Superconducting tetrahedral quantum bits

Superconducting quantum bits have established themselves as promising candidates for the solid-state implementation of quantum information processors. Further advances in their performance can be achieved through new designs implying better noise protection, relieved fabrication constraints, variability and ease of manipulation, and optimized readout through single-shot measurements. Exploiting symmetry and frustration, we introduce a new type of quantum bit embodying all these advantages. We propose a structure involving four superconducting islands in the topology of a symmetric tetrahedron, uniformly frustrated with one-half flux-quantum per loop and one-half Cooper-pair per island. This structure emulates a noise-resistant spin-1/2 system in a vanishing magnetic field. Symmetry arguments indicate that this tetrahedral quantum bit exhibits the minimal complexity needed to combine the above benefits with a doubly degenerate ground state, the latter being advantageous for quantum computing. Variability of manipulation and optimized readout are additional benefits of this design.