An all-photonic molecular keypad lock.

Off and on: A molecular triad, consisting of a porphyrin linked to two different, independently addressable photochromic moieties, functions as a molecular keypad lock with all-photonic inputs and output. The porphyrin correlates the responses of the two inputs to light of different wavelengths and provides an appropriate output as fluorescence, which results only when one of eight possible input combinations has been applied (see figure).