Causality in Quantum Entangled States

The application of a new method of the quantum cause-and-effect analysis, where causality is determined without reference to a delay, for entangled states is considered. This helps to understand the Cramer's weak-causality principle allowing for time reverse in entangled states. It is found that the finite causality can exist only in mixed asymmetric entangled states. The causality parameters are computed for a series of three-qubit entangled states. Results are compared with measures of mixedness and entanglement. For the simplest cases, the formal measure of causality is not inconsistent with intuitive representations. However when a situation is somewhat complicated, the intuition may bring to an incorrect result, whereas the cause-and-effect analysis demonstrates a nontrivial role of the state asymmetry in transfer of quantum information.