  Recent work has shown that collective single photon emission from an ensemble
of resonate two-level atoms, i.e. single photon superradiance, is a rich field
of study. The present paper addresses the flip side of superradiance, i.e.
subradiance. Single photon subradiant states are potentially stable against
collective spontaneous emission and can have ultrafast readout. In particular
it is shown how many atom collective effects provide a new way to control
spontaneous emission by preparing and switching between subradiant and
superradiant states.
