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Two gamma ray photons are entangled and travel through space. The first gamma photon interacts with a low frequency photon and creates an electron positron pair. What happens to the other gamma photon, does it's motion (position, momentum, spin etc) change as well thus creating another electron positron pair?

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Ignoring the fact that this is a reaction with very low probability and the difficulty of detecting such an interaction the answer is : no, nothing happens to the quantum mechanical status of the other gamma.

If by some ingenious method one managed to determine the spins in the pair produced, still the spin of the parent gamma would be unknown, since the low energy photon also has an unknown spin direction. The only entanglement the two gammas can have are with the spin properties, and this information is lost with the interaction you propose.

Entanglement in energy could happen in known cascade decays of two gammas from a nucleus. If one detects two coincident gammas and measures the energy of one of them, the energy of the other would be known. thats all.

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