12,219 research outputs found
Quantum Nonlocality of N-qubit W states
An experimental setup for testing quantum nonlocality of N qubits is
proposed. This method is a generalization of the optical setup proposed by
Banaszek and Wodkiewicz [1]. The quantum nonlocality of N qubits can be
obtained through its violation of N-qubit Bell inequalities. The correlation
function measured in the experiment is described by the Wigner function. The
effect of inefficient detector is also considered.Comment: 5 pages and 2 figures, some errors are corrected in v
Continuous Multipartite Entangled State in Wigner Representation and the Violation of Zukowski-Brukner Inequality
We construct an explicit Wigner function for N-mode squeezed state. Based on
a previous observation that the Wigner function describes correlations in the
joint measurement of the phase-space displaced parity operator, we investigate
the non-locality of multipartite entangled state by the violation of
Zukowski-Brukner N-qubit Bell inequality. We find that quantum predictions for
such squeezed state violate these inequalities by an amount that grows with the
number N.Comment: 5 pages, rewritten version, accepted by Phys. Rev.
Violating Bell Inequalities Maximally for Two -Dimensional Systems
We investigate the maximal violation of Bell inequalities for two
-dimensional systems by using the method of Bell operator. The maximal
violation corresponds to the maximal eigenvalue of the Bell operator matrix.
The eigenvectors corresponding to these eigenvalues are described by asymmetric
entangled states. We estimate the maximum value of the eigenvalue for large
dimension. A family of elegant entangled states that violate
Bell inequality more strongly than the maximally entangled state but are
somewhat close to these eigenvectors is presented. These approximate states can
potentially be useful for quantum cryptography as well as many other important
fields of quantum information.Comment: 6 pages, 1 figure. Revised versio
Bell inequalities for three particles
We present tight Bell inequalities expressed by probabilities for three four-
and five-dimensional systems. The tight structure of Bell inequalities for
three -dimensional systems (qudits) is proposed. Some interesting Bell
inequalities of three qubits reduced from those of three qudits are also
studied.Comment: 8 pages, 3 figures. Accepted for publication in Phys. Rev.
- …