  We calculate the zeros of an exponential polynomial of three variables by a
classical algorithm and quantum algorithms which are based on the method of van
Dam and Shparlinski, they treated the case of two variables, and compare with
the time complexity of those cases. Further we compare the case of van Dam and
Shparlinski with our case by considering the ratio (classical/quantum) of the
time complexity. Then we can observe the ratio decreases.
