Asymmetry with respect to the magnetic field direction in the interaction between the quantum states of two coupled superconducting rings

The interaction between the quantum states of two circularly asymmetric superconducting aluminum rings forming figure eight, threaded by a magnetic flux and biased by an external sinusoidal ac current with zero dc component, has been investigated. Quantum oscillations in the dependence V _dc(B) of the rectified dc voltage on magnetic field for these structures have been measured at different external currents and temperatures close to critical. Fourier and wavelet analyses of the function V _dc(B) have revealed, along with the two fundamental ring frequencies, various combination frequencies; this fact is indicative of interaction in the structure. Deviation of the function V _dc(B) from oddness with respect to the magnetic field direction has been found for the first time.