  A tunable optical multistability scheme based on a single cavity mode coupled
with two separate atomic transitions in an atom-cavity system is proposed and
demonstrated. Under the collective strong coupling condition, multiple
polariton eigenstates of the atom-cavity system are produced. The threshold and
optical multistability curve can be tuned freely by system parameters in a
broadband range. Moreover, a certain bistability region of the system is split
to two bistability regions due to destructive quantum interference induced by
an extra weak control field. Compared to traditional optical multistabilities
created by two or more light fields, the proposed optical multistability scheme
has compactness and is easy to be miniaturized. The proposed scheme is useful
for manufacturing integrated application of multi-state all-optical logic
devices and constructing basic elements of all-optical communication networks.
