  We explore NOT gate response in a mesoscopic ring threaded by a magnetic flux
$\phi$. The ring is attached symmetrically to two semi-infinite one-dimensional
metallic electrodes and a gate voltage, viz, $V_a$, is applied in one arm of
the ring which is treated as the input of the NOT gate. The calculations are
based on the tight-binding model and the Green's function method, which
numerically compute the conductance-energy and current-voltage characteristics
as functions of the ring-to-electrodes coupling strength, magnetic flux and
gate voltage. Our theoretical study shows that, for $\phi=\phi_0/2$
($\phi_0=ch/e$, the elementary flux-quantum) a high output current (1) (in the
logical sense) appears if the input to the gate is low (0), while a low output
current (0) appears when the input to the gate is high (1). It clearly exhibits
the NOT gate behavior and this aspect may be utilized in designing an
electronic logic gate.
