Synthetic magnetic encryption in a two-level photonic system

We demonstrate both theoretically and experimentally an optical encryption technique that uniquely utilizes a fundamental concept of synthetic magnetic field, a gauge field capable of controlling light propagation phenomena. We synthesize such a magnetic field for the optical information encryption, by using the spin-1/2 formulism, which is realized in an electrically engineered photonic crystal. In the presence of the synthetic magnetic field, the differently pseudo spins become effectively coupled, allowing transfer of spatial structures of the 'magnetic' field to the precessions of photonic pseudo spins. Based on this synthetic framework, we realize spatially invariant and linearly varying synthetic magnetic fields, successfully realizing the synthetic magnetic encryptions. Our result is shown to be extended to encrypt complex image information, highlighting the potential of the synthetic magnetic field in the optical information storage and processing. Unlike previous optical encryption methods, which rely on manipulations of different optical parameters (amplitude, phase, polarization, coherence, wavelength, etc.), our technique provides a different dimension (synthetic magnetic field) for the optical encryption.