  We consider a system of two qubits at the ends of a finite length 1D cavity.
This problem is mapped onto the double-Kondo model which is also shown to
describe the low energy physics of a finite length quantum wire with resonant
levels at its ends. At the Toulouse point the ground state energy and the
average populations and correlations of the qubits or resonant levels at zero
temperature are computed. These results show that the effective interactions
between the qubits or resonant levels can be used to probe their associated
Kondo length scale.
