SQUIDs based set-up for probing current noise and correlations in three-terminal devices

We have implemented a new experimental set-up for precise measurements of current fluctuations in three-terminal devices. The system operates at very low temperatures (30 mK) and is equipped with three SQUIDs as low noise current amplifiers. A SQUID input coil is connected to each terminal of a sample allowing the acquisition of time-dependent current everywhere in the circuit. From these traces, we can measure the current mean value, the noise and cross-correlations between different branches of a device. In this paper we present calibration results of noise and cross-correlations obtained using low impedance macroscopic resistors. From these results we can extract the noise level of the set-up and show that there are no intrinsic correlations due to the measurement scheme. We also studied noise and correlations as a function of a DC current and estimated the electronic temperature of various macroscopic resistors.

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