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Aditi Sen De

Publications and source records attributed to Aditi Sen De.

259 records · Page 15Linked to original sources
arXiv2003

Can there be quantum correlations in a mixture of two separable states?

We use a recently proposed measure of quantum correlations (work deficit), to measure the strength of the nonlocality of an equal mixture of two bipartite, orthogonal, but locally indistinguishable separable states. This gives supporting evidence of nonzero value for a separable state, for this measure of nonlocality. We also show that this measure of quantum correlations places a different order on the set of states, than the good asymptotic measures of entanglement. And that such a different order imposed on two states by the work deficit and any entanglement measure, cannot be explained by mixedness alone.

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arXiv2003

Information as a resource in distributed quantum systems

A new paradigm for distributed quantum systems where information is a valuable resource is developed. After finding a unique measure for information, we construct a scheme for it's manipulation in analogy with entanglement theory. In this scheme instead of maximally entangled states, two parties distill local states. We show that, surprisingly, the main tools of entanglement theory are general enough to work in this opposite scheme. Up to plausible assumptions, we show that the amount of information that must be lost during the protocol of concentration of local information can be expressed as the relative entropy distance from some special set of states.

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arXiv2002

Local indistinguishability and LOCC monotones

We provide a method for checking indistinguishability of a set of multipartite orthogonal states by local operations and classical communication (LOCC). It bases on the principle of nonincreasing of entanglement under LOCC. This method originates from the one introduced by Ghosh \emph{et al.} (Phys. Rev. Lett. \textbf{87}, 5807 (2001) (quant-ph/0106148)), though we deal with {\emph pure} states. In the bipartite case, our method is operational, although we do not know whether it can always detect local indistinguishability. We apply our method to show that an arbitrary complete multipartite orthogonal basis is indistinguishable if it contains at least one entangled state. We also show that probabilistic distinguishing is possible for full basis if and only if all vectors are product. We employ our method to prove local indistinguishability in a very interesting example akin to "nonlocality without entanglement".

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arXiv2001

On local indistinguishability of orthogonal pure states by using a bound on distillable entanglement

We show that the four states a|00>+b|11>, b^*|00>-a^*|11>, c|01>+d|10> and d^*|01>-c^*|10> cannot be discriminated with certainty if only local operations and classical communication (LOCC) are allowed and if only a single copy is provided, except in the case when they are simply |00>, |11>, |01> and |10> (in which case they are trivially distinguishable with LOCC). We go on to show that there exists a continuous range of values of a, b, c and d such that even three states among the above four are not locally distinguishable, if only a single copy is provided. The proof follows from the fact that logarithmic negativity is an upper bound of distillable entanglement.

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arXiv2001

Distinguishability of the Bell states

More than two multipartite orthogonal states cannot always be discriminated (with certainty) if only local operations and classical communication (LOCC) are allowed. Using an existing inequality among the measures of entanglement, we show that any three Bell states cannot be discriminated by LOCC. Exploiting the inequality, we calculate the distillable entanglement of a certain class of (4\otimes 4) mixed states.

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arXiv2001

Mixedness in Bell-violation vs. Entanglement of Formation

Recently Munro, Nemoto and White (The Bell Inequality: A measure of Entanglement?, quant-ph/0102119) tried to indicate that the reason behind a state rho having higher amount of entanglement (as quantified by the entanglement of formation) than a state eta, but producing the same amount of Bell-violation, is due to the fact that the amount of mixedness (as quantified by the linearised entropy) in rho is higher than that in eta. We counter their argument with examples. We extend these considerations to the von Neumann entropy. Our results suggest that the reason as to why equal amount of Bell-violation requires different amounts of entanglement cannot, at least, be explained by mixedness alone.

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