D meson production and its energy dependence. In particular, we have applied the meson cloud model to calculate the asymmetries in D^-/D^+ meson production in high energy p-p collisions and find a good agreement with recent LHCb data. Although small, this non-vanishing asymmetry may shed light on the role played by the charm meson cloud of the proton.Comment: 8 pages, 8 figures. arXiv admin note: text overlap with arXiv:hep-ph/000927

Evolutional Entanglement in Nonequilibrium Processes

Entanglement in nonequilibrium systems is considered. A general definition for entanglement measure is introduced, which can be applied for characterizing the level of entanglement produced by arbitrary operators. Applying this definition to reduced density matrices makes it possible to measure the entanglement in nonequilibrium as well as in equilibrium statistical systems. An example of a multimode Bose-Einstein condensate is discussed.Comment: 10 pages, Late

Multipartite entanglement in the Fenna-Matthews-Olson (FMO) pigment-protein complex

We investigate multipartite states in the Fenna-Matthews-Olson (FMO) pigment-protein complex of the green sulfur bacteria using a Lorentzian spectral density of the phonon reservoir fitted with typical parameter estimates of the species, P. aestuarii. The evolution of the entanglement measure of the excitonic W qubit states is evaluated in the picosecond time range, showing increased revivals in the non-Markovian regime. Similar trends are observed in the evolution dynamics of the Meyer-Wallach measure of the N-exciton multipartite state, with results showing that multipartite entanglement can last from 0.5 to 1 ps, between the Bchls of the FMO complex. The teleportation and quantum information splitting fidelities associated with the GHZ and W_A resource states of the excitonic qubit channels of the FMO complex show that revivals in fidelities increase with the degree of non-Markovian strength of the decoherent environment. Results indicate that quantum information processing tasks involving teleportation followed by the decodification process involving W_A states of the FMO complex, may play a critical role during coherent oscillations at physiological temperatures.Comment: 16 pages, new figs, typo

Computation by measurements: a unifying picture

The ability to perform a universal set of quantum operations based solely on static resources and measurements presents us with a strikingly novel viewpoint for thinking about quantum computation and its powers. We consider the two major models for doing quantum computation by measurements that have hitherto appeared in the literature and show that they are conceptually closely related by demonstrating a systematic local mapping between them. This way we effectively unify the two models, showing that they make use of interchangeable primitives. With the tools developed for this mapping, we then construct more resource-effective methods for performing computation within both models and propose schemes for the construction of arbitrary graph states employing two-qubit measurements alone.Comment: 13 pages, 18 figures, REVTeX

Qubit rotation and Berry Phase

A quantized fermion can be represented by a scalar particle encircling a magnetic flux line. It has the spinor structure which can be constructed from quantum gates and qubits. We have studied here the role of Berry phase in removing dynamical phase during one qubit rotation of a quantized fermion. The entanglement of two qubit inserting spin-echo to one of them results the change of Berry phase that can be considered as a measure of entanglement. Some effort is given to study the effect of noise on the Berry phase of spinor and their entangled states.Comment: 12 page

Dynamics of entanglement in quantum computers with imperfections

The dynamics of the pairwise entanglement in a qubit lattice in the presence of static imperfections exhibits different regimes. We show that there is a transition from a perturbative region, where the entanglement is stable against imperfections, to the ergodic regime, in which a pair of qubits becomes entangled with the rest of the lattice and the pairwise entanglement drops to zero. The transition is almost independent of the size of the quantum computer. We consider both the case of an initial maximally entangled and separable state. In this last case there is a broad crossover region in which the computer imperfections can be used to create a significant amount of pairwise entanglement.Comment: 4 pages, 4 figure