Amplifying quantum signals with the single-electron transistor

S. L. Pohlen, Richard J. Fitzgerald, J. M. Hergenrother +1 more

We have developed a cryogenic voltage amplifier using GaAs metal semiconductor field effect transistors and coupled it to a superconducting single-electron transistor (SET) inside a dilution refrigerator. With this amplifier, we could extend the maximum output frequency of the SET, normally less than a kilohertz, up to 1 MHz. By placing this amplifier off-chip, we could maintain the low SET temperature required for proper SET operation.

Biaoyan Hu, G. M. Jones, A. S. Mampahzy +3 more

Ch. Obermair, Fangqing Xie, Th. Schimmel

Lisa A Tracy, Dwight Luhman, Stephen M Carr +6 more

We use a cryogenic high-electron-mobility transistor circuit to amplify the current from a single electron transistor, allowing for demonstration of single shot readout of an electron spin on a single P donor in Si with 100 kHz bandwidth and a signal to noise ratio of ∼9. In order to reduce the impact of cable capacitance, the amplifier is located adjacent to the Si sample, at the mixing chamber stage of a dilution refrigerator. For a current gain of ∼2.7×103, the power dissipation of the amplifier is 13 μW, the bandwidth is ∼1.3 MHz, and for frequencies above 300 kHz the current noise referred to input is ≤70 fA/Hz. With this amplification scheme, we are able to observe coherent oscillations of a P donor electron spin in isotopically enriched 28Si with 96% visibility.

Hsi‐Sheng Goan

Oleg G. Turutanov, A. M. Korolev, V. I. Shnyrkov +6 more

The requirements and details of designing a measuring cell and low-back-action deeply-cooled amplifier for quantum measurements at 10 mK are discussed. This equipment is a part of a microwave single-photon counter based on a superconducting flux qubit. The high-electron mobility transistors (HEMTs) in the amplifier operate in unsaturated microcurrent regime and dissipate only 1 μW of dc power per transistor. Simulated amplifier gain is 15 dB at 450 MHz with a high-impedance (≈ 5 kΩ) signal source and standard 50-Ω output.