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.Comment: 19 pages, 3 figure

Contractual Testing

Variants of must testing approach have been successfully applied in Service Oriented Computing for capturing compliance between (contracts exposed by) a client and a service and for characterising safe replacement, namely the fact that compliance is preserved when a service exposing a ’smaller’ contract is replaced by another one with a ’larger’ contract. Nevertheless, in multi-party interactions, partners often lack full coordination capabilities. Such a scenario calls for less discriminating notions of testing in which observers are, e.g., the description of uncoordinated multiparty contexts or contexts that are unable to observe the complete behaviour of the process under test. In this paper we propose an extended notion of must preorder, called contractual preorder, according to which contracts are compared according to their ability to pass only the tests belonging to a given set. We show the generality of our framework by proving that preorders induced by existing notions of compliance in a distributed setting are instances of the contractual preorder when restricting to suitable sets of observers

Dynamics of quantum correlations in colored environments

We address the dynamics of entanglement and quantum discord for two non interacting qubits initially prepared in a maximally entangled state and then subjected to a classical colored noise, i.e. coupled with an external environment characterized by a noise spectrum of the form $1/f^{\alpha}$. More specifically, we address systems where the Gaussian approximation fails, i.e. the sole knowledge of the spectrum is not enough to determine the dynamics of quantum correlations. We thus investigate the dynamics for two different configurations of the environment: in the first case the noise spectrum is due to the interaction of each qubit with a single bistable fluctuator with an undetermined switching rate, whereas in the second case we consider a collection of classical fluctuators with fixed switching rates. In both cases we found analytical expressions for the time dependence of entanglement and quantum discord, which may be also extended to a collection of flcutuators with random switching rates. The environmental noise is introduced by means of stochastic time-dependent terms in the Hamiltonian and this allows us to describe the effects of both separate and common environments. We show that the non-Gaussian character of the noise may lead to significant effects, e.g. environments with the same power spectrum, but different configurations, give raise to opposite behavior for the quantum correlations. In particular, depending on the characteristics of the environmental noise considered, both entanglement and discord display either a monotonic decay or the phenomena of sudden death and revivals. Our results show that the microscopic structure of environment, besides its noise spectrum, is relevant for the dynamics of quantum correlations, and may be a valid starting point for the engineering of non-Gaussian colored environments.Comment: 8 pages, 3 figure

Physical activity and cardiovascular prevention: Is healthy urban living a possible reality or utopia?

Favoring correct lifestyles is the most important measure to contrast cardiovascular diseases and the epidemic of high cardiovascular risk conditions, such as obesity, diabetes, and hypertension. Lifestyle is a broad expression that includes diet, physical exercise, and psychological and socio-economic factors, each of which must be taken into due consideration because of their intertwining influences, which may be a barrier to healthy changes at both the individual and population levels. While physical activity has probably received less attention in the last decades, it is likely the most important among the modifiable risk factors for cardiovascular diseases. Improving the habitual physical activity level is an achievable goal, and even small improvements may have important favorable effects on health. Strategies at the population level have to be urgently taken, and involve not only public health, but also administrators and politicians, starting from a rethinking of our cities

Physical realizations of quantum operations

Quantum operations (QO) describe any state change allowed in quantum mechanics, such as the evolution of an open system or the state change due to a measurement. We address the problem of which unitary transformations and which observables can be used to achieve a QO with generally different input and output Hilbert spaces. We classify all unitary extensions of a QO, and give explicit realizations in terms of free-evolution direct-sum dilations and interacting tensor-product dilations. In terms of Hilbert space dimensionality the free-evolution dilations minimize the physical resources needed to realize the QO, and for this case we provide bounds for the dimension of the ancilla space versus the rank of the QO. The interacting dilations, on the other hand, correspond to the customary ancilla-system interaction realization, and for these we derive a majorization relation which selects the allowed unitary interactions between system and ancilla.Comment: 8 pages, no figures. Accepted for publication on Phys. Rev.

A minimum-disturbing quantum state discriminator

We propose two experimental schemes for quantum state discrimination that achieve the optimal tradeoff between the probability of correct identification and the disturbance on the quantum state.Comment: 9 pages, 1 figure, OSID style. Submitted to the special issue of "Open Systems and Information Dynamics", Proceedings of the "38th Symposium on Mathematical Physics", Torun, Poland, June 200

Information-Disturbance Tradeoff in Quantum State Discrimination

When discriminating between two pure quantum states, there exists a quantitative tradeoff between the information retrieved by the measurement and the disturbance caused on the unknown state. We derive the optimal tradeoff and provide the corresponding quantum measurement. Such an optimal measurement smoothly interpolates between the two limiting cases of maximal information extraction and no measurement at all.Comment: 5 pages, 2 (low-quality) figures. Eq. (20) corrected. Final published versio

Improving information/disturbance and estimation/distortion trade-offs with non universal protocols

We analyze in details a conditional measurement scheme based on linear optical components, feed-forward loop and homodyne detection. The scheme may be used to achieve two different tasks. On the one hand it allows the extraction of information with minimum disturbance about a set of coherent states. On the other hand, it represents a nondemolitive measurement scheme for the annihilation operator, i.e. an indirect measurement of the Q-function. We investigate the information/disturbance trade-off for state inference and introduce the estimation/distortion trade-off to assess estimation of the Q-function. For coherent states chosen from a Gaussian set we evaluate both information/disturbance and estimation/distortion trade-offs and found that non universal protocols may be optimized in order to achieve better performances than universal ones. For Fock number states we prove that universal protocols do not exist and evaluate the estimation/distortion trade-off for a thermal distribution.Comment: 10 pages, 6 figures; published versio

Characterization of metabolically healthy obese people and metabolically unhealthy normal-weight people in a general population cohort of the ABCD Study

There is actually no consensus about the possibility that in some instances, obesity may be a benign metabolically healthy (MH) condition as opposed to a normal-weight but metabolically unhealthy (MUH) state. The aim of this study was to characterize MH condition and to investigate possible associations with metabolic and cardiovascular complications. One thousand nineteen people (range of age 18-90 years) of the cohort of the ABCD-2 study were investigated. Participants were classified as normal weight (BMI < 24.9 kg/m2) or overweight-obese (BMI \ue2\u89\ua525 kg/m2); they were also classified as MH in the presence of 0-1 among the following conditions: (a) prediabetes/type 2 diabetes, (b) hypertension, (c) hypertriglyceridemia or low HDL cholesterolemia, and (d) hypercholesterolemia. MUH condition was diagnosed if \ue2\u89\ua52 of the conditions listed were found. The prevalence of overweight/obese people was 71.1%, of whom 27.4% were found to be MH. In addition, 36.7% of the normal-weight participants were MUH. HOMA-IR, high sensitivity C-reactive protein, and the carotid intima-media thickness were significantly different in the 4 subgroups (P < 0.001), with higher values observed in the MUH normal-weight and obese groups. In conclusion, this study highlights the importance of identifying a MH condition in normal-weight and in obese people in order to offer better treatment