2,258 research outputs found
Witnessed Entanglement
We present a new measure of entanglement for mixed states. It can be
approximately computable for every state and can be used to quantify all
different types of multipartite entanglement. We show that it satisfies the
usual properties of a good entanglement quantifier and derive relations between
it and other entanglement measures.Comment: Revised version. 7 pages and one figur
Wanted Dead or Alive? The Relative Value of Reef Sharks as a Fishery and an Ecotourism Asset in Palau
Over the last 20 years, ecotourism to view and interact with marine megafauna has become increasingly popular (Higham and Lück 2008). Examples of this type of tourism include turtle and whale watching, snorkelling with seals and shark diving (Jacobson and Robles 1992; Anderson and Ahmed 1993; Orams 2002; Kirkwood et al. 2003; Dearden et al. 2008; Dicken and Hosking 2009). The occurrence of many aggregations of megafauna along the coasts of regional areas remote from centres of population means that such tourism also provides significant flow-on effects and diversification to local economies where few alternative sources of income exist (Milne 1990; Garrod and Wilson 2004). Importantly, the development of a well-managed ecotourism industry based on megafauna provides the opportunity for local people to utilise natural resources in a sustainable manner over the long-term (Mau 2008). The economic value of tourism based on marine megafauna is enormous. In 2008, a study of whale watching estimated that this form of tourism was available in 119 countries, involved approximately 13 million participants and generated an income to operators and supporting businesses (hotels, restaurants and souvenirs) of over US2.5 billion (Cisneros-Montemayor et al. 2010). The development of whale watching has been paralleled by growth in tourism based on other types of marine megafauna. In particular, tourism to observe sharks and rays has become increasingly common. At the forefront of this relatively new market are industries that focus on whale sharks (Rhincodon typus) with estimates calculated in 2004 suggesting that these generated more than US$47.5 million worldwide, providing important revenues to developing countries such as Ecuador, Thailand and Mozambique (Graham 2004). Diving with other species of sharks has followed a similar trend of growing popularity. In 2005, it was estimated that approximately 500,000 divers were engaged in shark-diving activities worldwide (Topelko and Dearden 2005). An increasing range of opportunities for this type of tourism are available, including cage diving, shark feeding and drift diving with reef and oceanic sharks. Shark-diving tourism can be found in more than 40 countries (Carwardine and Watterson 2002), with new destinations and target species being established rapidly, due to the increasing recognition of the economic potential of this activity (Dicken and Hosking 2009; De la Cruz Modino et al. 2010)
The Socio-Economic Value of the Shark-Diving Industry in Fiji
Based on a survey of divers, dive operators, resort managers, estimates business revenues from shark diving and related expenditures by area; tax revenues; and economic benefit to local communities
Study of the Distillability of Werner States Using Entanglement Witnesses and Robust Semidefinite Programs
We use Robust Semidefinite Programs and Entanglement Witnesses to study the
distillability of Werner states. We perform exact numerical calculations which
show 2-undistillability in a region of the state space which was previously
conjectured to be undistillable. We also introduce bases which yield
interesting expressions for the {\em distillability witnesses} and for a tensor
product of Werner states with arbitrary number of copies.Comment: 16 pages, 2 figure
Viable entanglement detection of unknown mixed states in low dimensions
We explore procedures to detect entanglement of unknown mixed states, which
can be experimentally viable. The heart of the method is a hierarchy of simple
feasibility problems, which provides sufficient conditions to entanglement. Our
numerical investigations indicate that the entanglement is detected with a cost
which is much lower than full state tomography. The procedure is applicable to
both free and bound entanglement, and involves only single copy measurements.Comment: 8 pages, 9 figures, 4 table
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