  The interaction between the quantum states of two aluminum superconducting
rings forming an 8-shape circular-asymmetric microstructure was examined under
a threading magnetic flux and bias by an alternating current without a dc
component. Quantum oscillations of the rectified dc voltage Vdc(B) as a
function of magnetic field were measured in the 8-shape microstructure at
various bias ac currents and temperatures close to critical. Fourier and
wavelet analyses of Vdc(B) functions revealed the presence of various
combination frequencies in addition to two ring fundamental frequencies, which
suggests the interaction in the structure. Deviation of the Vdc(B) function
from oddness with respect to the magnetic field direction was found for the
first time.
