  The speed of computations is investigated by means of the orthogonality speed
for a charged qubit interacting with a single cavity field prepared initially
in a Fock state or Binomial state. We observe that the rate of the
computational speed is related to the number of photons inside the cavity.
Moreover, we show that the qubit-field coupling plays an opposite role, where
the speed of computations is decreased as the coupling is increased. We suggest
using the number of photons in the field as a control parameter to improve the
speed of computations.
