The laws of quantum mechanics, such as the unitarity of time evolution, ensure that the sequence of cause and effect remains consistent. In quantum theory, the state of a system evolves deterministically according to the Schrödinger equation, and this evolution preserves the temporal ordering of events.
The concept of causality is deeply ingrained in the mathematical formalism of quantum mechanics. The notion of cause and effect is preserved through the concept of operators and their commutation relations. Quantum mechanics enforces a consistent notion of time ordering through properties like the hermiticity of observables and the positivity of the inner product.
While quantum mechanics introduces non-classical phenomena such as superposition and entanglement, these do not fundamentally alter the causal structure of the theory. Entangled states, for instance, do not allow for the transmission of information or influence faster than the speed of light and thus respect the principle of causality.
Therefore, in quantum mechanics, the causal order between events remains fixed and is not subject to change.
