1.   Reactions with very fast rates often involve particles known as free radicals.

2.   Both concepts rely heavily on the ability of light to carry so-called quantum information, involving particles that can exist in many places or states at once.

3.   Scientists at the University of Washington in Seattle and Johns Hopkins University are proposing solutions that involve particles called neutrinos and baryons.

4.   The advantage of the model is that it involves light particles, called pions, that actually exist, but are invoked here in a different context.