72 research outputs found
Estimation of Entanglement Negativity of a Two-Qubit Quantum System With Two Measurements
Numerous work had been done to quantify the entanglement of a two-qubit
quantum state, but it can be seen that previous works were based on joint
measurements on two copies or more than two copies of a quantum state under
consideration. In this work, we show that a single copy and two measurements
are enough to estimate the entanglement quantifier like entanglement negativity
and concurrence. To achieve our aim, we establish a relationship between the
entanglement negativity and the minimum eigenvalue of structural physical
approximation of partial transpose of an arbitrary two-qubit state. The derived
relation make possible to estimate entanglement negativity experimentally by
Hong-Ou-Mandel interferometry with only two detectors. Also, we derive the
upper bound of the concurrence of an arbitrary two-qubit state and have shown
that the upper bound can be realized in experiment. We will further show that
the concurrence of (i) an arbitrary pure two-qubit states and (ii) a particular
class of mixed states, namely, rank-2 quasi-distillable mixed states, can be
exactly estimated with two measurements.Comment: 6 pages, 2 figures, Published versio
Entanglement and Teleportation in Bipartite System
We present a mathematical formulation of old teleportation protocol (original
teleportation protocol introduced by Bennett et.al.) for mixed states and study
in detail the role of mixedness of the two qubit quantum channel in a
teleportation protocol. We show that maximally entangled mixed state described
by the density matrix of rank-4 will be useful as a two qubit teleportation
channel to teleport a single qubit mixed state when the teleportation channel
parameter p1 greater than 0.5. Also we discuss the case when p1 less than equal
to 0.5.Comment: 16 pages and 5 figures. Accepted in IJQ
- …