New observables with which we can study the two-nucleon weak interactions at low energies are considered. In the breakup of the deuteron by photons, polarization of outgoing neutrons can depend on the parity-violating component of two-nucleon interactions. We express the parity-violating polarization in general forms, and perform numerical calculations with a pionless effective field theory. The theory has unknown parity-violating low energy constants, and the results are expressed in linear

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... bination of them. We discuss the results and their implication to the understanding of the hadronic weak interactions.