One photon reveals both absorption and phase — simultaneously?

Entangled photon pairs let you image a sample in two complementary ways — measuring light absorption or phase shifts — from one acquisition, just by changing how you measure the photon that never touched the sample. The trick is quantum erasure: retrospectively 'erasing' or 'restoring' which-path information on a remote ancilla photon sorts the same dataset into two different images. The framework includes rigorous Fisher information bounds showing this matches the statistical efficiency of simply splitting acquisition time between the two modes.