Quantum
Engineering
of Superconducting Qubits
William D.
Oliver
MIT Lincoln
Laboratory &
MIT Department of Physics
Superconducting
qubits are coherent artificial
atoms assembled from electrical circuit elements and microwave
optical
components. Their lithographic scalability, compatibility with
microwave
control, and operability at nanosecond time scales all
converge to make the
superconducting qubit a highly attractive candidate for the
constituent logical
elements of a quantum information processor.
In this talk, we
revisit the design,
fabrication, and control of the superconducting flux qubit. By
adding a high-Q capacitor, we
dramatically improve its
reproducibility, anharmonicity, and coherence, achieving T1
= 55 ms and T2
= 90 ms. We identify
quasiparticles as a
leading cause of temporal variability in the T1. We
introduce and
demonstrate a stochastic control technique that effectively
pumps away these
quasiparticles and thereby stabilizes and improves T1.
We also
discuss our demonstrations of 3D integration – bump bonding
and through silicon
vias – required for larger scale circuit realizations.
For more
information:
[1] J.
Bylander, et al., Nature
Physics 7, 565 (2011)
[2]
W.D. Oliver & P.B.
Welander, MRS Bulletin 38, 816 (2013)
[3] F.
Yan et al., Nature
Communications 7, 12964 (2016)
[4] S.
Gustavsson et al., Science
354, 1573 (2016)
[5] D.
Rosenberg et al., in
press, npj Quantum Information (2017); arXiv:1706.04116