| Quantum-secure optical readout of a physical key. (a) Setup: a spatial light modulator (SLM1) creates the challenge by phase shaping a few-photon wavefront. In the experiment a 50×50 binary phase pattern is used with 0- and π-phase delays. The challenge is sent to the ZnO key (scale bar is 4μm) by a microscope objective.
The response is coupled out by a polarizing beam splitter. The response is transformed back by SLM2 and then focused onto the analyzer plane. (b) Only if the key is the true unique key, the response has a bright spot in the center, holding ≈60% of the power in the image and allowing that fraction to pass a pinhole and land on a detector where photodetection clicks authenticate the key. (c) In case of a false key, the response in the analyzer plane is a random speckle pattern. |
