Quantum entanglement is considered to be a central resource of quantum information processing: entanglement is a key ingredient in quantum teleportation [1], and is used to perform conditional two-qubit operations, which are primordial for running a quantum algorithm [2]. There is a large body of literature on the abstract, rather mathematical theory of entanglement [3], of pure as well as of m...

Entanglement distribution between distant parties is an essential component to most quantum communication protocols. Unfortunately, decoherence effects such as phase noise in optical fibres are known to demolish entanglement. Iterative (multistep) entanglement distillation protocols have long been proposed to overcome decoherence, but their probabilistic nature makes them inefficient since the ...

Analyzing the properties of entanglement in many-particle spin-1/2 systems is generally difficult because the system’s Hilbert space grows exponentially with the number of constituent particles, N. Fortunately, it is still possible to investigate a many-particle entanglement when the state of the system possesses sufficient symmetry. In this paper, we present a practical method for efficiently ...

In this paper we provide an operational method to detect multipartite entanglement in ensemble-based quantum computing. This method is based on the concept of entanglement witness. We decompose the entanglement witness for each class of multipartite entanglement into nonlocal operations in addition to local measurements. Individual single qubit measurements are performed simultaneously, hence c...

We examine the modal, spectral, and polarization entanglement properties of photon pairs generated in a nonlinear periodically poled two-mode waveguide one-dimensional planar or two-dimensional circular via nondegenerate spontaneous parametric down-conversion. Any of the possible degrees of freedom—mode number, frequency, or polarization—can be used to distinguish the down-converted photons whi...

Entanglement bits or “ebits” have been proposed as a quantitative measure of a fundamental resource in quantum information processing. For such an interpretation to be valid, it is important to show that the same number of ebits in different forms or concentrations are inter-convertible in the asymptotic limit. Here we draw attention to a very important but hitherto unnoticed aspect of entangle...

We present a family of tripartite entangled states that, in an asymptotical sense, can be reversibly converted into Einstein-Podolsky-Rosen (EPR) states, shared by parties B and C, and tripartite Greenberger-Horne-Zeilinger (GHZ) states. Thus we show that a bipartite and a genuine tripartite entanglement can be reversibly combined in a tripartite state. For such states the corresponding fractio...

We derive experimentally measurable lower bounds for the two-site entanglement of the spindegrees of freedom of many-body systems with local particle-number fluctuations. Our method aims at enabling the spatially resolved detection of spin-entanglement in Hubbard systems using highresolution imaging in optical lattices. A possible application is the observation of entanglement generation and sp...

We investigate the generation of multipartite entangled state in a system of N quantum dots embedded in a microcavity and examine the emergence of genuine multipartite entanglement by three different characterizations of entanglement. At certain times of dynamical evolution one can generate multipartite entangled coherent exciton states or multiqubit W states by initially preparing the cavity f...

Entanglement bits or " ebits " have been proposed as a quantitative measure of a fundamental resource in quantum information processing. For such an interpretation to be valid, it is important to show that the same number of ebits in different forms or concentrations are inter-convertible in the asymp-totic limit. Here we draw attention to a very important but hitherto unnoticed aspect of entan...