Radiofrequency cascade readout of coupled spin qubits

Area of Science:

• Quantum computing
• Semiconductor device physics
• Quantum information science

Background:

• Silicon spin qubits offer a scalable path to quantum processing due to compatibility with semiconductor manufacturing.
• Current spin readout methods, like proximal charge sensors, introduce architectural complexity and limit qubit connectivity.
• In situ dispersive readout techniques are more compact but suffer from limited sensitivity.

Purpose of the Study:

• To develop a more sensitive and compact in situ readout technique for silicon spin qubits.
• To overcome the sensitivity limitations of existing dispersive readout methods.
• To enable faster and more scalable quantum information processing in silicon.

Main Methods:

• A novel radiofrequency electron-cascade readout method was employed.
• The technique utilizes alternating-current electron co-tunnelling to enhance the dispersive signal.
• Demonstrated on a natural silicon planar metal-oxide-semiconductor (MOS) quantum dot array.

Main Results:

• Achieved a signal-to-noise ratio enhancement of over 35 dB.
• Reduced minimum integration time to 7.6 ± 0.2 µs.
• Demonstrated high-fidelity singlet-triplet readout and coherent spin control via exchange interaction.

Conclusions:

• The radiofrequency electron-cascade readout significantly enhances qubit performance.
• This method paves the way for scalable quantum computing architectures in silicon.
• Achieved long dephasing times (up to 500 ns) and a high gate quality factor (>10).