A superconducting-phase quantum bit (qubit) involves three or more Josephson junctions combined into a superconducting loop and defines one of the promising solid-state device implementations for quantum computing. Recently, so called π junctions, Josephson junctions with a ground state characterized by a π-phase shift across, have attracted much attention. We show how to make use of such π junctions in the construction of superconducting phase qubits and discuss the advantage over conventional designs based on magnetically frustrated loops. Starting from a basic five-junction loop with one π junction, we show how to construct effective junctions with degenerate minima characterized by phase shifts 0 and π and superconducting-phase switches. These elements are then combined into a superconducting-phase qubit which operates exclusively with switches, thus avoiding permanent contact with the environment through external biasing. The resulting superconducting-phase qubits can be understood as the macroscopic analog of the "quiet" s-wave-d-wave-s-wave Josephson-junction qubits introduced by Ioffe et al.
|Original language||English (US)|
|Number of pages||9|
|Journal||Physical Review B - Condensed Matter and Materials Physics|
|Publication status||Published - Jan 1 2001|
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics