# Quantum Entanglement and Causality [duplicate]

How does Quantum Entanglement not violate the principle of relativity?

Alice and Bob are working on an entangled system of electrons which is spaced long apart. Now if Alice measures one electron to be up in the $z$ axis,she is actually orienting the spin of the electron in that axis. If the system under consideration is a singlet state, then the other electron will be oriented in the negative $z$ axis. If initially, Bob subjected the electron to a magnetic field along the positive $z$ axis, the electron would emit a photon or take up some energy to change its orientation thereby we have energy interactions taking place faster than the speed of light.

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## marked as duplicate by Emilio Pisanty, Qmechanic♦Sep 8 '13 at 17:00

This question was marked as an exact duplicate of an existing question.

Once extra interactions take place the entanglement breaks. The two electrons become uncorrelated. – anna v Sep 8 '13 at 14:38