Radio-frequency single-electron transistor as readout device for qubits: charge sensitivity and backaction

Area of Science:

• Quantum computing
• Solid-state physics
• Nanotechnology

Background:

• Charge qubits are promising for quantum computation but require sensitive readout.
• Radio-frequency single-electron transistors (rf-SETs) offer high sensitivity for detecting charge states.

Purpose of the Study:

• To evaluate the rf-SET as a readout device for charge qubits.
• To quantify the charge sensitivity and backaction of the rf-SET.
• To compare measurement time with qubit decoherence time.

Main Methods:

• Fabrication and characterization of an rf-SET.
• Measurement of rf-SET charge sensitivity.
• Assessment of rf-SET backaction on a Cooper-pair box qubit.

Main Results:

• Achieved a charge sensitivity of 6.3 micro-electrons/sqrt(Hz).
• Demonstrated minimal backaction of the rf-SET on the Cooper-pair box.
• Determined that qubit mixing time can exceed measurement time.

Conclusions:

• rf-SETs are suitable for high-fidelity charge qubit readout.
• Single-shot qubit state measurement is feasible with this technique.
• This readout method minimizes qubit state disturbance.