Exact low-energy duality in superconducting quantum circuits

These systems exhibit a superconducting-to-insulating quantum phase transition driven by the impedance of the environment, known as the Schmid-Bulgadaev phase transition. The authors show that the critical point is universal and does not depend on the microscopic properties of the junction, in particular on the ratio of its Josephson and charging energies.

This result extends earlier approximate duality mappings between the Cooper-pair tunneling regime and the phase-slip regime, which have recently been debated. The exact duality is established through analytical arguments supported by exact diagonalization calculations comparing circuits with different boundary conditions that become equivalent in the large-size limit.

These findings help resolve recent controversies on the Schmid-Bulgadaev transition and provide a new framework to identify critical behavior in quantum impurity problems and superconducting circuits.

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Contact : Cristiano Ciuti