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arXiv · 1301.3184

A dispersive nanoSQUID magnetometer for ultra-low noise, high bandwidth flux detection

E. M. Levenson-Falk·R. Vijay·N. Antler·I. Siddiqi
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Abstract

We describe a dispersive nanoSQUID magnetometer comprised of two variable thickness aluminum weak-link Josephson junctions shunted in parallel with an on-chip capacitor. This arrangement forms a nonlinear oscillator with a tunable 4-8 GHz resonant frequency with a quality factor Q = 30 when coupled directly to a 50 $Ω$ transmission line. In the presence of a near-resonant microwave carrier signal, a low frequency flux input generates sidebands that are readily detected using microwave reflectometry. If the carrier excitation is sufficiently strong then the magnetometer also exhibits parametric gain, resulting in a minimum effective flux noise of 30 n$Φ_0$/Hz$^{1/2}$ with 20 MHz of instantaneous bandwidth. If the magnetometer is followed with a near quantum-noise-limited Josephson parametric amplifier, we can increase the bandwidth to 60 MHz without compromising sensitivity. This combination of high sensitivity and wide bandwidth with no on-chip dissipation makes this device ideal for local sensing of spin dynamics, both classical and quantum.

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E. M. Levenson-Falk, R. Vijay, N. Antler, I. Siddiqi. 2013-01-14. A dispersive nanoSQUID magnetometer for ultra-low noise, high bandwidth flux detection. https://doi.org/10.1088/0953-2048%2F26%2F5%2F055015

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