The operation of microelectronic circuits is described by classical laws that govern the macroscopic world. These laws are profoundly changed for phenomena occurring at the atomic scale: the world of atoms and molecules is determined by quantum mechanics. Superconducting nanocircuits provide a bridge between these two worlds. Although these nanocircuits are at the macroscopic scale (as they include some thousand atoms) the occurring physics obeys the laws of quantum mechanics. Therefore superconducting nanocircuits constitute model systems for quantum mechanics and quantum nanoelectronics. In particular they appear also as promising candidates as quantum bits for quantum information processing.
We are studying the quantum properties of a dc SQUID. Depending on the working point, this « artificial atom » demonstrates multilevel quantum or two level dynamics. In this limit it is used to realize a superconducting phase qubit. Read more
We have studied a circuit consisting of a Cooper pair transistor in parallel with a dc SQUID. This circuit realizes a tunable coupling between a charge qubit and a phase qubit. Read more
Topological protected qubit
We would like to realize a novel class of topologically protected qubits with Josephson junction circuits based on rhombi chains. These qubits would have a much longer coherence time than current superconducting qubits due to special symmetry reasons of the system. Read more
Superconducting Cooper-pairs pump
Quantum circuits can be tunned adiabatically using gate voltages and magnetic fluxes. When the circuit state can be "wound" adiabatically around quantum degeneracies an integer number of charges can be transferred. We use this exact topological quantization to make a Cooper pair pump which has metrological accuracy.
By using quasiparticle tunnelling in a superconducting-insulator-normal junction we cool down the electrons and phonons of a small metal island below the bath temperature. Read more