Fractionalization in the cuprates: Detecting the topological order

The precise theoretical characterization of a fractionalized phase in spatial dimensions higher than one is through the concept of ``topological order''. We describe a physical effect that is a robust and direct consequence of this hidden order that should enable a precise experimental characterization of fractionalized phases. In particular, we propose specific ``smoking-gun'' experiments to unambiguously settle the issue of electron fractionalization in the underdoped cuprates.