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Cross-correlation noise measurements of a graphene-based SQUID magnetometer

Research output: Contribution to Journal/MagazineMeeting abstract

<mark>Journal publication date</mark>2019
<mark>Journal</mark>APS March Meeting 2019
Publication StatusPublished
<mark>Original language</mark>English


Lateral superconductor/graphene structures can be used to make Josephson junctions with low contact resistances and gate-tuneable critical currents. These junctions have the potential to provide new functionality for superconducting devices. For most devices, e.g. transmon qubits and SQUID sensors, it is important to quantify the intrinsic noise of the junctions. The voltage noise of low resistance junctions is typically below the noise floor of room temperature amplifiers. By cross-correlating the signals from two parallel amplifiers, we can detect signals down to 100 pV/√Hz, well below the noise floor of each amplifier. Using this technique, we characterise the voltage noise of a NbTi DC SQUID with graphene junctions in a frequency range from Hz to kHz. Combined with measurements of the SQUID's gain, we map its sensitivity across a range of operating conditions and find that the best-case sensitivity of the device is similar to traditional low temperature SQUIDs with oxide tunnel junctions. This project has received funding from the European Union's Horizon 2020 research and innovation programme under Grant agreement No 785219.