Arxiv 2512.17050

This year, the Nobel Prize 2025 was awarded to an international team of two experimentalists, British-born John Clarke and American John M. Martinis, and a theoretician from France, Michelle H. Devoret, all worked together at the University of California, “for the discovery of macroscopic quantum tunneling and the quantization of energy in an electrical circuit” [1]. Quantum mechanics has recently turned 100, but the potential of its revolutionary ideas is far from exhausted. In 1957, the BCS quantum mechanical theory of superconductivity was developed, for which the authors, John Bardeen, Leon Cooper, and John Robert Schrieffer, also received the Nobel Prize in 1972. According to it, a single Bose condensate with a common complex wave function is formed in a superconductor due to the weak attraction between electrons caused by the phonon exchange. The coherence of this wave function is preserved even if the superconductor is interrupted by a thin dielectric layer, which was in doubt from the point of view of many researchers at the time until Brian Josephson theoretically proved this in 1962. Unexpectedly, the probability of the Cooper pair tunneling turned out to be anomalously high, almost the same as for single electrons. (Cooper pairs, as one might simplistically assume, constitute a superconducting condensate; although, strictly speaking, the BCS theory considers many-particle interactions.) This phenomenon is known as the stationary Josephson effect. According to his theory, the maximum possible superconducting current through a tunnel junction is proportional to the sine of the condensate wave function phase difference between the two parts of the superconductor. Thus, the phase of the wave function transformed from a purely theoretical quantity into a real one measurable through the superconducting current. Josephson also derived a second, non-stationary, effect that relates the frequency of current oscillations in such a junction to the constant voltage across it, if the critical current of the junction is exceeded. For these two predictions, he received the Nobel Prize in 1973. Shortly after, both effects were confirmed experimentally. Note that extremely weak picowatt radiation from a Josephson junction with a frequency of about 10 GHz (three-centimeter frequency range, X-band) was first experimentally observed at the B. I. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine (ILTPE) by Ukrainian scientists I. K. Yanson, V. M. Svistunov, and I. M. Dmitrenko in 1965 [2]. Almost simultaneously, two months later, the American team D.