Dual channel NOR and XNOR logic realized by temporally graded photonic time crystals for information encryption

Photonic time crystals (PTCs) provide a temporal degree of freedom for manipulating electromagnetic waves and offer a promising platform for optical information processing. A scheme for dual channel Boolean logic and information encryption based on a temporally graded PTC is proposed. Binary inputs are encoded by assigning different temporal gradient parameters to the graded transition layers, and the output states are decoded from the features of reflection peaks within selected spectral windows. The same temporal configuration supports two interleaved spectral logic channel families. In the considered spectral range, the reflection peaks at k/k0 = 4m − 2 correspond to NOR responses, whereas those at k/k0 = 4m correspond to XNOR responses, with m denoting a positive integer. This spectral order dependence enables the Boolean operation to be selected through the reflection channel rather than by redesigning the temporal structure. As an application demonstration, two external binary key matrices are processed through the NOR and XNOR spectral channels to generate an effective key for color image encryption and decryption. The dual key design enlarges the key combination space and makes successful decryption dependent on both the external keys and the assigned spectral logic channels. These results suggest that temporally graded PTCs can integrate temporal wave manipulation, spectral Boolean logic, and optical information encoding within a unified time-varying platform.