We have incorporated a single crystal silicon shunt capacitor into a Josephson phase qubit. The capacitor is derived from a commercial silicon-on-insulator wafer. Bosch reactive ion etching is used to create a suspended silicon membrane; subsequent metallization on both sides is used to form the capacitor. The superior dielectric loss of the crystalline silicon leads to a significant increase in qubit energy relaxation times. T1 times up to 1.6 micro-second were measured, more than a factor of two greater than those seen in amorphous phase qubits. The design is readily scalable to larger integrated circuits incorporating multiple qubits and resonators.
@article{arxiv.1210.1545,
title = {Coherent Josephson phase qubit with a single crystal silicon capacitor},
author = {U. Patel and Y. Gao and D. Hover and G. J. Ribeill and S. Sendelbach and R. McDermott},
journal= {arXiv preprint arXiv:1210.1545},
year = {2015}
}