Materials Research for Improved Josephson Junction Qubits
Abstract
The current-biased Josephson junction is an attractive candidate for a quantum bit. Recent results suggest that decoherence is dominated by quantum mechanical coupling of the junction to resonant defects in the oxide tunnel barrier. Progress in the field of superconducting qubits will therefore require deep understanding of materials issues and exploration of novel techniques for junction growth and fabrication. Here we present preliminary results on the fabrication and characterization of Al-AlOx-Al trilayer tunnel junctions for qubits. The trilayer junctions display subgap currents which are an order of magnitude lower than those for junctions fabricated with an ion-mill clean of the base electrode, suggesting a larger number of conduction channels with a relatively low transmission probability. When operated as qubits, the trilayer junctions show smaller resonant splittings in cw spectroscopy, and coherence times in excess of 80 ns. Finally, we describe ongoing efforts to fabricate qubits from UHV-grown trilayers which involve crystalline electrodes and crystalline tunnel barriers.
- Publication:
-
APS March Meeting Abstracts
- Pub Date:
- March 2004
- Bibcode:
- 2004APS..MARA37005M