Quantum entanglement of identical particles by standard information-theoretic notions

Quantum entanglement of identical particles is essential in quantum information theory. Yet, its correct determination remains an open issue hindering the general understanding and exploitation of many-particle systems. Operator-based methods have been developed that attempt to overcome the issue. We introduce a state-based method which, as second quantization, does not label identical particles and presents conceptual and technical advances compared to the previous ones. It establishes the quantitative role played by arbitrary wave function overlaps, local measurements and particle nature (bosons or fermions) in assessing entanglement by notions commonly used in quantum information theory for distinguishable particles, like partial trace. Our approach furthermore shows that bringing identical particles into the same spatial location functions as an entangling gate, providing fundamental theoretical support to recent experimental observations with ultracold atoms. These results pave the way to set and interpret experiments for utilizing quantum correlations in realistic scenarios where overlap of particles can count, as in Bose-Einstein condensates, quantum dots and biological molecular aggregates.Comment: 6+3 pages, 3 Figures. Stories on: Physics World (http://physicsworld.com/cws/article/news/2016/feb/12/theorists-disentangle-particle-identity); Phys.org (http://phys.org/news/2016-02-entanglement-identical-particles-doesnt-textbook.html). Invited article on 2Physics.com, presenting key developments in physics (http://www.2physics.com/2016/03/a-new-approach-to-quantum-entanglement.html

The Assessment of Thromboembolism Risk in Postbariatric Patient: Our Experience in 936 Patients

open3openTanzillo, Giuseppe; Vindigni, Vincenzo; Bassetto, FrancoTanzillo, Giuseppe; Vindigni, Vincenzo; Bassetto, Franc

Spin-echo entanglement protection from random telegraph noise

We analyze local spin-echo procedures to protect entanglement between two non-interacting qubits, each subject to pure-dephasing random telegraph noise. For superconducting qubits this simple model captures characteristic features of the effect of bistable impurities coupled to the device. An analytic expression for the entanglement dynamics is reported. Peculiar features related to the non-Gaussian nature of the noise already observed in the single qubit dynamics also occur in the entanglement dynamics for proper values of the ratio $g=v/\gamma$, between the qubit-impurity coupling strength and the switching rate of the random telegraph process, and of the separation between the pulses $\Delta t$. We find that the echo procedure may delay the disappearance of entanglement, cancel the dynamical structure of entanglement revivals and dark periods, and induce peculiar plateau-like behaviors of the concurrence.Comment: 9 pages, 2 figure

Pathwise uniqueness for stochastic reaction-diffusion equations in Banach spaces with an H\"{o}lder drift component

We prove pathwise uniqueness for an abstract stochastic reaction-diffusion equation in Banach spaces. The drift contains a bounded H\"{o}lder term; in spite of this, due to the space-time white noise it is possible to prove pathwise uniqueness. The proof is based on a detailed analysis of the associated Kolmogorov equation. The model includes examples not covered by the previous works based on Hilbert spaces or concrete SPDEs

Atomic spin sensitive dissipation on magnetic surfaces

We identify the mechanism of energy dissipation relevant to spin-sensitive nanomechanics including the recently introduced magnetic exchange force microscopy, where oscillating magnetic tips approach surface atomic spins. The tip-surface exchange couples spin and atom coordinates, leading to a spin-phonon problem with Caldeira-Leggett type dissipation. In the overdamped regime, that can lead to a hysteretic flip of the local spin with a large spin-dependent dissipation, even down to the very low experimental tip oscillation frequencies, describing recent observations for Fe tips on NiO. A phase transition to an underdamped regime with dramatic drop of magnetic tip dissipation should in principle be possible by tuning tip-surface distance.Comment: 4 pages, 4 figure

Comparison of non-Markovianity criteria in a qubit system under random external fields

We give the map representing the evolution of a qubit under the action of non-dissipative random external fields. From this map we construct the corresponding master equation that in turn allows us to phenomenologically introduce population damping of the qubit system. We then compare, in this system, the time-regions when non-Markovianity is present on the basis of different criteria both for the non-dissipative and dissipative case. We show that the adopted criteria agree both in the non-dissipative case and in the presence of population damping.Comment: 8 pages, 1 figure. Some changes made. In press on Physica Scripta T (special issue

On the finite size behavior of quantum collective spin systems

We discuss the finite size behavior of the adiabatic Dicke model, describing the collective coupling of a set of N-two level atoms (qubits) to a faster (electromagnetic) oscillator mode. The energy eigen-states of this system are shown to be directly related to those of another widely studied collective spin model, the uniaxial one. By employing an approximate continuum approach, we obtain a complete characterization of the properties of the latter, which we then use to evaluate the scaling properties of various observables for the original Dicke model near its quantum phase transition.Comment: 8 pages, 4 figure

Constants in Future Cities and Regions

The paper resumes some of the conversations the authors had in three years of research, based on the review of best participatory planning practices worldwide. The case projects are selected and discussed with the protagonists across four leading issues: Simulation, Scenario and Visioning, Government and Governance, and Scale. The case-oriented discussion is a peculiarity of the book , contributing to give shape to future cities or regions. The aim is to build a critical thinking on how urban planning, policy and design issues are faced differently or similarly throughout every cases studied. The book include the description of computer models and media, socio-political experiments and professional practices which help communicating the future effects of different design, policy and planning strategies and schemes with a wide range of aims: from information, through consultation, towards active participation. The cases have confirmed that simulation tools can impact on local government and can drive new forms of "glocal" governance, shaping and implementing future plans and projects at different scale and time span. The following paragraphs will point at some of the constant thoughts the authors had around the selection and editing of the book's case studied and related issue