Physical matching has long been a cornerstone of secure authentication systems, as exemplified by the Tiger Amulet in ancient military contexts. However, traditional methods are constrained by reliance on tangible objects and the necessity of “localized” matching within physical space. Ghost imaging (GI), which utilizes correlated light beams for indirect object reconstruction, presents a promising alternative for nonlocalized verification. Despite significant progress, second-order correlation-based GI techniques are limited to assessing object similarity and cannot capture the complementary relationship between objects that together form a complete entity. In this study, we introduce a third-order thermal GI approach for complementary object matching. By employing three correlated beams, this technique enables the secure authentication of objects that form a unified whole. When complementary objects match the reference object, a distinct correlation peak is observed, whereas a mismatch results in noise. This optical authentication mechanism holds considerable potential for enhancing security in communication and encryption systems.

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• Ghost imaging
• Imaging & optical processing
• Spatial light modulators
• Optical computing