Nat. Commun. 9, 1259 (2018)

Nuclear non-proliferation treaties are vitally important for global security, but they are difficult to enforce because nations want to be secretive about the details of their weapons technology, even during inspections. To combat this, Jake Hecla and Areg Danagoulian propose a zero-knowledge method for examining the fissile plutonium ‘pit’ in a warhead, to verify its geometry and isotopic composition.

The isotopes of plutonium have quite different interaction cross-sections with neutrons in the 1-eV to 10-eV energy range, but doing a simple measurement of the absorption spectrum of the pit would reveal crucial information about it. The authors’ proposal is to introduce a specially designed reciprocal mask so that the neutrons traverse both the pit and the mask. The mask is templated in such a way that the absorption spectrum verifies the construction of the pit but does not reveal detailed information about its design. Crucially, detailed calculations show that this method is resistant to various types of hoaxes.