Quantum entanglement and fixed-point bifurcations

How does the classical phase space structure for a composite system relate to the entanglement characteristics of the corresponding quantum system? We demonstrate how the entanglement in nonlinear bipartite systems can be associated with a fixed point bifurcation in the classical dynamics. Using the example of coupled giant spins we show that when a fixed point undergoes a supercritical pitchfork bifurcation, the corresponding quantum state - the ground state - achieves its maximum amount of entanglement near the critical point. We conjecture that this will be a generic feature of systems whose classical limit exhibits such a bifurcation.Comment: v2: Structure of the paper changed for clarity, reduced length, now 9 pages with 6 figure

Trends in Programming Languages for Neuroscience Simulations

Neuroscience simulators allow scientists to express models in terms of biological concepts, without having to concern themselves with low-level computational details of their implementation. The expressiveness, power and ease-of-use of the simulator interface is critical in efficiently and accurately translating ideas into a working simulation. We review long-term trends in the development of programmable simulator interfaces, and examine the benefits of moving from proprietary, domain-specific languages to modern dynamic general-purpose languages, in particular Python, which provide neuroscientists with an interactive and expressive simulation development environment and easy access to state-of-the-art general-purpose tools for scientific computing

NEURON and Python

The NEURON simulation program now allows Python to be used, alone or in combination with NEURON's traditional Hoc interpreter. Adding Python to NEURON has the immediate benefit of making available a very extensive suite of analysis tools written for engineering and science. It also catalyzes NEURON software development by offering users a modern programming tool that is recognized for its flexibility and power to create and maintain complex programs. At the same time, nothing is lost because all existing models written in Hoc, including graphical user interface tools, continue to work without change and are also available within the Python context. An example of the benefits of Python availability is the use of the xml module in implementing NEURON's Import3D and CellBuild tools to read MorphML and NeuroML model specifications

Doing Deals in Japan: An Analysis of Recent Trends & Developments for the U.S. Practitioner

This article examines the process which is currently being played out in Japan by: (i) analyzing the recent changes in Japanese law of relevance to M&A deals, (ii) discussing some recent contested deals in Japan that may shed some light on current market practices, and (iii) providing an overview of the key issues that a U.S. practitioner will likely face when working on a Japanese deal…A good starting point in better understanding the remarkable changes in the Japanese M&A markets is to review the recent amendments to Japanese law, certain policy initiatives by the functional regulators, and other guidelines issued by Japanese government agencies… In concert with the changes in Japanese law, we have seen an increase in the number of contested deals in Japan in recent years…[T]he challenge for the U.S. practitioner is to boil down the complexity of Japanese M&A to a list of key issues that should be reviewed in any transaction which involves Japanese entities…[W]e have set forth some of the main issues under Japanese law and U.S. securities laws that have often come into play in Japanese deals…The current Japanese M&A market presents opportunities for U.S. companies and their advisors that are arguably the most promising in recent history…[G]iven the challenges posed by the opportunities in the Japanese M&A market, the importance of well informed and considered decision-making will be essential in order to ensure that U.S. companies compete and succeed in doing Japanese deals

Quantum Entanglement and Fixed-Point Bifurcations

How do the classical dynamics of a composite system relate to the entanglement characteristics of the corresponding quantum system? We show that entanglement in nonlinear bipartite systems can be associated with a fixed point bifurcation in the classical description. In a non dissipative system a fixed point corresponds to a quantum stationary state, usually a ground state. Using the example of coupled giant spins we show that, when the fixed point undergoes a supercritical pitchfork bifurcation, the corresponding quantum state achieves a maximum amount of entanglement. By way of contrast, we consider a molecular BEC system that experiences a different kind of bifurcation and does not exhibit a peak in the entanglement corresponding to the bifurcation parameter

Entanglement Sharing and Decoherence in the Spin-Bath

The monogamous nature of entanglement has been illustrated by the derivation of entanglement sharing inequalities - bounds on the amount of entanglement that can be shared amongst the various parts of a multipartite system. Motivated by recent studies of decoherence, we demonstrate an interesting manifestation of this phenomena that arises in system-environment models where there exists interactions between the modes or subsystems of the environment. We investigate this phenomena in the spin-bath environment, constructing an entanglement sharing inequality bounding the entanglement between a central spin and the environment in terms of the pairwise entanglement between individual bath spins. The relation of this result to decoherence will be illustrated using simplified system-bath models of decoherence.Comment: 5 pages, 1 figure v2: 6 pages 2 figures, additional example and reference