State Of Composite System Research Articles

Escaping social–ecological traps through ecological restoration and socioeconomic development in China's Loess Plateau

Abstract The social–ecological trap is an emerging concept that describes situations in which self‐reinforcing social and ecological feedbacks maintain or push a social–ecological system towards an undesirable state and threaten the sustainability of human societies. Understanding a system's feedback loops and identifying the leading factors of such traps is essential to develop effective management strategies to warn, avoid and escape traps. To better understand the dynamics of social–ecological traps, we developed a quantitative diagnostic framework that combines the social–ecological network approach and composite system state index. We demonstrated the effectiveness of the framework by examining the rural social–ecological evolution in China's Loess Plateau (LP) from 1949 to 2020, an area once faced with severe social–ecological challenges such as soil erosion, land degradation and poverty. Our analysis identified three stages of trap dynamics in LP: locked in the trap (1949–1981), reacting to the trap (1981–2003) and escaping the trap (2003–2020). In the first stage, LP was locked into an undesirable trajectory where reinforcing feedback occurs between rapid population growth, limited livelihood opportunities, excessive reliance on agriculture and severe soil erosion. Our results also found that the LP has made significant progress in escaping this social–ecological trap during the 21st century through ecological restoration practices and socioeconomic development. Similar social–ecological traps are also observed in many other regions of the world, particularly in developing countries. Our analysis recommends three pathways for addressing social–ecological traps in the LP: (1) promoting urbanization and livelihood diversity, (2) implementing site‐specific engineering measures (e.g. terraces and check dams in the LP) and (3) investing in ecological restoration programs. Escaping the trap is not the end of the story, but could be an early stage of another trap. Policymakers and managers should keep assessing and monitoring the policy practices and outcomes to avoid entering new trap situations. Read the free Plain Language Summary for this article on the Journal blog.

Research methods for social-ecological traps through composite system state index and social-ecological network

Research methods for social-ecological traps through composite system state index and social-ecological network

Classicality without local discriminability: Decoupling entanglement and complementarity

An operational probabilistic theory where all systems are classical, and all pure states of composite systems are entangled, is constructed. The theory is endowed with a rule for composing an arbitrary number of systems, and with a nontrivial set of transformations. Hence, we demonstrate that the presence of entanglement is independent of the existence of incompatible measurements. We then study a variety of phenomena occurring in the theory -- some of them contradicting both Classical and Quantum Theories -- including: cloning, entanglement swapping, dense coding, additivity of classical capacities, non-monogamous entanglement, hypersignaling. We also prove the existence, in the theory, of a universal processor. The theory is causal and satisfies the no-restriction hypothesis. At the same time, it violates a number of information-theoretic principles enjoyed by Quantum Theory, most notably: local discriminability, purity of parallel composition of states, and purification. Moreover, we introduce an exhaustive procedure to construct generic operational probabilistic theories, and a sufficient set of conditions to verify their consistency. In addition, we prove a characterisation theorem for the parallel composition rules of arbitrary theories, and specialise it to the case of bilocal-tomographic theories. We conclude pointing out some open problems. In particular, on the basis of the fact that every separable state of the theory is a statistical mixture of entangled states, we formulate a no-go conjecture for the existence of a local-realistic ontological model.

Separating Einstein's separability

In this paper, I accomplish a conceptual task and a historical task. The conceptual task is to argue that (1) Einstein's Principle of Separability (henceforth “separability”) is not a supervenience principle and that (2) separability and entanglement are compatible. I support (1) by showing that the conclusion of Einstein's incompleteness argument would still follow even if one assumes that the state of a composite system does not supervene on the states of the subsystems, and by showing that what Einstein says in “Quantum Mechanics and Reality” (1948) strongly suggests that separability is not a principle about how subsystem states relate to the state of composite systems. I support (2) by showing that if separability was incompatible with entanglement, then Einstein's argument would be incoherent in a trivial way. Thus, by arguing for (1) and (2) I directly challenge what has been, and still is, a very common reading of separability. The historical task is to offer the first detailed review of the different ways in which separability has been defined by physicists and philosophers in the last 60 years. Among other things, such a review distinguishes three different definitions of the principle, and shows that since the 1990s and up until the present date, it became standard to take separability (as presented by Einstein) to be a supervenience principle.

Information as a physical quantity

A new physical conception of classical information in quantum mechanical systems is explicated, critically assessed, and formalized in a quantitative measure. Observer-local referential (OLR) information—a shared physical property of entities accessible to a specified observer—is defined on the joint states of composite systems, distinguished from related conceptions of information, and tested against strict criteria that would simultaneously qualify it as a physical state quantity and as a meaningful measure of classical information. It is shown specifically to satisfy these criteria in the technological context of digital computation on quantum-physical substrates, where familiar alternatives—the von Neumann entropy and quantum mutual information (or correlation entropy)— fall short. The OLR conception provides a natural foundation for the fundamental physical description of information processing in digital computing systems, both because it defines information as a physical state quantity—placing it on an equal footing with other physical quantities appearing in such descriptions—and because it captures essential features of information in computational contexts that alternative physical conceptions do not. The OLR information measure enables straightforward and thoroughly physical quantification of digital information in general quantum systems and processes, enabling unambiguous determination of bounds on physical costs of generally noisy digital computation. More generally, OLR information offers a physical foundation for information that does not require the physical to be—ontologically or metaphorically—already informational.

