Classical correlations and entanglement

Martin Plesch, Vladimír Bužek

Bipartite correlations in multiqubit systems cannot be shared freely. The presence of entanglement or classical correlation on certain pairs of qubits may imply correlations on other pairs. We present a method of characterization of bipartite correlations in multiqubit systems using a concept of entangled graphs which has been introduced in our earlier work @M. Plesch and V. Bužek, Phys. Rev. A 67, 012322 ~2003!#. In entangled graphs, each qubit is represented by a vertex while the entanglement and classical correlations are represented by two types of edges. We prove by construction that any entangled graph with classical correlations can be represented by a mixed state of N qubits. However, not all entangled graphs with classical correlations can be represented by a pure state.

Shunlong Luo, You-feng Luo

Martin Plesch, Vladimír Bužek

Bipartite correlations in multiqubit systems cannot be shared freely. The presence of entanglement or classical correlation on certain pairs of qubits may imply correlations on other pairs. We present a method of characterization of bipartite correlations in multiqubit systems using a concept of entangled graphs which has been introduced in our earlier work [M. Plesch and V. Bu\ifmmode \check{z}\else \v{z}\fi{}ek, Phys. Rev. A 67, 012322 (2003)]. In entangled graphs, each qubit is represented by a vertex while the entanglement and classical correlations are represented by two types of edges. We prove by construction that any entangled graph with classical correlations can be represented by a mixed state of N qubits. However, not all entangled graphs with classical correlations can be represented by a pure state.

Bei Zeng, Xie Chen, D. L. Zhou +1 more

Ping‐Xing Chen

The correlated imaging is an interesting topic.Whether second correlated imaging is a pure quantum effect or classical effect is still implicit.One phenomenon of quantum theory or classical theory,which is an interesting topic.This paper analyses three correlated imaging schemes together.The first two schemes can be achieved by two-photon which is classical correlated or quantum entangled and the third one can only be achieved by entangled two-photon.Through the comparison of these schemes,we find that entangled two-photon which can be used in all the three schemes is correlated both in position and momentum.However,the classical correlated two-photon only correlate in position or momentum,and only can be used in one scheme.