Efficient bipartite quantum state purification in arbitrary dimensional Hilbert spaces

A new purification scheme is proposed which applies to arbitrary dimensional bipartite quantum systems. It is based on the repeated application of a special class of nonlinear quantum maps and a single, local unitary operation. This special class of nonlinear quantum maps is generated in a natural way by a hermitian generalized XOR-gate. The proposed purification scheme offers two major advantages, namely it does not require local depolarization operations at each step of the purification procedure and it purifies more efficiently than other know purification schemes.Comment: This manuscript is based on results of our previous manuscript 'Generalized quantum XOR-gate for quantum teleportation and state purification in arbitrary dimensional Hilbert spaces

Purification of genuine multipartite entanglement

In tasks, where multipartite entanglement plays a central role, state purification is, due to inevitable noise, a crucial part of the procedure. We consider a scenario exploiting the multipartite entanglement in a straightforward multipartite purification algorithm and compare it to bipartite purification procedures combined with state teleportation. While complete purification requires an infinite amount of input states in both cases, we show that for an imperfect output fidelity the multipartite procedure exhibits a major advantage in terms of input states used.Comment: 5 pages, 2 figure

Extraction and purification of exopolysaccharides from exhausted Arthrospira platensis (Spirulina) culture systems

Microalgal endo and exopolysaccharides (EPS) are attracting increasing interest for their potential applications in the food, cosmetic and pharmaceutical industries. The standard applications of microbial EPS are as food coatings, emulsifying and gelling agents, flocculants, hydrating agents etc. They present unique biochemical properties that make them interesting from the biotechnological point of view. Their physical-chemical properties are interesting for biomedical applications, since polysaccharides have been demonstrated to possess inhibitory properties against various types of viruses, bacteria and tumors. The purpose of this work is to upgrade the exhausted culture media resulting from the cultivation of the cyanobacterium Arthrospira platensis (Spirulina), in order to extract the exopolysaccharides excreted by the cyanobacterium and test their exploitation potential in a cosmetic context (a body cream). The study results include: defining the composition and the productivity of EPS by the Spirulina culture, developing a suitable application method for the DPPH assay in lipophilic matrices, and evaluation of the antioxidant action of these polymers in the cosmetic field

Multiple copy distillation and purification of phase diffused squeezed states

We provide a detailed theoretical analysis of multiple copy purification and distillation protocols for phase diffused squeezed states of light. The standard iterative distillation protocol is generalized to a collective purification of an arbitrary number of N copies. We also derive a semi-analytical expression for the asymptotic limit of the iterative distillation and purification protocol and discuss its properties.Comment: 11 pages, 13 figure

Multiparticle entanglement purification for two-colorable graph states

We investigate multiparticle entanglement purification schemes which allow one to purify all two colorable graph states, a class of states which includes e.g. cluster states, GHZ states and codewords of various error correction codes. The schemes include both recurrence protocols and hashing protocols. We analyze these schemes under realistic conditions and observe for a generic error model that the threshold value for imperfect local operations depends on the structure of the corresponding interaction graph, but is otherwise independent of the number of parties. The qualitative behavior can be understood from an analytically solvable model which deals only with a restricted class of errors. We compare direct multiparticle entanglement purification protocols with schemes based on bipartite entanglement purification and show that the direct multiparticle entanglement purification is more efficient and the achievable fidelity of the purified states is larger. We also show that the purification protocol allows one to produce private entanglement, an important aspect when using the produced entangled states for secure applications. Finally we discuss an experimental realization of a multiparty purification protocol in optical lattices which is issued to improve the fidelity of cluster states created in such systems.Comment: 22 pages, 8 figures; replaced with published versio

The entanglement of purification

We introduce a measure of both quantum as well as classical correlations in a quantum state, the entanglement of purification. We show that the (regularized) entanglement of purification is equal to the entanglement cost of creating a state $\rho$ asymptotically from maximally entangled states, with negligible communication. We prove that the classical mutual information and the quantum mutual information divided by two are lower bounds for the regularized entanglement of purification. We present numerical results of the entanglement of purification for Werner states in ${\cal H}_2 \otimes {\cal H}_2$.Comment: 12 pages RevTex, 1 figure, to appear in JMP special issue on quantum information. v3 contains additional references, motivation, and a small change in the figur