Entanglement purification protocols (EPPs) and quantum error-correcting codes (QECCs)
provide two ways of protecting quantum states from interaction with the environment. In an …

We present a measure of entanglement that can be computed effectively for any mixed state
of an arbitrary bipartite system. We show that it does not increase under local manipulations …

Secret sharing is a procedure for splitting a message into several parts so that no subset of
parts is sufficient to read the message, but the entire set is. We show how this procedure can …

If two separated observers are supplied with entanglement, in the form of n pairs of particles
in identical partly entangled pure states, one member of each pair being given to each …

We prove a theorem on direct relation between the optimal fidelity f max of teleportation and
the maximal singlet fraction F max attainable by means of trace-preserving local quantum …

We show how a quantum secret sharing protocol, similar to that of Hillery, Buzek, and
Berthiaume (Los Alamos e-print archive quant-ph/9806063), can be implemented using two …

We analyze the problem of distillation of entanglement of mixed states in higher-dimensional
compound systems. Employing the positive maps method [M. Horodecki et al., Phys. Lett. A …

A protocol for quantum secure direct communication with quantum superdense coding is
proposed. It combines the ideas of block transmission, the **-pong quantum secure direct …

We study the use of entanglement purification for quantum communication over long
distances. For distances much longer than the coherence length of a corresponding noisy …

Using the process of spontaneous parametric down-conversion in a two-crystal geometry,
we have generated a source of polarization-entangled photon pairs that is more than ten …