On the equivalence of separability and extendability of quantum states

Motivated by the notions of [Formula: see text]-extendability and complete extendability of the state of a finite level quantum system as described by Doherty et al. [Complete family of separability criteria, Phys. Rev. A 69 (2004) 022308], we introduce parallel definitions in the context of Gaussian states and using only properties of their covariance matrices, derive necessary and sufficient conditions for their complete extendability. It turns out that the complete extendability property is equivalent to the separability property of a bipartite Gaussian state. Following the proof of quantum de Finetti theorem as outlined in Hudson and Moody [Locally normal symmetric states and an analogue of de Finetti’s theorem, Z. Wahrscheinlichkeitstheorie und Verw. Gebiete, 33(4) (1975/76) 343–351], we show that separability is equivalent to complete extendability for a state in a bipartite Hilbert space where at least one of which is of dimension greater than 2. This, in particular, extends the result of Fannes, Lewis, and Verbeure [Symmetric states of composite systems, Lett. Math. Phys. 15(3) (1988) 255–260] to the case of an infinite dimensional Hilbert space whose C* algebra of all bounded operators is not separable.

Metastable states of a composite system tunneling through repulsive barriers

We consider a method for solving the problem of quantum tunneling through repulsive potential barriers for a composite system consisting of several identical particles coupled via pair oscillator-type potentials in the oscillator symmetrized-coordinate representation. We confirm the efficiency of the proposed approach by calculating complex energy values and analyzing metastable states of composite systems of three, four, and five identical particles on a line, which leads to the effect of quantum transparency of the repulsive barriers.

Quantum correlations expressed as information and entropic inequalities for composite and noncomposite systems

For noncomposite systems in classical and quantum domains, we obtain new inequalities such as the subadditivity and strong subadditivity conditions for Shannon entropies and information determined by the probability distributions and for von Neumann entropies of quantum states determined by the density operators. We extend the relations of Shannon and Tsallis entropies to the entropies of conditional probability distributions known for composite systems to the case of noncomposite systems. We give a review of the approach to construct the tomographic-probability distributions for qudit systems and present the entropic and information inequalities for spin tomograms, as well as the subadditivity and strong subadditivity conditions for tomograms of the both noncomposite and composite system states.

Quantum entanglement in composite systems

We discuss a certain class of models of mesoscopic quantum phenomena that result from associating a particular type of Hamiltonian dynamics with the entangled states of composite systems. Using such models, we can concisely describe the phenomenology of a two-dimensional electron gas, in particular, the quantum Hall effect. We show how such models (if they are regarded as reflecting actual physical principles and not only the phenomenology) can be tested by a quantum teleportation-type experiment. The so-called mesoscopic models stipulate that the dynamics of a two-dimensional gas coupled to an ambient field is captured by a functional of the type Tr[Hρ] + βTr f(ρ), where ρ is the density operator and H is a single-particle Hamiltonian. We use the proposed approach to demonstrate that a suitable quantum teleportation experiment can provide information about the analytic function f. This leads us to view the composite system of an electron gas and an ambient field as a natural quantum computer.

On separable states for composite systems of distinguishable fermions

We study separable (i.e., classically correlated) states for composite systems of spinless fermions that are distinguishable. For a proper formulation of entanglement formation for such systems, the state decompositions for mixed states should respect the univalence superselection rule. Fermion hopping always induces non-separability, while states with bosonic hopping correlation may or may not be separable. Under the Jordan–Klein–Wigner transformation from a given bipartite fermion system into a tensor product one, any separable state for the former is also separable for the latter. There are, however, U(1)-gauge invariant states that are non-separable for the former but separable for the latter.

On Partially Entanglement Breaking Channels

Using well known duality between quantum maps and states of composite systems we introduce the notion of Schmidt number for a quantum channel. It enables one to define classes of quantum channels which partially break quantum entanglement. These classes generalize the well known class of entanglement breaking channels.

Statistical mechanics of colloids and Boltzmann’s definition of the entropy

The Boltzmann entropy as traditionally presented in statistical mechanics textbooks is only a special case and not Boltzmann's fundamental definition. The difference becomes important when the traditional expression for the entropy is applied to colloids, for which it makes incorrect predictions. Boltzmann's original definition of the entropy in terms of the probabilities of states of composite systems leads to consistent and correct statistical mechanics and thermodynamics.

