Confirming the pedigree of uranium cubes from Nazi Germany's failed nuclear program

During World War II, Nazi Germany and the U.S. were racing to develop nuclear technology. Before Germany could succeed, Allied forces disrupted the program and confiscated some of the cubes of uranium at the heart of it. The ultimate fate of most of that uranium is unknown, but a few cubes thought to be associated with the program are in the U.S. and Europe. Today, scientists report initial results from new methods being developed to confirm their provenance. The techniques might also help with investigations into illicit trafficking of nuclear material.