The flux qubit revisited to enhance coherence and reproducibility.
The scalable application of quantum information science will stand on reproducible and controllable high-coherence quantum bits (qubits). Here, we revisit the design and fabrication of the superconducting flux qubit, achieving a planar device with broad-frequency tunability, strong anharmonicity, high reproducibility and relaxation times in excess of 40 μs at its flux-insensitive point. Qubit relaxation times T1across 22 qubits are consistently matched with a single model involving resonator loss, ohmic charge noise and 1/f-flux noise, a noise source previously considered primarily in the context of dephasing. We furthermore demonstrate that qubit dephasing at the flux-insensitive point is dominated by residual thermal-photons in the readout resonator. The resulting photon shot noise is mitigated using a dynamical decoupling protocol, resulting in T2≈85 μs, approximately the 2T1limit. In addition to realizing an improved flux qubit, our results uniquely identify photon shot noise as limiting T2in contemporary qubits based on transverse qubit-resonator interaction.
Research Laboratory for Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Fei
F
Yan
Research Laboratory for Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Simon
S
Gustavsson
Research Laboratory for Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Archana
A
Kamal
Department of Physics, University of California, Berkeley, California 94720-7300, USA.
Jeffrey
J
Birenbaum
MIT Lincoln Laboratory, Quantum Information and Integrated Nanosystems Group, 244 Wood Street, Lexington, Massachusetts 02420, USA.
Adam P
AP
Sears
MIT Lincoln Laboratory, Quantum Information and Integrated Nanosystems Group, 244 Wood Street, Lexington, Massachusetts 02420, USA.
David
D
Hover
MIT Lincoln Laboratory, Quantum Information and Integrated Nanosystems Group, 244 Wood Street, Lexington, Massachusetts 02420, USA.
Ted J
TJ
Gudmundsen
MIT Lincoln Laboratory, Quantum Information and Integrated Nanosystems Group, 244 Wood Street, Lexington, Massachusetts 02420, USA.
Danna
D
Rosenberg
MIT Lincoln Laboratory, Quantum Information and Integrated Nanosystems Group, 244 Wood Street, Lexington, Massachusetts 02420, USA.
Gabriel
G
Samach
MIT Lincoln Laboratory, Quantum Information and Integrated Nanosystems Group, 244 Wood Street, Lexington, Massachusetts 02420, USA.
S
S
Weber
MIT Lincoln Laboratory, Quantum Information and Integrated Nanosystems Group, 244 Wood Street, Lexington, Massachusetts 02420, USA.
Jonilyn L
JL
Yoder
Research Laboratory for Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.|Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Terry P
TP
Orlando
Department of Physics, University of California, Berkeley, California 94720-7300, USA.
John
J
Clarke
MIT Lincoln Laboratory, Quantum Information and Integrated Nanosystems Group, 244 Wood Street, Lexington, Massachusetts 02420, USA.
Andrew J
AJ
Kerman
Research Laboratory for Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.|MIT Lincoln Laboratory, Quantum Information and Integrated Nanosystems Group, 244 Wood Street, Lexington, Massachusetts 02420, USA.|Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
William D
WD
Oliver