Single-Shot Readout Performance of Two Heterojunction-Bipolar-Transistor Amplification Circuits at Millikelvin...

Area of Science:

• Quantum Computing
• Solid-State Physics

Background:

• High-fidelity single-shot readout of spin qubits is essential for quantum error correction.
• Cryogenic amplification improves readout fidelity and bandwidth (BW) by amplifying qubit signals before room-temperature amplification.

Purpose of the Study:

• To compare the performance of two cryogenic amplification circuits: current-biased heterojunction bipolar transistor (CB-HBT) and AC-coupled HBT (AC-HBT).
• To evaluate their suitability for high-fidelity, high-bandwidth spin qubit readout.

Main Methods:

• Two cryogenic amplifier circuits (CB-HBT and AC-HBT) were mounted on a dilution refrigerator's mixing-chamber stage.
• These circuits were connected to silicon metal oxide semiconductor (Si-MOS) quantum dot devices.
• Performance metrics including power dissipation, noise spectral density, and charge sensitivity were measured.

Main Results:

• Both CB-HBT and AC-HBT circuits exhibited low input noise spectral density (15-30 fA/√Hz).
• Charge sensitivities were 330 μe/√Hz for CB-HBT and 400 μe/√Hz for AC-HBT.
• Both circuits enabled single-shot readout with bit error rates below 10⁻³ in under 10 μs.

Conclusions:

• Both CB-HBT and AC-HBT cryogenic amplifiers meet the speed requirements for quantum error correction.
• These amplifiers offer a viable solution for high-fidelity, high-bandwidth spin qubit readout in quantum computing applications.