Stochastic resonance shows that under some circumstances noise can enhance
the response of a system to a periodic force. While this effect has been ex
tensively investigated theoretically and demonstrated experimentally in cla
ssical systems, there is complete lack of experimental evidence within the
purely quantum-mechanical domain. Here we demonstrate that stochastic reson
ance can be exhibited in a single ion and would be experimentally observabl
e using well mastered experimental techniques. We discuss the use of this s
cheme for the detection of the frequency difference of two lasers to demons
trate that stochastic resonance may have applications in precision measurem
ents at the quantum limit.