  Given a black-box representing an unknown Boolean function $f$ of $n$
variables, in this paper we propose a fast quantum algorithm to test whether or
not a certain variable in the function $f$ is a junta variable. The proposed
algorithm creates entanglement between the variable under test and an auxiliary
qubit, where the entanglement is measured using concurrence measure to decide
if the variable is junta. The paper shows applications to the proposed
algorithm in learning and categorization of Boolean functions.
