Superconducting materials are a natural choice for building solid-state quantum circuits, since superconductivity offers coherence. Superconductors have a region in the energy spectrum, in which only one energy level exists, the Fermi level, while all other energy levels are separated from it by the superconducting energy gap. Cooper pairs of conducting electrons condense to this energy level, which appears to be protected from low-energy excitations because of the presence of the gap. This allows to prepare, control and manipulate quantum states in superconductor-based nanostructures for the use in various devices whose operation is based upon quantum principles.

In my presentation, I will cover several experiments in which superconducting nanocircuits with a charge degree of freedom were used as solid-state qubits [1,2] and charge pumps [3]. I will also outline the plans of my group to investigate hybrid devices in which mechanical degrees of freedom are strongly coupled to the superconducting condensate.

[1] Y. Nakamura, Yu.A. Pashkin, and J.S. Tsai, Nature 398, 786 (1999).
[2] Yu.A. Pashkin et al., Nature 421, 823 (2003).
[3] J.P. Pekola et al., Rev. Mod. Phys. 85, 142 (2013).