Ultra-fast and low-noise homemade cryogenic transimpedance amplifier for spin-qubit read-out

While radio-frequency reflectometry and circuit-quantum-electrodynamics spin-qubit read-out techniques are promising for large qubit arrays [1], they are challenging to implement for quickly benchmarking new qubit materials and geometries. Cryogenic current amplifiers for fast charge sensing reported in 2007 [2] have a measurement bandwidth similar to the current reflectometry setups. Here we report on home-made GaAs HEMT-based, low-noise cryogenic transimpedance amplifiers with low power consumption of 2mW.

When the feedback resistance R_FB = 50 kΩ is used, our amplifier installed on the 4 K plate of a dilution refrigerator has the noise floor of 8e-27 A²/Hz with frequency bandwidth f_BW = 28 MHz. By using a higher R_FB, the noise floor is lowered further at the cost of smaller f_BW. We used our amplifier for a time-domain measurement of a 2 nA input square wave signal, typical for qubit charge sensors. In the case of R_FB = 200 kΩ (f_BW = 10 MHz), we measured a signal-to-noise ratio of 13 with 110pA_rms noise, which is promising for fast spin-qubit read-out.

We acknowledge funding from the Japan Society for the Promotion of Science KAKENHI (Grant No. JP19H05603 and JP21H01022) and JST PRESTO (Grant No. JP17940407).

 

[1] npj Quant. Inf. 3, 34 (2017)

[2] Appl. Phys. Lett. 91, 123512 (2007)