On extremal quantum states of composite systems with fixed marginals

We study the convex set C(ρ1,ρ2) of all bipartite quantum states with fixed marginal states ρ1 and ρ2. The extremal states in this set have recently been characterized by Parthasarathy [Ann. Henri Poincaré (to appear), quant-ph/0307182]. Here we present an alternative necessary and sufficient condition for a state in C(ρ1,ρ2) to be extremal. Our approach is based on a canonical duality between bipartite states and a certain class of completely positive maps and has the advantage that it is easier to check and to construct explicit examples of extremal states. In dimension 2×2 we give a simple new proof for the fact that all extremal states in C(121,121) are precisely the projectors onto maximally entangled wave functions. We also prove that in higher dimension this does not hold and construct an explicit example of an extremal state in C(131,131) that is not maximally entangled. Generalizations of this result to higher dimensions are also discussed.

Violation of majorization relations in entangled states and its detection by means of generalized entropic forms

We examine the violation of the majorization relations between the eigenvalues of the full and reduced density operators of entangled states of composite systems and its detection using generalized entropic forms based on arbitrary concave functions. It is shown that the violation of these relations may not always be detected by the conditional von Neumann and Tsallis entropies (for any $q>0$). Families of smooth entropic forms which are always able to detect such violations are, however, provided. These features are then examined for particular sets of mixed states in a two-qudit system, which for $d\geq 3$ may exhibit different types of violation of the majorization relations. Comparison with the Peres criterion for separability is also shown.

On state-dependent implication in quantum-mechanical distant correlations

Let be an arbitrary given composite-system state (statistical operator). It is shown that same-subsystem events imply each other state-dependently according to if and only if they act equally in the range of the corresponding subsystem state (reduced statistical operator). Opposite-subsystem events imply each other in the same way if and only if they are twin events, i.e. . If is a pure state, it is shown that the anti-unitary correlation operator also plays a decisive role in the latter implication.

Automated state model generation algorithm for power circuits and systems

A new approach of automatically generating state-space models of power circuits and systems is presented. In this approach, the composite system state equations are established algorithmically given the standard node incidence matrix and elementary branch data (e.g. resistances, inductances, back emfs). The resulting state equations can be solved using a variety of numerical techniques or commercially available computer simulation programs. An example system consisting of a three-phase generator and rectifier load is used to illustrate this approach. Experimental verification is also provided.

Algorithms for Automated Protocol Verification

This paper studies the four basic types of algorithm that, over the last 10 years, have been developed for the automated verification of the logical consistency of data communication protocols. The algorithms are compared on memory usage, CPU time requirements, and the quality of the search for errors. It is shown that the best algorithm, according to above criteria, can be improved further in a significant way, by avoiding a known performance bottleneck. The algorithm derived in this manner works in a fixed-size memory arena (it will never run out of memory), it is up to 2 orders of magnitude faster than the previous methods, and it has superior coverage of the state space when analyzing large protocol systems. The algorithm is the first for which the search efficiency (the number of states analyzed per second) does not depend on the size of the state space: there is no time penalty for analyzing very large state spaces. The practicality of the new algorithm has been tested in the verification of portions of AT&T's 5ESS® switch. The models analyzed in these tests generated up to 250 million composite system states, that could be analyzed effectively in an hour's worth of CPU time on a large mainframe computer.

Solvation-induced charge separation in the excited state of composite systems with identical halves and intramolecular excimer formation by recombination: picosecond laser photolysis studies on 1,2-dianthrylethanes

Afin de determiner le mecanisme de formation de l'excimere intramoleculaire de [dianthryl-1,1']- et [dianthryl-9,9']-1,2 ethanes (DAE), on etudie leur photolyse sous faisceau laser dans differents solvants

Picosecond laser photolysis studies on dimer model systems in relation to photosynthetic charge separation processes

In relation to the photoinduced charge separation in the special pair of photosynthetic reaction center, solvation induced intramolecular electron transfer in the excited state of composite system with identical halves have been investigated with picosecond spectroscopy in the case of 1,2-dienthrylethanes. The energy gap dependences of charge separation and charge recombination in these systems are demonstrated and compared with those of hybrid dimer model of metal porphyrins, porphyrin-quinone systems and various aromatic donor-acceptor systems. The significance of these results in the understanding of efficient charge separation in biological reaction center is discussed.

Pre-equilibrium emission in neutron induced reactions on54,56Fe

The experimentally well known (n, p), (n, α) and (n, 2n) reaction excitation functions, from threshold to 20 MeV incident energy, and neutron and proton emission spectra at 14.8 MeV from54,56Fe targets are calculated in the frame of the Geometry-Dependent Hybrid pre-equilibrium emission model, including angular momentum and parity conservation, and the Hauser-Feshbach statistical model. Use of a consistent statistical model parameter set enables the validation of the pre-equilibrium emission model. Moreover, an enhanced pre-equilibrium emission from higher spin composite system states, associated with higher incoming orbital momenta, has been evidenced. Higher orbital momenta involved also in the emergent channels of the process are suggested by calculations of the residual nuclei level populations.