  By sending a classical two-level system, one can transfer information about
only \emph{two} distinguishable outcomes. Here we show that in quantum
mechanics, using both the spin and path degrees of freedom of a spin-1/2
particle, and a Mach-Zehnder type interferometric arrangement with two suitable
Stern-Gerlach detectors, it is possible to transfer information about
\emph{four} distinguishable outcomes. This procedure does \emph{not} require
using quantum entanglement as a resource as in the well-known protocol of dense
coding, but instead hinges entirely on the quantum superposition principle. We
also study probabilistic dense coding using our set-up and show that the dense
coding scheme using quantum superposition cannot be optimized any further by
extending the interferometric arrangement with more beam splitters.
