The unusual ground state doublet of the ²²⁹Th nucleus with the low energy M1(8.4 eV) transition between the nuclear states and the electron shell of the thorium ions with the similar electron transition represent two qubits spatially inserted one within the other. In the case of approximate equality of the energies of these transitions, weakly damped oscillations can be excited between these qubits, namely, multiple coherent energy transfer from the electron shell to the nucleus and vice versa. Due to the relatively high interaction energy of the electron and nuclear currents this process in the ²²⁹Th ions does not require resonant coincidence of the transition energies. The electron shell, transitioning between two electron states, “breathes”, periodically decreasing and increasing in size and plays the role of a kind of resonator for the virtual photon emitted by the nucleus.

Fig. Multiple exchange of excitation energy between the nucleus and its electron shell.

E.V. Tkalya
JETP Letters 124, issue 5 (2026)