  We address XOR gate response in a mesoscopic ring threaded by a magnetic flux
$\phi$. The ring, composed of identical quantum dots, is symmetrically attached
to two semi-infinite one-dimensional metallic electrodes and two gate voltages,
viz, $V_a$ and $V_b$, are applied, respectively, in each arm of the ring which
are treated as the two inputs of the XOR 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-electrodes coupling strengths, magnetic flux and gate voltages.
Quite interestingly it is observed 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 one, and only one, of the inputs to the gate is high (1), while if
both inputs are low (0) or both are high (1), a low output current (0) appears.
It clearly demonstrates the XOR behavior and this aspect may be utilized in
designing the electronic logic gate.
