Graphene-based tunable SQUIDs

• Published in: Applied physics letters Vol. 110; no. 16
• Main Authors: Thompson, M. D., Ben Shalom, M., Geim, A. K., Matthews, A. J., White, J., Melhem, Z., Pashkin, Yu. A., Haley, R. P., Prance, J. R.
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 17-04-2017
• Subjects: Adaptive control; Applied physics; Electrical junctions; Graphene; Josephson junctions; Low noise; Magnetometers; Proximity effect (electricity); Qubits (quantum computing); Superconducting quantum interference devices; Superconductivity
• ISSN: 0003-6951; 1077-3118
• DOI: 10.1063/1.4981904

The superconducting proximity effect in graphene can be used to create Josephson junctions with
critical
currents that can be tuned using local field-effect gates. These
junctions
have the potential to add functionality to existing technologies; for example,
superconducting quantum
interference device
(SQUID)
magnetometers with adaptive dynamic range and superconducting qubits with fast electrical
control. Here, we present measurements of graphene-based superconducting quantum interference
devices incorporating ballistic
Josephson
junctions that can be controlled individually. We investigate the
magnetic field
response of the SQUIDs as the junctions are gated and as the device is tuned between
symmetric and asymmetric configurations. We find a highest transfer
function ≈ 300 μV/Φ0, which compares favorably with conventional, low
temperature DC SQUIDs. With low noise readout electronics and optimised geometries,
devices based on
ballistic
graphene
Josephson
junctions have the potential to match the sensitivity of traditional
SQUIDs while
also providing additional functionality.